A PP E NDIX 7A: GEOLOGY

APPENDIX 7B: HISTORY

APPENDIX 7C: MINING HISTORY

o j tlu* Animus /iu vr' A PP E N D I X 7 A

O verview of Geology Anim as River W atershed Above Silverton

Prepared for the Animas River Stakeholders Group Use Attainability Analysis

Prepared By B.K Stover Colorado Division of Minerals and Geology VOLCANIC HISTORY OF THE SILVERTON CALDERA

Water Quality

Bedrock Geology Precambrian Metamorphic Roclcs Paleozoic Sedimentary Rocks Upper Paleozoic And Mesozoic Sedimentary Rocks ' Tertiary Sedimentary Rocks Tertiary Volcanic Rocks

Surficial Geology

Structural Geology

nydrothcrmal Alteration

CEMENT CREEK SUB-BASTN

Stratigraphy

Structural Geology

nydrothcrmal Alteration

Surficial Geology

ROSS BASIN WATERSHED

Bedrock Geology

Structural Geology

Itydrothermal Alteration

Ore Mineralization

Surficial Geology

CEMENT CREEK-BONITA PEAK WATERSHED AREA

Bedrock Geology

Structural Geology

Hydrothermal Alteration

Ore Mineralization

Surficial Geology SOUTH FORK CEMENT CREEK AREA 19

Location 19

Bcdrock Geology 19

Structural Geology 19

Hydrothermal Alteration 20

Ore Mineralization 20

Surficial Geology 20

PROSPECT GULCII-GEORGIA GULCH AREA 21

Location 21

Geologic Setting 21

Bedrock Geology 21

Structural Geology 22

Hydrothermal Alteration 22

Ore Mineralization 22

Surficial Geology 23

LOWER CEMENT CREEK AREA 24

Location 24

Geologic Setting 24

Bedrock Geology 24

Structural Geology 24

Hydrothermal Alteration 24

Ore Mineralization 25

Surficial Geology 25

ANIMAS RIVER HEADWATERS AND BURROWS CREEK 26

Location 26

Geologic Setting 27 CALIFORNIA GULCH 28

Location 28

Geologic Setting

Surficial Geology 29

PLACER GULCH 29

Location ^

Geologic Setting

Surficial Geology 30

ANIMAS RIVER SITES, ( ANIMAS FORKS TO EUREKA) 30

Location 30

Geologic Setting 3*

EUREKA GULCH 31

Location 3*

Geologic Setting 31

MINNIE GULCn 32

Geologic Setting 32

Surficial Geology 33

Geologic Hazards 33

MAGGIE GULCH 33

Location 33

Geologic Setting 33

Surficial Geology 33

CUNNINGHAM GULCH 33

Location 33

Geologic Setting 3^ Surficial Geology 35

ARRASTRA BASIN 35

Location 35

Geologic Setting 35

Surficial Geology 37

ANIMAS RIVER SITES 37

Location 37

Geologic Setting 37

Surficial Geology 39

MINERAL CREEK SITES 3 9 LONGFELLOW-KOEHLER 39

Location 39

Geologic Setting 39

Bedrock Geology 39

Structural Geology 40

Surficial Geology 40

BONNER MINE 40

Location 40

Geological Setting 41

Bedrock Geology 41

Structural Geology 41

Surficial Geology 41

Mine Feature 41

RUBY TRUST 42

Location 42

Geologic Setting 42 Bcdrock Geology 42

Structural Geology 42

Surficial Geology 43

PARADISE MINE 43

Location 43

Geologic Setting43 43

Bcdrock Geology 43

Structural Geology 43

Surficial Geology 44

BANDORA MINE 44

Location 44

Geologic Setting 44

Bedrock Geology 44

Surficial Geology 44

NORTH STAR MINE 45

Location 45

Geologic Setting 45

Bedrock Geology 45

Structural Geology 45

CARBON LAKE 46

Location 46

Geologic Setting 46

Bedrock Geology 46

Structural Geology 46

Surficial Geology 47

REFERENCES 48 Overview of Geology Animas River Watershed Above Silverton By B.K Stover Colorado Division of Minerals and Geology

Volcanic History of the Silverton Caldera

The Animas River headwaters drain the Silverton Caldera, a Tertiary-aged volcanic center on the western margin of the regional San Juan Volcanic Field. In Oligocene through Miocene time, the Silverton Caldera was a focus of repeated volcanic eruptive activity. Hundreds of cubic miles of ash flows and lava were erupted upon a surface of older Paleozoic and Mesozoic sedimentary rock, and Precambrian metamorphic and igneous basement rocks. Through the middle Tertiary, an extensive, thick volcanic complex was formed, encompassing all the present Animas Basin watershed. During periods of volcanic quiescence, retreat of magma from beneath the domed-up center caused widespread subsidence and subsequent collapse of a roughly ten-mile-diameter ring-shaped caldera within the larger volcanic field. Subsequent periods of eruptive activity each caused renewed uplift and doming of the caldera, followed in turn by subsidence along the bounding ring-fauft fractures as volcanic activity waned. These repeatedly active marginal ring-fault fractures, associated breccia pipes, and swarms of antithetic faults tangential and radial to the margin of the caldera, formed preferential pathways for circulating mineralized hydrothermal fluids.

Following cessation of volcanic activity, ground and meteoric waters began infiltrating and circulating in the cooling mass of volcanic rock. Heat from the cooling magma below set up broad, regional convection systems, circulating hot hydrothermal fluids through the subsurface for millions of years. Through time, these fluids chemically altered the original rock mass, and became enriched in metals derived from the volcanic and surrounding pre-volcanic country rock. Eventually, mineralizing solutions reached threshold geochemical temperature-pressure conditions, leading to deposition of several types of sulfide ores containing silver, lead, zinc, copper, and gold. The sulfide ores were preferentially deposited within and around the pre-existing fissures, faults, and breccia pipes formed millions of years before. Much of the rock in the Silverton Caldera complex is therefore highly mineralized and hydrothermally altered, particulary along the margins of the caldera, and in the vicinity of major fissure vein systems.

Through the late Tertiary and to present day, regional uplift and subsequent erosion of the Colorado Plateau has cut deeply into the volcanic pile. Thousands of feet of overlying rock have been stripped away, revealing the roots of the volcanic center. Canyons around the margin of the caldera, such as the Animas River and Uncompahgre Gorge, have cut deeply into the underlying strata, exposing the underlying Paleozoic and Precambrian rock beneath the volcanic deposits.

Water Quality The headwaters of the Animas River begin within and along the margins of the Silverton Caldera. Two major tributaries draining this volcanic terrain, Mineral Creek and Cement Creek, carry excessive metals loading, joining the Animas River at Silverton just before it enters the narrow, steep walled canyon south of town. Water quality sampling in the Animas Basin around Silverton has shown that in-stream water quality can be directly correlated to the specific geologic, mineralogic, and rock alteration attributes present in a stream’s watershed. Rock type, primary mineralization suites, and both pre and post-mineralization hydrothermal alteration systems present in a watershed characterize the observed stream water quality, even in undisturbed watersheds. Analytical data shows that the overall stream water quality of the Animas and its tributary gulches on the eastern side of the Silverton Caldera is generally much better than the water quality of Cement Creek and Mineral Creek Watersheds. The South fork of Mineral Creek is nearly pristine, contrasting sharply with the metals laden waters of the main stem of Mineral Creek. There is a direct association between better in-stream water quality and the geologic differences in mineralization and alteration styles present in the individual gulches in the Animas Basin watershed.

Bedrock Geology

The Animas watershed drains roughly three-quarters of the total extent of the Silverton Caldera. Extrusive sequences of volcanic ash-flow tuffs and flow breccias, and dacite -to-rhyodacite lava flows and domes underlie essentially the entire watershed. These rocks belong to the Silverton Volcanic series, and underlying San Juan Formation. The Silverton series has been further subdivided into mapable formations in the Silverton Caldera. On the southern and eastern margins of the caldera, Paleozoic and older Precambrian rock are exposed beneath the volcanic flows. Intruded upward into the volcanic flows within the caldera, but particularly along its margins, are younger stocks, plugs, dikes, and sills of a variety of igneous rock.

The sequence of rocks underlying and exposed in the Animas watershed area are described here, from oldest to youngest (Ludeke and Burbank, 1987)

Precambrian Metamorphic Rocks

Irving Formation (Precambrian-X')- Metavolcanic and metasedimentry gneiss, quartzite, amphibolite, and schist “basement” rock underlies the volcanic flows and breccias of the Silverton series on the eastern and southern margins of the caldera. Exposures are limited to the lower valley walls at the head of Cunningham Gulch, in lower Stony Gulch, and just inside the mouth of the Animas Canyon at the Champion Mine. In the Animas Canyon area, an angular unconformable erosion surface forms the contact between the Precambrian Irving section and the overlying upper-Cambrian Ignacio Quartzite. The erosion surface can be traced along the west canyon walls downstream of the Champion Mine. It is characterized by a smooth, undulating surface carved in the metasedimentary Irving Formation, beneath a quartz-cobble and pebble conglomerate at the base of the Ignacio sediments. Locally, the Precambrian contact has been structurally offset several feet across younger vein/ dike structures associated with the granite- porphyry intrusive on the flanks of Sultan Mountain, indicating a dilative emplacement of the intrusive. Compositional layering ofthe underlying Irving metamorphic complex is sharply discordant to the overlying Cambrian sediments and Silverton Volcanic sequence,

Paleozoic Sedimentary Rocks

Leadville Limestone. Ourv Limestone and Elbert Formation, and the Ignacio Quartzite (Cambrian to Mississippian)- A narrow section of lower Mississippian, upper Devonian and upper Cambrian sedimentary rock is exposed in a steeply plunging narrow band on the Animas Canyon walls in the vicinity of the Champion Mine, and in small isolated outcrops on the valley walls of Cunningham Gulch above the Highland Mary Mill site. This thin remnant of the basal Paleozoic section is buried under the alluvial valley floor of the Animas River where it crosses beneath the axis of the valley at the Champion Mine. The section continues in a narrow band along the south-western slopes of Kendall Mountain on the east side ofthe canyon, between the 7 Precambrian Irving group and the overlying volcanic tuffs and flow-rocks of the Silverton Series which form Kendall Mountain. There are numerous pits and quarries in the carbonate members of the section on Kendall Mountain, as well as at the quarry above the Highland Mary Mill. The Ignacio Quartzite can be traced along a Precambrian angular-unconformity in the cliffs above the Animas Canyon all the way to Elk Park, but is absent in the Cunningham and Stony Gulch exposures. Paleozoic rocks have been intruded and cut by the Sultan Mountain quartz-monzonite (described below). Outcrops along Highway 550 expose a brecciated, veined contact margin with the stock and associated dikes and sills. Paleozoic rocks show contact metamorphism along the margins of the intrusive. Sedimentary strata at the intrusive contact are commonly highly altered, iron-stained, manganese stained, and impregnated with abundant limonite, hematite and other secondary alteration minerals.

Upper Paleozoic And Mesozoic Sedimentary Rocks

In the Animas watershed above Silverton, upper Paleozoic and Mesozoic sedimentary rocks are exposed only in the South Fork of Mineral Creek. The section crops out on both valley walls west of the confluence with Mineral Creek, beneath the overlying Tertiary volcanic San Juan Formation, and in parts of the upper headwaters. This sedimentary section includes:

Cutler Formation (Lower Permian)- Terrestrial red shales, siltstones, mudstone and arkosic conglomerates. Broad exposures of these “red beds” can be seen on both valley walls of the South Fork of Mineral Creek.

Dolores Formation (Upper Triassic )- Terrestrial red shales, siltstone, sandstone, and limestone-pebble conglomerates; outcrops in a narrow band above the Cutler beds on the valley walls of the South Fork of Mineral Creek. Waneka and Entrada Formations (Upper Jurassic)- Light gray cross-bedded sandstone and limy shale and siltstone, exposed only in a thin, discontinuous band above the Dolores formation in the upper valley of the South Fork of Mineral Creek.

Morrison Formation (Upper Jurassic)-Varigated, thin-bedded claystone and mudstone in upper part, sandstone and interbedded claystone and mudstone in lower part; exposed only in the upper watershed of South Fork of Mineral Creek, near the Bandora Mine.

Dakota Sandstone (Upper Cretaceous)- Light gray to brown sandstone with interbedded siltstone and carbonaceous shale, commonly with chert-pebble conglomerate near base; exposed only in two contact-metamorphosed outcrops in the vicinity of the Bandora Mine, on the South Fork of Mineral Creek.

Tertiary Sedimentary Rocks

Telluride Conglomerate (Eocene)- Conglomerate of pebbles, cobbles, and boulders derived from underlying Mesozoic, Paleozoic, and Precambrian rock. This unit represents the pre-volcanic surface upon which subsequent volcanic extrusive rocks were erupted during volcanic episodes in the middle Tertiary. In the Animas watershed above Silverton, the Telluride Conglomerate only outcrops in the valley walls of the South Fork of Mineral Creek, as a thin band beneath the overlying San Juan Formation. Tertiary Volcanic Rocks

Extrusive and Related Rocks

San Juan Formation (Oligocene)- Massive to thick-bedded gray and greenish-gray, red or purple mudflow breccias, with intermixed sandy tuffs and conglomerates, locally interbedded with thin flows of dacite and rhyobasalt. The formation consists of a propylitically altered, finely crushed matrix of volcanic debris, surrounding fragments to large blocks of andesite to rhyodacite volcanic rock. This unit outcrops over much of the area west of Mineral Creek, from the top of Red Mountain Pass to the upper valley walls of the South Fork of Mineral Creek. It represents the oldest volcanic sequence exposed in the Animas watershed.

Sapinero Mesa Tuff fQligocene')•■Subdivided into members as follows:

Outflow Sheet Facies (includes Blue Mesa Tuff)- A compositionally zoned ash-flow tuff ranging from moderately crystal-rich quartz-latite in the upper part and near-source, to crystal-poor rhyolite in the lower part. In the Animas watershed, this once extensive ash- flow sheet is now preserved only on the high peaks capping the drainage divide west of Red Mountain Pass and Mineral Creek.

Picayune Megabreccia Member -This sequence of fine-grained porphyritic andesite lava flows and flow breccias outcrops in the Animas River Canyon near the mouths of Picayune, Bums, and Grouse Gulches, downstream from Animas Forks. The unit is altered greenish-gray, and weathers brownish-gray. The flows are commonly amygdaloidal (contain gas cavities or vesicles filled by secondary minerals).

Eureka Rhvolite Tuff Member- (Intracaldera equivalent of the outflow Sapinero Mesa Tuff) A gray to greenish-gray welded ash-flow tuff of quartz latite to riiyolitic composition, with conspicuous eutaxitic structure (banded structure, resulting in a streaked or blotchy appearance). This tuff crops out in the lower part of California Gulch, the western side of Placer Gulch, the flanks of Houghton Mountain, and along the lower valley walls of most of the major gulches along the east side of the Animas River, from Horseshoe Creek to Maggie Gulch, and again in Arrastra Gulch. It also forms the lower southwestern slopes of Kendall Mountain.

Silverton Volcanics (Oligocene)- A sequence of predominantly intermediate composition lava flows and related volcaniclastic rocks were extruded onto the underlying Eureka Tuff in later Oligocene time. These volcanic flows have been subdivided into the following mapable formations exposed in the watershed, from oldest to youngest:

Bums Member- A sequence of light to dark-gray, thin to thick, intertounging flows and domes of poiphyritic dacite and rhyodacite overlies the Eureka Tuff. It crops out over about two-thirds of the entire watershed, including the mountainous area within the caldera margin, and on the high peaks east of the Animas River between Eureka and Silverton. These rocks have been propylitically altered throughout the watershed, (propylitic alteration described below). Rhvolite Unit- A prominently flow-laminated lava flow and associated tuffs found at the base of the overlying Andesite Member. This unit only occurs near the summits of the higher peaks and ridges in the watershed.

Andesite Member- A pyroxene andesite combined with the Henson Member. This unit is a brownish weathering, dark-gray, porphyritic andesite in thick to thin, commonly amygdaloidal lava flows and flow-breccias. It also can contain gray, black, and brown lenticular interbedded sandy and shaly tuffs, and locally, thin fresh-water limestones.

Ash-Flow Tuff of Crown Mountain (Oligocene)- An isolated outcrop of light-gray to dark-gray devitrified (glassy rock which, through time, has broken up into different minerals through solid state transformation), weakly to densely welded ash-flow tuff; composed of sparsely to moderately porphyritic rock with phenocrysts of quartz, feldspar, biotite, and some pyroxene, in a dense eutaxitic groundmass. This unit only occurs on the summit of Crown Mountain, above Niagra Gulch near Eureka.

Younger Intrusive Rocks Onartz-Monzonite (Granite) Porphyry (Oligocene-Miocene)- Hypabyssal (magma from deep down, but emplacement occurs below the surface) intrusive porphyritic quartz-monzonite stocks, dikes, sills and sheets intruded into the older volcanic flows and underlying Paleozoic and Precambrian rock along and concordant with the ring-faulted margin of the Silverton Caldera. At Silverton, the wide, patk-Iike valley occupied by the Animas River is underlain by a large body of this poiphyry. The intrusion underlies the valley and both sides of the river from Silverton to the narrow mouth of the Animas Canyon at the Champion Mine. Granite poiphyry also forms the northern slopes and summit of Sultan Mountain, Bear Mountain, and outcrops at the foot of Sultan Mountain from the Little Dora mine to the Champion mine, the northern half of Anvil Mountain, and along the east foot- slope of Kendall Mountain from Silverton to the mouth of the Animas Canyon. It is inferred to underlie the broad river valley at Silverton, beneath a relatively thick deposit of river alluvium. This same type of intrusive rock is also found in thick-to-ihin dikes and intrusions along the ring-fault zone in Mineral Creek, and high on the valley walls of lower Cunningham, Minnie, and Maggie Gulches. Dikes and plugs also occur on Kendall Mountain and in Arrastra Gulch. The strike of these dikes and bodies roughly parallels the ring-fault structure of the Silverton Caldera.

Rhvolite (Miocene and OligoceneV Dikes, sills, plugs, and irregular shaped masses of white to light-gray, dense to moderately porphyritic rhyolite have intruded the older Bums Member and Eurka Tuff at isolated locations throughout the watershed. The largest mass is intruded along a series of northeast trending faults at Denver Hill, and the northern foot of Houghton Mountain across from the London Mine, Quartz Latite Porphyry (Miocene and Oligocene)- Dikes, sheets, plugs, and irregular masses of light brown to gray, dense, aphanitic (crystal components invisible to the naked eye; glassy texture), to fine-grained rock with feldspar phenocrysts. This type of rock has intruded the older Eureka Tuff and Bums Formation at isolated locations along the margin of the caldera structure» most prominently at the Longfellow-Koehler Mine near Red Mountain Pass, and on Houghton and Wood Mountains near Animas Forks.

Surficial Geology The high alpine terrain in the Animas watershed has been deeply scoured and sculpted by glaciers during the past 40,000 years. Exposed bedrock outcrop with thin patchy soils covers an estimated 10 80% of the surface. Unconsolidated surficial deposits are generally confined to the valley floors, and consist of remnant patches and aprons of glacial till, outwash and stream alluvium, and peat and organic bog deposits in wetland areas on the flat-floored glacially carved valleys. Talus and scree deposits mantle extensive areas of mountain slopes beneath cliffs and outcrops, where they have formed from continuous rock-fell. Debris fans composed of coarse, bouldery alluvium are commonly found at the mouths of steep ravines and tributary streams where they join the main valley. Isolated landslide deposits occur on steep slopes throughout the basin, and colluvial deposits mantle many of the lower valley footslopes below timberline.

Much of the watershed lies above timberline in a high alpine environment. Snow avalanches, debris flows in steep ravines and tributaries, and rock fall are constant geologic hazards which affect many parts of the area.

Structural Geology

Structurally, the Animas headwaters lie in the Silverton Caldera of the western San Juan Volcanic Depression. Mineral Creek and the Animas River run in valleys roughly defined by the arcuate ring-fault structure bordering the margin of the caldera. Other prominent structural features include the Eureka Graben, which defines a prominent down-dropped area within the northern part of the caldera, and several associated zones of antithetic faults tangential to or radiating out from the margin of the caldera. Much of the upper headwaters area north of Animas Forks lies in one of these zones of complex fault systems which strike northeast, tangential to the northern margin of the Silverton Caldera. These fault swarms continue northeasterly into the adjacent Lake City Caldera structure. The Eureka Graben and associated northeast-striking faults are believed to have formed as the domed-up caldera rocks above active magma chambers relaxed and sagged back during periods of volcanic quiescence and magma retreat. During the numerous pulses of volcanic activity through the late Tertiary, faults bounding the graben and tangential to the caldera were repeatedly reactivated. Today, the Eureka Graben is a boot-shaped structure bounded by a series of major, steeply dipping mineralized faults.

The Red Mountain Block is located on the northwestern edge of the Animas drainage basin west of the Eureka Graben, noith of Gladstone. Rocks in the roughly circular block are down-dropped relative to the surrounding strata, and have been intensely solfatized and pyritized by hot sulphurous gases and solutions moving upward along and within this structure. All three of the “Red Mountains” lie within this roughly circular down-dropped block.

Stocks and dikes intruded into the margins of the caldera along the ring-fault zones may have an influence on groundwater flow systems associated with the streams running in the ring-fault valleys. Hie margins of the intrusives appear to be potentially conducive to groundwater flow, where the rock is often finely veined and shattered, resulting in a higher degree of alteration, and an almost continuous mesh-like pattern of macro-fractures which extend into the rock for several to tens of meters. Increased flow of meteoric ground and/ or geothermal waters along the shattered margins of the intrusives may in part account for the higher degree of alteration of the intrusive and enclosing country rock commonly seen along the contacts ofthese bodies, hi at least two cases, increased groundwater discharge and metals loading to the streams have been found to correlate to the positions of intrusive bodies outcropping in the stream valley.

Hydrothermal Alteration

All the volcanic rocks in the San Juan Volcanic Depression were extensively propylitized and 11 altered on a regional scale, prior to sulfide ore deposition. “Propylitic” alteration is a term used to describe a particular type of mineralogic and chemical change that occurs by circulation of aqueous hydrothermal solutions through the original volcanic rock mass, Propylitic alteration adds carbon dioxide and water to the rock mass, resulting in mineralogical changes to the rocks. This alteration is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. Propylitic alteration has resulted in a dull green or greenish gray color to virtually all of the volcanic rocks in the Animas watershed. Regional solfataric alteration occurs in the Animas watershed, and can be correlated directly with observed stream water quality. Rocks near the structural margin of the caldera and around volcanic breccia pipes have been highly altered by gaseous solfotaric and hydrothermal processes. “Solfataric” processes have subjected the rock to attack and leaching by hot sulphurous gases and solutions moving upward along the structural margin of the Silverton Caldera and Red Mountain block. These hydrothermal processes have leached most of the base minerals from the rocks, while introducing such large amounts of sulphur that this type of solfatarically-altered terrain is readily distinguished from the surrounding regional propylitic alteration. Volcanic flows in the Red Mountain area forming the northwestern part of the caldera were so strongly altered and leached that little remains except silica, kaolinite, and sulfate and sulfide alteration products, Virtually all potential buffering minerals in the country rock have been leached away, leaving the quartz-allunite-pyrite alteration assemblage characteristic of the Red Mountain District. Bleaching of the rocks and subsequent surficial oxidation of the solfataric pyrite through geologic time has resulted in the brilliant red, orange, and yellow staining which characterizes the “Red Mountains”. Much of the fresh country rock exposed in the banks of Mineral Creek from the South Fork to the Middle Fork, and in the area from Chattanooga to the confluence of Bighorn Gulch, is intensely pyritized. Fresh pyrite and secondary sulfosalts encrust the natural outcrops in these areas. The same is true for most of the gulches draining the west side of Cement Creek, from Gladstone to Silverton. Numerous acid springs and seeps occur all along the creeks in these solfatarically altered zones, and have been shown to be a source of metals to the streams draining these highly altered areas.

On the eastern and southern caldera margins, solfatric processes do not seem to have been as prevalent. There are only a few scattered areas of naturally pyritized country rock in the headwaters of the upper Animas, or streams draining the eastern half of the caldera, as compared to Cement and Mineral Creek watersheds. Base minerals remain in the rock, and the greater abundance of carbonate minerals in the veins and country rock provide better buffering capacity to the hydrologic system in this part of the basin. Water quality in the gulches draining this eastern area is generally very good. Wall rock adjacent to mineralized veins has been subjected to more intense but localized alteration processes. Wall rock alteration occurred episodically as the veins were subjected to successive phases of mineralization from solutions having often very different composition, and therefore varies with the individual vein deposit.

Manganese minerals are characteristic of alteration in wall rock along many of the major fault- fracture veins. Manganese from mineralizing solutions moving through the fissure veins has penetrated the wall rocks, leaving rhodonite and rhodocrosite alterations. Where weathered on the surface, these manganese-altered rocks often are conspicuous due to the characteristic black 12 staining of manganese oxides (pyrolusite, psilomelane).

Extensive silicification and deposition of quartz along the veins occurs in many areas of the watershed. Silicification has resulted in spectacular, resistant, outcropping veins which can be traced by eye for thousands of feet across the surface in the California Gulch and Burrows Gulch areas. Often the silcification has resulted in stock-works of quartz veinlets running in the veins and wall rock of larger fracture systems.

Carbonate minerals such as calcite and dolomite are also found in some veins and in the wall rock on the eastern margin of the watershed. The higher incidence of carbonate mineralization and alteration are believed to in part account for the improved buffering and subsequent better quality of ground and surface waters draining this part of the basin.

(END of OVERVIEW PIECE, be sure to Include References at end of this document) CEM ENT CREEK SUB-BASIN

The Cement Creek watershed lies within the Silverton Caldera, a regionally prominent Tertiary- aged volcanic center within the larger San Juan Volcanic Depression.

Stratigraphy

The Tertiary-age Silverton Volcanic Group underlies the Cement Creek area. Included in the Silverton Volcanic Group are the Bums Formation and overlying Henson Formation. A stratigraphic column of the units in the area is shown on Figure 2. The Burns Formation consists dominantly of medium to dark brown and black, thick, massive rhyodacite and quartz latite flows and flow breccias. This sequence of rocks has been divided into several units, including a lower flow-layered amphibole-bearing member, a pebble-tuff unit, and an upper, massive pyroxene- bearing member (Burbank and Luedke, 1969). The overlying Henson Formation consists of dark, dense, coarse-grained porphyritic and amygdaloidal flows and flow breccias, and fine-grained sandy tuffs of andesitic and rhyodacitic composition. Although there are many interesting local variations in texture, volcanic structures, and mineralogy of die dark volcanic flows in the area, they are generally too localized and discontinuous to map, and these variations are not important for this investigation.

Structural Geology Structurally, the Cement Creek basin lies in the northern part of the Silverton Caldera. The basin is affected by both the ring-fault structure defining the western edge of the caldera and the Eureka Graben, which defines the down-dropped area within the caldera. The Eureka Graben is believed to have formed as the domed-up caldera rocks above active magma chambers relaxed and sagged back during periods of volcanic quiescence and magma retreat. During the various resurgences in volcanic activity through the late Tertiary, the faults bounding the graben were repeatedly reactivated. Today, the Eureka Graben is a boot-shaped graben bounded by a series of major, steeply dipping mineralized faults. (Burbank and Luedke, 1969)

Figure 2 is a map showing the structural geology of the area. The Cement Creek basin is situated inside the caldera, several miles east of the bordering ring-fault structure and at the southwest end of the Eureka Graben.

Hydrothermal Alteration

All the volcanic rocks in the San Juan Volcanic Depression were extensively propylitized and altered on a regional scale, prior to ore deposition. “Propylitic alteration is a term used to describe a particular type of mineralogic and chemical changes which occurred by circulation of aqueous hydrothermal solutions through the original volcanic rock mass. The addition of carbon dioxide and water to the rock mass resulted in mineralogical changes to the rocks. Propylitic alteration here is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. Propylitic alteration has resulted in a dull green or greenish gray color to virtually all of the Bums Formation rocks.

Rocks near the structural margin of the caldera and around volcanic breccia pipes have been highly altered by solfataric and hydrothermal processes. “Solfataric” processes have subjected the rock to attack and leaching by hot sulphurous gases and solutions moving upwards along the structural margin of the Silverton Caldera and Red Mountain graben. These hydrothermal processes have leached and “stewed” most of the base minerals from the rocks, while introducing such large amounts of sulphur that this type of solfatarically-altered terrain is readily distinguished from the surrounding regional propylitic alteration. Volcanic flows within the Red Mountain block forming the northwestern edge of the Cement Creek basin were so strongly altered and leached that little remains except silica, kaolinite, and sulfate and sulfide alteration products. Virtually all potential buffering minerals in the country rock have been leached away, leaving the quartz-allunite-pyrite alteration assemblage characteristic of the Red Mountain District. Bleaching of the rocks and subsequent surficial oxidation of the solfataric pyrite through geologic time has resulted in the brilliant red, orange, and yellow staining which characterizes the “Red” Mountains.

Wall rock adjacent to the vein deposits has been subjected to more intense but localized alteration processes. Wall rock alteration occurred episodically as the veins were reopened and subjected to successive phases of mineralization from solutions having often very different composition.

Manganese minerals are characteristic of alteration in the wall rocks of the major fault-fracture veins. Manganese from mineralizing solutions moving through the fissure veins has penetrated the wall rocks, leaving rhodonite and rhodocrosite alterations. Where weathered on the surface, these manganese-altered rocks often are conspicuous due to the characteristic black staining of manganese oxides (pyrolusite, psilomelane).

Surficial Geology

Many of the slopes in the Cement Creek basin are steep and prone to snow avalanches, rockfalls, and debris flows. Above timberline, rock outcrops dominate the landscape and soils are thin to patchy tundra varieties. Near the ridges bordering the basin are several active rock glaciers. The lower valley walls and valley floor are extensively mantled by talus deposits. Alluvial deposits are present on the valley floor in isolated patches.

Ross Basin Watershed

Bedrock Geology

The Ross Basin area is situated near the center of the Silverton Caldera. Bedrock consists dominantly of the massive rhyodacite and quartz latite flows and flow breccias of the Silverton Group Bums Formation. All of the members of the Bums Formation are present in the Ross Basin watershed. The overlying Henson Formation, consisting of porphyritic and amygdaloidal flows and flow breccias, and fine-grained sandy tuffs, crops out on the upper slopes of Bonita Peak and Sunnyside Saddle. (Burbank and Luedke, 1969)

Structural Geology

Structurally, Ross Basin lies in the north-central part of the Silverton Caldera, within the major, steeply dipping mineralized faults of the Eureka Graben (Burbank and Luedke, 1969). Figure 2 shows the structural geology of the area. The Ross Basin Fault forms the top of the boot-shaped graben’s “toe”. It trends southeastward from just north of the main Cement Creek valley, along the northern wall of Ross Basin, and continues through the Sunnyside Saddle into the Lake Emma basin. Near Lake Emma, it makes an almost right-angled junction with the northeast-trending Sunnyside Fault. Dips on the Ross Basin Fault are from 75° to 80° south, with the south block (hanging wall), being downthrown. Displacement is greatest at the junction with the Sunnyside fault, and decreases westward through Ross Basin. A second major parallel and curving strand of the Ross Basin Fault structure splits off south into the hanging wall in lower Ross Basin. Heavily mineralized and persistent over several thousand ft., it is known as the Grand Mogul Vein. It runs along the foot of the north valley wall just above the floor of the basin. This vein has been extensively mined in both upper and lower Ross Basin, and was stoped to the surface in several locations. Numerous mineralized fractures (veins) branch off and cut nearly perpendicularly across the two main southeast-trending fault strands. These north-northeast trending veins form a series of repeating narrow fault blocks eastward along the slopes of Hurricane Peak, continuing northwards into the upper part of Poughkeepsie Gulch, and through the Hurricane Pass area in the high north branch of Ross Basin near the Queen Anne Mine.

Hydrothermal Alteration All the volcanic rocks in the Ross Basin area, and indeed the entire San Juan Caldera region, were extensively propylitized and altered on a regional scale, prior to ore deposition, Propylitic alteration here is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. It has resulted in a dull green or greenish gray color to virtually all of the Bums Formation rocks. Wall rock adjacent to the vein deposits has been subjected to more intense but localized alteration processes. Quartz, sericite, and pyrite are common mineralogical products of wall rock alteration associated with the siliceous sulfide veins in the Ross Basin area.

Manganese minerals, such as rhodonite and rhodocrosite, are also characteristic of alteration in wall rock of the major fault-fracture veins. Where weathered on the surface, these manganese- altered rocks often are conspicuous due to the characteristic black staining of manganese oxides (pyrolusite, psilomelane).

O re M ineralization

Ore mineralization in the Ross Basin area occurs as siliceous sulphide veins associated with the extensive system of open fissures created along the major Eureka Graben structure. Although the mineralized faults and fissures can often be traced for hundreds of ft. to several miles, economic ore deposits (“ore shoots”), occur on a much more restricted basis due to localized influences of structure and mineralizing solutions. Many of the most productive ore shoots of the district are found within the Ross Basin and Sunnyside fault veins.

The most common sulfide minerals of the veins are pyrite, chalcopyrite, sphalerite, galena, and tetrahedrite. Tennanite also occurs, and free gold is associated with localized shoots and in siliceous gangues, such as rhodonite (“pink”, as the miners called it). (Ransome, 1901). Gold has also been found associated with the base metal sulphides in some veins. Silver is associated with argentiferous tetrahedrite and sometimes with silver sulfosalts and sulfobismutites (Burbank and Luedke,1969). Gangue minerals associated with the veins in Ross Basin consist dominantly of quartz, rhodonite, rhodocrosite, calcite, fluorite, and minor barite. There is thus a better potential for buffering capacity associated with the veins of Ross Basin than in veins in Prospect Gulch-Georgia Gulch and upper Mineral Creek,

Sulphide minerals found on the mine dumps of the Grand Mogul vein workings and the main Mogul Mine dump included pyrite, galena, and sphalerite. There was abundant calcite, rhodonite, and quartz as well. The Grand Mogul vein is considered by some local workers to be one of the only veins in the district which might be successful as a lead-zinc mining operation,

Surficial Geology

Slopes around upper Ross Basin are steep, and prone to snow avalanches and rockfalls. Much of tli© lower valley walls and valley floor are mantled by talus deposits. There is also an active rock glacier near the upper basin headwall on the north slope of Bonita Peak, which is believed to have an ice core. As the basin is generally at and well above tree line, soils are thin to patchy tundra varieties, with rock outcrops dominating the landscape.

The avalanche danger in Ross Basin is high. Many avalanche chutes exist on both sides of the valley, and it is common to see huge piles of snow in the runout zones on the valley floor persist well into August of each year. It appears that past avalanches have damaged or destroyed all the structures which may have remained in the basin. Nothing is left standing, and wood and timber debris has been spread all along the valley floor.

Upper Cement Creek runs through extensive talus deposits in Ross Basin. There are only small isolated patches of true stream alluvium.

Cement Creek-Bonita Peak Watershed area

Bedrock Geology The Cement Creek-Bonita Peak area is situated near the center of the Silverton Caldera. Only the upper massive pyroxene-bearing member of the Silverton Group Bums Formation is present in the Cement Creek-Bonita Peak area. The upper slopes of Bonita Peak east and above the four sites are comprised of the overlying Henson Formation.

A highly mineralized volcanic breccia body lies just north of the Red & Bonita Mine and south of the Adams Mine on the east valley wall of Cement Creek. Exposures are poor due to overlying talus and colluvial deposits, however, the breccia body was reportedly exposed in mine workings (Burbank and Luedke, 1969). The country rock has been brecciated and highly pyritized within the pipe. Subsequent oxidation of this pyritized mass by groundwater is believed to be responsible for forming the unusual iron oxide deposits on the slopes and within the wetlands along Cement Creek near the Red & Bonita Mine.

Structural Geology

Structurally, the Cement Creek-Bonita Peak area lies in the north-central part of the Silverton Caldera, adjacent to the Eureka Graben (Burbank and Luedke, 1969). This boot-shaped graben is bounded by a series of major, steeply dipping mineralized faults which define and outline the down-dropped structure within the caldera complex, (Figure 2), as described in the geology

1 7 section at the beginning of this report.

The Bonita Fault forms the boot-shaped graben's "sole" on its southwest margin, and lies 2,500 ft. east of the Cement Creek sites, and 1,000 ft. east of the Lead Carbonate Mine. It trends northwest-southeast on a curving strike from the head of Gray Copper Gulch just north of the main Cement Creek valley, across Cement Creek near the Mogul Mine, and continues across the west shoulder of Bonita Peak just above the Lead Carbonate Mine. It terminates near the summit of Emery Peak 3,500 ft. northeast of the Black Hawk workings, where it forms a nearly right- angled junction with the northeast-trending Toltec Fault. Dips on the Bonita Fault are from 75° to 80° NE, widi the northeast block (hanging wall), being downthrown.

The upper Bums Formation southwest of the Bonita Fault has been tilted southwestward, and is broken by numerous small faults and sheeted zones in parallel and diagonal orientation to the main Bonita structure. These types of mineralized fractures have been developed by mines in the area of upper Cement Creek, and in the Middle Fork area.

The Lead Carbonate vein lies in the footwall of the Bonita block (Figure 2), and trends northeastward, nearly perpendicular to the northwest strike of the Bonita Fault. Repeated downward movement of the Bonita block in the hanging wall is believed to have caused dilation of this major fracture, forming the structure for the Lead Carbonate ore body (Burbank, 1951).

Hydrothermal Alteration All the volcanic rocks in the Cement Creek-Bonita Peak area were extensively propylitized and altered on a regional scale, prior to ore deposition. In this area of the Silverton Caldera, propylitic alteration is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. Propylitic alteration has resulted in a dull green or greenish gray color to virtually all of the Bums Formation rocks.

Wall rock adjacent to the vein deposits has been subjected to more intense but localized alteration processes. Quartz, sericite, and pyrite are common mineralogical products of wall rock alteration associated with the siliceous sulfide veins in the Cement Creek-Bonita Peak area .

Manganese minerals, such as rhodonite and rhodocrosite, are also characteristic of alteration in wall rock of the major fault-fracture veins. Where weathered on the surface, these manganese- altered rocks often are conspicuous due to the characteristic black staining of manganese oxides (pyrolusite, psilomelane).

Ore Mineralization Ore mineralization in the Cement Creek-Bonita Peak area occurs as quartz-pyrite veins associated with the system of open fissures created southwest of the Bonita block of the major Eureka Graben structure. Although the mineralized faults and fissures can often be traced for hundreds to thousands of ft., economic ore deposits or ‘ore shoots’ occur on a much more restricted basis due to localized influences of structure and mineralizing solutions. The most common sulfide minerals of the veins are pyrite, chalcopyrite, sphalerite, galena, and tetrahedrite. Tennanite also occurs, and free gold is associated with localized shoots, and in the siliceous gangue minerals, such as rhodonite. Gold has also been found associated with the base metal sulphides in some veins. Silver is associated with argentiferous tetrahedrite, and sometimes with silver sulfo salts and sulfobismuthites ( Burbank and Luedke,1969). The Adams Mine ores 18 reportedly contained enough hubnerite, a sulfide of tungsten, to be mined profitably for a short time.

Gangue minerals associated with the veins consist dominantly of quartz, rhodonite, rhodocrosite, calcite, fluorite, and minor barite. Not all the veins have the manganese gangues, as these are preferentially found in the major fault structures.

Surficial Geology

Upper Cement Creek Sites Cemen t Creek runs in a broad valley bordered by a nearly continuous apron of talus on both sides. The stream is braided in many sections, but has formed continuous alluvial deposits and low terraces through the area. There are some isolated ferricrete deposits, as well as extensive, boggy wetland areas developed on gentle colluvial slopes adjacent to the stream.

Slopes bordering Cement Creek are steep, but heavily timbered and generally outside of avalanche paths. The exception is a steep ravine coming down the west slope of Bonita Peak adjacent to the Adams Mine. It is major avalanche track, and is also a source area for debris flows, which have formed a debris fan on the valley floor of Cement Creek.

SOUTH FORK CEMENT CREEK AREA

Location The “South Fork area” as used here includes two mines on the South Fork of Cement Creek one mile south of Gladstone. The South Fork area is just south of the previously described Cement Creek-Bonita Peak area, and much of the geologic setting is similar. Mine sites selected by DMG and ARSG for reclamation feasibility studies include the Big Colorado and Silver Ledge Mines. These sites are shown on Figures 3 and 6. The sites are situated on privately owned patented lode mining claims. Coordinates of each site are given in the individual site descriptions which follow below.

The South Fork of Cement Creek sites are characterized by rugged, steep, high alpine terrain just below timber line. Winters are long with snow depths averaging 440 inches. The summer growing season is short. Average annual precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (Sunnyside Gold Corporation, 1996).

Bedrock Geology

The South Fork area is situated near the center of the Silverton Caldera. Only the upper massive pyroxene-bearing member of the Silverton Group Bums Formation is present in the South Fork area. The summit of the 12,164 ft. unnamed peak above the Big Colorado Mine is comprised of the overlying Henson Formation, which strike east-west and dip 15 □ south in that area.

Structural Geology

Structurally, the South Fork area lies in the north-central part of the Silverton Caldera, in an area between two major structural elements. It is one mile east of the southwest margin of the Eureka Graben, defined here by the Bonita Fault, and 3 miles east of the ring-fault structure which defines the western margin of the caldera along Mineral Creek. Figure 2 shows these structures in relation to the South Fork area. (These structures have been described above in the geology section at the beginning of this report.)

Strikes and dips of planar flow structures in the upper Bums Formation in the South Fork area are varied over short distances. Dips range from 10Q DNW at the Big Colorado Mine, to 36QDSW at the Silver Ledge Mine. At the Silver Ledge Mine, the rocks have been broken by numerous small faults and sheeted zones, in roughly parallel and diagonal orientation to the main Bonita structure one mile east. At the Big Colorado Mine, several fractures and faults are oriented on a trend which extends westward into the Prospect Gulch fault structure, which forms the south margin of the Red Mountain block. These fractures were subsequently mineralized, and have been mined in the South Fork area.

Hydrothermal Alteration All the volcanic rocks in the South Fork area were extensively propylitized and altered on a regional scale, prior to ore deposition. In this area of the Silverton Caldera, propylitic alteration is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. Propylitic alteration has resulted in a dull green or greenish gray color to virtually all of the Bums Formation rocks.

Wall rock adjacent to the vein deposits has been subjected to more intense but localized alteration processes. Quartz, sericite, and pyrite are common mineralogical products of wall rock alteration associated with the siliceous sulfide veins in the South Fork area.

Ore Mineralization Ore mineralization in the South Fork area occurs in similar fashion as that previously described for the Cement Creek-Bonita Peak area. Numerous quartz-pyrite veins have been formed in the system of open fissures created southwest of the Bonita Fault block of the major Eureka Graben structure. Although the mineralized faults and fissures are generally less persistent in length here, probably because of greater distance from the graben structure, they can often be traced for hundreds of ft.. Economic ore deposits within the veins are also less frequent, occurring on a much more restricted basis than in areas more closely associated with the major fault structures farther north and east. The most common sulfide minerals of the veins are pyrite, chalcopyrite, sphalerite, galena, and tetrahedrite. Tennanite also occurs, and free gold is associated with localized shoots, and in the siliceous gangues, such as rhodonite, though these are much less common in veins of the South Fork area. Gold has also been found associated with the base metal sulphides in some veins. Silver is associated with argentiferous tetrahedrite.

Gangue minerals associated with the veins consist dominantly of quartz, rhodonite, rhodocrosite, calcite, fluorite, and minor barite. Not many of the veins in the South Fork area have the manganese gangues, as these are preferentially found in and near the major fault structures bounding the Eureka Graben.

Surficial Geology The South Fork of Cement Creek lies in a steep narrow valley bordered by a nearly continuous apron of talus and coalescing debris-flow fans. The stream is so choked and constantly overrun with talus and debris flow sediments that it does not form a true alluvial channel until nearly reaching Gladstone. Just below the Silver Ledge Mine on the east valley wall, a landslide deposit 20 has moved into the valley, deflecting the creek westward into talus deposits.

PROSPECT GULCH-GEORGIA GULCH AREA

Location The headwaters of Prospect Gulch begin 1 Vz miles west of Cement Creek, and drain the south slopes of Red Mountain No. 3. Elevations in the Prospect Gulch drainage range from 12,890 ft. on Red Mountain No. 3, to 10,360 ft. at the confluence with Cement Creek one mile southwest of Gladstone. Georgia Gulch has similar elevations and aspect, and lies south of Prospect Gulch below McMillan Peak.

Mine sites selected by DMG for reclamation feasibility studies include the Upper Prospect Gulch Adit, Galena Queen, Hercules, Lark, Henrietta, and Joe & Johns sites in Prospect Gulch, and the Kansas City Mines in Georgia Gulch. These sites are shown on Figures 4 and 7.

The area is characterized by rugged, steep, high alpine terrain at and above timber line. Winters are long with snow depths averaging 440 inches. The summer growing season is short. Average annual precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (Sunnyside Gold Corporation, 1996).

Geologic Setting

The regional geologic setting of the Cement Creek area is discussed at the beginning of this report. More specific information about the Prospect Gulch-Georgia Gulch area is included below.

Bedrock Geology

The Prospect Gulch-Georgia Gulch area is situated just inside the northwestern margin of the Silverton Caldera. Caldera rocks in the Upper Prospect Gulch-Georgia Gulch area consist dominantly of medium to dark brown and black, thick, massive rhyodacite and dacite flows and flow breccia of the Silverton Group Bums Formation, and rhyodacitic flows, breccias and tuffs of the overlying Henson Formation, which form the slopes and summit of Red Mountain No. 3 in the upper drainage basin.

Two late-stage intrusive quartz latite porphyry plugs lie northeast of the Hercules and Galena Queen Mines on the south upper slopes of Red Mountain No. 3. The intrusive plugs lie on and adjacent to the bounding fault of the down-dropped “Red Mountain Block”, (Burbank and Luedke, 1969), and are similar in structure and nature to the other numerous late-stage intrusive plug-type quartz latite bodies associated with the margin of the Silverton Caldera and Red Mountain block structure.

A highly mineralized volcanic breccia pipe lies beneath the Hercules and Galena Queen Mines. These volcanic breccia pipes are the hosts for rich silver sulphide ore deposits known in the Red Mountain Pass district. The pipe and several associated veins were developed by the Hercules and Galena Queen workings. The Henrietta workings also reportedly developed along a blind (not exposed at the surface) breccia pipe known as the “Surprise Chimney” (Steve Fiem, Personal Communication, 1994.) Structural Geology Structurally, the Prospect Gulch-Georgia Gulch area lies within the Silverton Caldera on its northwest margin, one mile east of the complex system of ring-fracture faults related to its subsidence, and adjacent to the south margin of the down-faulted Red Mountain block, as shown on Figure 2. Numerous mineralized faults (veins) in upper Prospect Gulch trend parallel or sub­ parallel to the main ring fault trend of N.220E. A curved fault forming the southern margin of the Red Mountain block runs along the north, side of Prospect Gulch, crossing below the main Prospect Gulch road just above the Lark Mine. Springs and boggy areas between the main road and access road to the Henrietta 7 appear to delineate a branch off this fault, which continues along the north bank of the creek to just below the Joe & Johns Mine. The main fault strikes N.50DW. along the north bank of the gulch above the Lark Mine, swinging to N.85 DW near the Lark Mine. The Lark Mine portal lies just south of the surface fault trace, and the adit probably cuts the fault within 300 ft. from the portal. This unmineralized fault separates down-dropped rocks of the highly-altered Henson formation to the north from less altered Bums formation rocks, Dips could not be measured, but the fault appeared to be near vertical to steeply dipping to the north. There may be from 600 to 1000 ft. of downward displacement on this fault, as reported by Burbank and Luedke (1969). This structure may extend eastward down the gulch, crossing Cement Creek into the South Fork/ Big Colorado area, as indicated by a series of mineralized fractures which follow this trend.

Within the down-dropped Red Mountain block, and truncated by the curved boundary fault described above, is a complex of small quartz latite intrusive bodies cut by a set of northwest trending veins. These veins were prospected by several adits and shallow pits. The veins appear to be a mineralized set of closely-spaced faults, each with a downward sense of movement to the northeast. An intrusive clastic dike, which strikes N.47 □ W. and dips 55 CUN., cuts across the easternmost vein in this series, near the portal of a prospect adit above the Lark Mine. This dike has sharp contacts, and consists of a fracture filling of rounded to angular fragments of country rock and Precambrian basement clasts. These clastic dikes are believed to have been formed by explosive, forceful injection of debris during the waning stages of volcanic activity (Burbank and Luedke, 1969).

Hydrothermal Alteration Due to the proximity of the caldera structural margin within a mile to the west of the Prospect Gulch-Georgia Gulch area, much of the rockmass here has been highly altered by solfataric and hydrothermal processes. Solfataric processes have subjected the rock to attack and leaching by hot sulphurous gases and solutions moving upwards along the structural margin of the Silverton Caldera and Red Mountain graben. These hydrothermal processes have leached and “stewed” most of the base minerals from the rocks, as described in the geology section in the beginning of this report. Volcanic flows within the Red Mountain block forming the northern side of Prospect Gulch were so strongly altered and leached that little remains except silica, kaolinite, and sulfate and sulfide alteration products. Virtually all potential buffering minerals in the country rock have been leached away.

Ore Mineralization Ore mineralization in the upper Prospect Gulch breccia pipes and associated veins is typical of 22 the Red Mountain Pass District one mile to the west. These features can be considered as belonging to that district from an ore geology perspective. The pipes are reflective of the quartz- alunite epithermal deposits. The most common ore minerals include enargite, pyrite, sphalerite, galena, bomite, chalcopyrite, proustite, pyargerite, stromeyerite, covellite, and chalcocite (Burbank, 1951). Sulphide minerals found on the mine dumps of the Galena Queen/ Hercules and Henrietta Mines include pyrite, enargite, covellite, and chalcopyrite. The deposits were mined in veins, breccia pipes, and as disseminations in wall rock, intensely altered to silica, alunite, and clays.

Gangue minerals associated with the chimney sulphides consist dominantly of barite, fluorite, and the products of rock alteration, namely clays, quartz, and heavily pyritized wall rock. Virtually all potential buffering minerals have been leached away.

The Lark, Joe & Johns, and Kansas City Mines developed vein deposits within somewhat different mineralization than found in the chimney/ breccia pipe deposits. Vein ores consist of pyrite, chalcopyrite, sphalerite, and galena, sometimes with tetrahedrite and tennanite. Silver was associated with argentiferous tetrahedrite, and less commonly with silver sulfo salts. Free gold occurred in shoots scattered in siliceous gangues, or associated with the base metal ore minerals. (Burbank and Luedke, 1964)

Gangue minerals associated with veins in the area normally include quartz, rhodonite, rhodochrosite, calcite, fluorite, and barite. There is generally more potential for the presence of buffering minerals in vein deposits, but because the Prospect Gulch-Georgia Gulch area has been so heavily altered by solfataric processes near the margins of the caldera structure, the veins here are mineralogically similar to the chimney ores, and buffering minerals are often depleted. (Burbank and Luedke, 1964)

Surficial Geology

Slopes around upper Prospect Gulch-Georgia Gulch are steep, and prone to avalanches and debris flows. Several steep ravines between the Lark and Joe & Johns Mine sites have well-formed debris cones where they impinge on the main gulch. The upper slopes of Red Mountain No. 3 are mantled with thick aprons of scree and talus, which feed the source areas for the debris flow ravines. Much of the area around the Lark Mine is composed of colluvial debris transported down from the slopes of Red Mountain No. 3. Because this material is stained bright red and yellow, it resembles oxidized mine dump material. In actuality, it is a natural highly oxidized and leached deposit. Tests show this colluvial material to be so highly leached and oxidized through geologic time, that it is not a source of significant metals release. There is actually much less mine waste at the Lark Mine site than it appears, because of the naturally red-colored debris around the site. This gravelly, cobbly debris could be a source for fill or construction materials, though it would not make suitable capping material unless heavily amended for vegetation.

The avalanche danger in Prospect Gulch and Georgia Gulch is high to moderate. Several avalanche chutes exist on the south side of Prospect Gulch in the area of the Henrietta Mine. It appears that past avalanches have damaged or destroyed structures on the Henrietta 7 dump, and also at the Henrietta 10 dump. Most, if not all, the slopes above timberline in the upper basin are subject to avalanches in the winter, as are the debris flow ravines near the Lark and Joe & Johns Mine sites.

Slopes below McMillan Peak in Georgia Gulch at the Kansas City Mines are extreme avalanche hazard areas. No structures remain standing, and avalanches often run all the way down Georgia 23 Gulch to Cement Creek. Access to the Kansas City Mines is usually blocked well into mid- August by the melting remains of snow slides in the upper part of the gulch.

Extensive boggy, colluvial deposits exist around the Galena Queen/ Hercules site where the basin slopes are less steep, and the gulch widens out into a cirque-like basin. These deposits are characterized by thick, black soils developed on fine to coarse gravelly and cobbly colluvial materials. Colluvial and alluvial soils exposed along some of the upper slopes and along first order streams in the upper ’’cirque” basin have locally been cemented with iron oxide, forming ferricrete deposits.

Thin, patchy alluvial gravels are present along Prospect Gulch, but are generally just a discontinuous veneer on bedrock.

LOWER CEMENT CREEK AREA

Location The Lower Cement Creek area as used here includes several sites along the main stem of Cement Creek between Gladstone and Silverton. Mine sites along Lower Cement Creek selected by DMG and ARSG for reclamation feasibility studies include the Galty Boy, Margaret Mine, Mammoth Tunnel, BLM Adit, Anglo Saxon and Gold Hub Mines. The locations of these mines are shown on Figures 5 and 8. These sites are situated on privately owned patented lode mining claims. Coordinates of each site are given in the individual site descriptions.

The area is characterized by rugged, steep, high alpine terrain below timberline. Winters are long with snow depths averaging 440 inches. The summer growing season is short. Average annual precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (Sunnyside Gold Corporation, 1996).

Geologic Setting The regional geologic setting of the Cement Creek area is discussed at the beginning of this report. More specific information about the Lower Cement Creek area is included below.

Bedrock Geology The Lower Cement Creek area is situated 2'/2 miles east of the western margin of the Silverton Caldera. Caldera rocks in the Lower Cement Creek area consist dominantly of medium to dark, brown and black, thick, massive rhyodacite and dacite flows and flow breccia of the Silverton Group Bums Formation, and rhyodacitic flows, breccias and tuffs of the overlying Henson Formation, which form the slopes and summits of some of the higher peaks above the valley.

Structural Geology Structurally, the Lower Cement Creek area lies within the Silverton Caldera. The area parallels Mineral Creek, 2 Vz miles to the west, which marks the zone of a complex system of ring-fracture faults related to caldera subsidence. Widely scattered mineralized stringers and faults (veins) in the Lower Cement Creek area trend parallel or sub-parallel to the main ring fault trend of N.22QE. Because the area is south of the complex structure and fracture systems associated with the Eureka Graben, and several miles west of the caldera margin, there are far fewer principal veins and mineralized structures, which limited economic mining activities.

Hydrothermal Alteration All the volcanic rocks in the Lower Cement Creek area were extensively propylitized and altered 24 on a regional scale, prior to ore deposition. In this area of the Silverton Caldera, propylitic alteration is typified by the formation and addition of chlorite, calcite, and clays in weakly altered rocks, to epidote, albite, and chlorite in the stronger phases. Propylitic alteration has resulted in a dull green or greenish gray color to virtually alt of the Bums Formation rocks in the Lower Cement Creek area.

Due to the proximity of the caldera structural margin to the west of Cement Creek, many local areas of the rockmass in the upper headwaters of tributary streams draining the west side of the valley have been highly altered by solfataric and hydrothermal processes. Solfataric processes have subjected the rock to attack and leaching by hot sulphurous gases and solutions moving upwards along the structural margin of the Silverton Caldera. These hydrothermal processes have leached and “stewed” most of the base minerals from the rocks. Volcanic flows in the Ohio Peak - Anvil Mountain area on the northern side of Prospect Gulch were so strongly altered and leached that little remains except silica, kaolinite, and sulfate and sulfide alteration products. Virtually all potential buffering minerals in the country rock have been leached away, leaving the quartz-allunite-pyrite alteration assemblage characteristic of the Red Mountain District. Bleaching of the rocks and subsequent surficial oxidation of the solfataric pyrite through geologic time has resulted in the brilliant red, orange, and yellow staining which characterizes these areas of alteration.

Ore Mineralization Economic ore mineralization in the Lower Cement Creek area veins is typically weak, compared to other areas farther north and northeast in the Cement Creek watershed. The veins in solfatarically altered areas are reflective of the quartz-alunite epithermal deposits. The most common ore minerals include enargite, pyrite, sphalerite, galena, bomite, chalcopyrite, proustite, pyargerite, stromeyerite, covellite, and chalcocite (Burbank, 1951). Sulphide minerals found on the mine dumps of the Anglo Saxon include pyrite, enargite, covellite, and chalcopyrite. The deposits were mined in veins, and as disseminations in wail rock, intensely altered to silica, alunite, and clays. Gangue minerals associated with veins in solfatarically-altered areas consist dominantly of barite, fluorite, and the products of rock alteration, namely clays, quartz, and heavily pyritized wall rock. Virtually all potential buffering minerals have been leached away.

Vein ores in Lower Cement Creek area in non-solfatized rock consist of pyrite, chalcopyrite, sphalerite, and galena, sometimes with tetrahedrite and tennanite. Occasional silver was associated with argentiferous tetrahedrite, and less commonly with silver sulfo salts. Very rare free gold occurred in isolated shoots scattered in siliceous gangues, or associated with the base metal ore minerals.

Gangue minerals associated with veins in the Lower Cement Creek area normally include quartz, rhodonite, rhodochrosite, calcite, fluorite, and barite. There is generally more potential for the presence of buffering minerals in vein deposits which are not associated with solfatized rocks. Solfataric processes near the western margins of the lower Cement Creek valley watershed have depleted base mineral constituents in the country rocks, and buffering minerals are depleted.

Surficial Geology Slopes around Lower Cement Creek are steep, and prone to avalanches and debris flows. Almost all the steep ravines between Gladstone and Silverton have well-formed debris cones and fans where they impinge on Cement Creek. The upper slopes of Ohio and Storm Peaks are mantled with thick aprons of scree and talus, which act as source areas for debris flows moving down the 25 many steep gulches and ravines which empty into Cement Creek, Much of this natural talus and slope debris material is stained bright red and yellow, resembling oxidized mine dump material. Tests show most of this colluvial material to be so highly leached and oxidized through geologic time, that it is not a source of significant metals releases.

The avalanche danger in Lower Cement Creek is high to moderate. Numerous avalanche chutes exist on both the east and west sides of the creek almost all the way down to Silverton. Snowslides often run all the way down to Cement Creek in several areas, though they are more prevalent in the upper parts of the tributaries above the valley.

Extensive boggy, colluvial and landslide deposits exist in the upper reaches of Porcupine and Ohio gulches below Ohio Peak. These deposits are characterized by thick, black soils developed on fine to coarse gravelly and cobbly and bouldery colluvial materials. Colluvial and alluvial soils exposed along some of the upper slopes and along first order streams in the upper tributary gulches have locally been cemented with iron oxide, forming ferricrete deposits, as have many of the terrace gravels and colluvial deposits along Cement Creek.

Alluvial gravels are present along Cement Creek. Ferricrete deposits have resulted from iron-rich groundwater redepositing hematite and other iron compounds in the interstitial spaces of alluvial and terrace gravels. The “cemented” nature of gravel and colluvium outcrops along the creek gave rise to its name.

ANIMAS RIVER HEADWATERS AND BURROWS CREEK

Location The headwaters of the Animas River begin near Engineer Pass approximately 2 miles north of Animas Forks. The headwaters originate as two streams, which join with Horseshoe Creek to form the Animas River. Elevations in the Animas headwaters area range from 13,708 ft. in Horseshoe Creek to 11,620 feet at the confluence with the Animas headwaters stream.

Burrows Creek is a tributary to the Animas River located approximately 1 mile north of Animas Forks. Burrows Creek drains the western and northern slopes of Houghton Mountain, entering the Animas 1,500 feet south of Horseshoe Creek. Elevations in Burrows Creek watershed range from 13,052 ft. on Houghton Mountain to 11,600 feet at the confluence with the Animas River.

Immediately below the steep headwaters of Burrows Gulch is a trans-basin diversion ditch. During low-flow sampling, the diversion was partially breached. A portion of the stream flow was diverted to the west, but the majority was continuing through Burrows Gulch in the historic channel. During the high-flow sampling, it was observed that the diversion ditch had been repaired, and virtually all the drainage from the headwaters was diverted.

The area is characterized by rugged, steep, high alpine terrain well above timberline. Winters are long with snow depths averaging 440 inches, and the summer growing season is short. Average total precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (SGC data).

Mine sites in this area selected by DMG and ARSG for reclamation feasibility studies include the Lucky Jack Mine, an unknown mine above Denver Lake, the Red Cloud and Boston mine complex, London Mine, Early Bird crosscut, Ben Butler mine, Prairie claim, and several unknown prospects on the footslopes of Houghton Mountain. These sites are shown on Figures 3 26 and 4. The mines are situated on privately owned patented mining claims. Coordinates of each site are given in the individual site descriptions, which follow below.

Geologic Setting The Animas River Headwaters and Burrows Creek area lie on the northern margin of the Silverton Caldera, in a complex zone of northeast- striking fissure veins (Figure 2). Bums Formation dacite and rhyodacite volcanic flow rocks outcrop at the Lucky Jack area and in Burrows Gulch west of Denver Hill. A younger system of unmineralized northeast-striking faults crosses Burrows Gulch between Denver Hill and the northern slopes of Houghton Mountain, just east of the London Mine. These faults lie along the contact of the Bums rocks and underlying Eureka Tuff member, which outcrops in lower Burrows Creek, and the Animas valley below Horseshoe Creek. The faults bound the margins of a younger intrusive body of rhyolite, which forms Denver Hill and the northern slopes of Houghton Mountain. An east-west striking, unmineralized younger fault intersecting the northeast-striking faults is postulated to underlie the Burrows Creek valley floor. The younger intrusive rhyolite body has fractured and partly altered the country rock enclosing it. In many places it is conspicuously flow-laminated and banded, and contains some very porous layers. Some outcrops on Houghton Mountain were observed to be solfatarically altered. The rhyolite weathers to a fine, platy, scree-sized talus, which blankets much of the north slopes of Houghton Mountain and Denver Hill. This intrusive body and its associated faults may create a preferential flow system for groundwater draining through the mines and mineralized ground on the northern and western slopes of Houghton Mountain (see zinc discussion on pg. 21).

A prominently visible fault strikes northeast from the summit of Houghton Mountain, crossing lower Burrows Creek just above its confluence with the Animas. This mineralized structure, named the Denver Fault, continues across the Animas headwaters stream and Horsehoe Creek, crossing into Hurricane Basin through Denver Pass. In the pass, it offsets Bums Formation dacite flows against the older Eureka Tuff. The fault has a normal sense of movement, dips steeply north, and is marked by numerous prospect pits and adits.

Mineralized veins mined in this area strike northeast, tangential to the northern margin of the caldera structure. All the prominent mineralized structures continue northeasterly across Seigal Mountain and into the Henson Creek watershed. The veins are vertical or steeply southeast dipping, with normal sense of movement downward toward the southeast.

For much of its length, the headwaters of Burrows Creek near the Red Cloud Mine flows directly in a mineralized fault system. Some of the metals in the headwaters can probably be attributed to this complex vein system, Resistant outcropping ribs of white quartz along these vein structures have channeled the head waters of Burrows Creek into its present position. The trans-basin diversion collects the flow from the headwaters above the junction of the vein and the valley bottom. Where the fault-vein system crosses the valley bottom, there are numerous seeps and springs. It is likely that groundwater flowing in and along this structure is the source of most of the metals measured at sampling site BG-2 during the high-flow sampling, and is the principle source of the increase in loading between sampling sites BG-1 and BG-2 during the low-flow sampling. A multitude of north to northwest striking veins occurs north of the Denver Fault through Denver 27 Hill and Denver Lake. Several of these veins were observed to intersect northeast-striking veins at nearly right angles. Numerous prospect pits and adits were developed to explore these veins, but none of the major workings in the area occur on them. The unknown prospect adjacent to Denver Lake appears to have explored a short northwest striking vein,

CALIFORNIA GULCH

Location The headwaters of California Gulch begin near California Pass approximately 3 miles west of Animas Forks. California Gulch joins the Animas River at Animas Forks. The elevation range in the California Gulch watershed is 13,447 feet in the headwaters at Hurricane Peak to 11,150 feet at its confluence with the Animas River. Placer Gulch joins with California Gulch approximately 1 mile west of Animas Forks. Mine sites in this area selected by DMG and ARSG for reclamation feasibility studies include the Mountain Queen, Ida, Burrows, Vermillion, Vermillion Tunnel, Bagley Tunnel, And Columbus. These sites are shown on Figures 3 and 4. The mines are situated on privately owned patented mining claims. Coordinates of each site are given in the individual site descriptions, which follow below.

This area is characterized by a broad glaciated valley with the majority of the watershed above timberline. Winters are long with snow depths averaging 440 inches, and the summer growing season is short. Average total precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (SGC data).

Geologic Setting Bums Formation dacite and rhyodacite volcanic flow rocks outcrop in the upper part of the California Gulch watershed. Moving down valley, the older underlying Eureka Tuff outcrops in the floor and valley walls on down to Animas Forks. The contact between these two rock units is traceable on surface, where it climbs from 11,880 feet in the creek bottom up the north valley wall to the upper south shoulder of Houghton Mountain.

A long dike of younger intrusive quartz latite porphyry runs along the north valley wall of the gulch from the south summit of Tuttle Mountain to the southeast shoulder of Houghton Mountain. This younger dike follows a fracture system that offsets the Bums-Eureka contact along the floor of California Gulch. The dike joins with the larger intrusive porphyry mass forming the southeast shoulder of Houghton Mountain near the upper Columbus mine workings.

The younger intrusive porphyry body on Houghton Mountain has fractured and partly altered the country rock enclosing it. A prominent, broad zone of northwest trending mineralized fractures extends through the porphyry intrusive into the surrounding Bums and Eureka Tuff formations, probably reflecting the trend of the underlying ring-fault system here. This zone of deep-seated faulting was a fevorable site for solfataric hydrothermal alteration processes. Bums formation rocks capping the summit of Houghton Mountain are solfatarically altered, weathering to bright orange and red talus deposits, as is common in the Red Mountain district farther west

California Gulch lies on the northern margin of the Silverton Caldera, in a complex zone of fissure veins (Figure 2). There are roughly three vein sets: a dominant set of major northeast- striking fissures which run parallel to the northern margin of the Eureka graben throughout the area; a second set of dominant almost east-west trending fissures at the extreme head of the gulch near the Mountain Queen mine; a third north-northwest trending minor vein set in the Houghton 28 Mountain-Animas Forks area near the Columbus mine (Burbank and Luedke, 1969). This latter set may reflect the underlying ring-fault system on this margin of the caldera, which runs through the Animas Forks area.

Prominently visible silicified fissure veins of the first vein set crop out on the north valley wall of California Gulch. These veins are characterized by hard resistant white quartz ribs that can be traced through the saddle between Houghton and Tuttle Mountains, where they continue into the Burrows Creek watershed. The veins are vertical or steeply southeast dipping, with normal sense of movement downward toward the southeast. This principal vein system was the focus for prospecting and mining in California Gulch.

Surficial Geology Upper California Gulch is mantled with extensive unconsolidated surficial deposits. A large rock glacier spills down the steep slopes into the valley between Hurricane Peak and California Mountain. Extensive talus deposits cover the lower footslopes and southeast valley walls below California Mountain, and glacial and alluvial gravels and debris cover the valley floor near the head of the gulch. Talus and glacial deposits also cover much of the valley floor and the north slopes of Treasure Mountain near the Bagley Tunnel and Animas forks.

PLACER GULCH

Location

Placer Gulch is a tributary to California Gulch. The confluence of the two streams is located approximately 1 mile west of Animas Forks. Heavy metals in Placer Gulch principally come from four mining sources and un-quantified groimdwater inflow sources. Two of the mine sites, the Gold Prince, and Sunbank Property, have been partially reclaimed by the property owners. The remaining, known mining sources are the Silver Queen Mine and the Sound Democrat Mine. These sites are shown on Figures 2 and 3. The mines are situated on privately owned patented mining claims. Coordinates of each site are given in the individual site descriptions, which follow below. The Silver Queen and Sound Democrat mines can account for a maximum of 5,6% of the zinc and 35% of the manganese measured at the mouth of Placer Gulch at low-flow. During high-flow, the adit discharges can account for only 1.3% of the zinc and 2.8% of the manganese.

Only one stream station was monitored in Placer Gulch, It was decided not to monitor the upper portion of Placer Gulch because construction activities were occurring at the Gold Prince Mine during the low-flow sampling, and there was probably a larger than normal flush of metals from the construction site during the high-flow sampling.

Geologic Setting The principal geologic feature of interest in Placer Gulch is the Sunnyside Fault zone, which forms the northern margin of the Eureka Graben structure. This mineralized fault system extends northeast from the Sunnyside mine workings at Lake Emma, across the southeast shoulder of Hanson Peak into the head of Placer Gulch. The surface trace of the fault system runs along the valley floor of the upper gulch, then climbs the northwest slopes of Treasure Mountain. The fault offsets younger Bums Formation dacites and rhyodacites in the graben on the southeast side of the fault, downward against the underlying Eureka Tuff. The structure controls much of the fracturing style, and subsequently, position and orientation of the mineralized veins in Placer Gulch. The Eureka Tuff outcrops at the mouth of the gulch and along the lower northwest valley wall. Bums formation lava flows overly the tuff in the northwest valley wall, capping California Mountain. Rhyolite flows in the upper Bums formation cap parts of the high ridge between Placer Gulch and Parson and Picayune gulches, with lower Bums dacites and rhyodacite flows outcropping on the north slopes of Treasure mountain south of the Sunnyside fault.

A younger intrusive rhyolite body caps the west shoulder of California Mountain on the valley slopes above the Gold Prince Mine.

Placer Gulch lies across the northern margin of the Eureka Graben structure discussed previously; (Figure 2). There are two dominant vein sets in the gulch: 1)- a set of major northeast- striking fissures in or running parallel to the Sunnyside Fault system;2)- a north-northwest trending minor vein set running across the gulch nearly at right angles to the controlling Sunnyside structure, as exemplified by the Silver Queen vein. Prominently visible silicified fissure veins of the first group crop out along the upper valley floor. These veins are characterized by manganese-stained, resistant white quartz ribs that can be traced through the length of the gulch. This principal vein system was the focus for prospecting and mining at the head of Placer Gulch.

Surficial Geology Unconsolidated deposits cover less than 30% of the surface in Placer Gulch. A thick, extensive apron of talus mantles much of the upper valley walls and floor below the headwall of Placer Gulch in the vicinity of the Silver Queen and Sound Democrat workings, A large landslide on the northern slope of Treasure Mountain extends down onto the valley floor about midway up the gulch. A large deposit of glacial till and morainal debris remains near the middle of the valley floor below the Silver Queen and Sound Democrat mines, and glacial and alluvial gravels and debris cover the valley floor almost its entire length.

ANIMAS RIVER SITES. ( Animas Forks to Eureka)

Location The section of the main stem of the Upper Animas River below Animas Forks is discussed separately because, in general, water quality steadily improves downstream from Animas Forks. This section of stream starts at an elevation of 11,120 feet at Animas Forks and ends at an elevation of 9,840 feet. The major tributaries in this stream segment include Cinnamon Gulch, Grouse Gulch, Picayune Gulch, Bums Gulch and Niagara Gulch. The maximum elevation in the Upper Animas River is 13,860 feet at the headwaters of Bums Gulch. Adit discharges in this segment include the Golden Fleece, Treasure Mountain, Toltec, Silver Wing, Tom Moore, Senator, and an unknown mine between Grouse and Bums Gulch, These sites are shown on Figures 3 and 4. The mines are situated on privately owned patented mining claims. Coordinates of each site are given in the individual site descriptions, which follow below.

The Treasure Mountain Mine was not sampled because at the time, it was believed to have been sampled by CDPH&E. Later, no data could be located to document that the adit was ever sampled. This site should be sampled at least once to determine if there are any impacts to Picayune Gulch. Heavy metals concentrations in Picayune Gulch at the confluence with the Animas River are below chronic toxicity levels for aquatic life. 30 This area is characterized by rugged, steep, alpine and sub-alpine terrain. Much of the area is subject to destructive snow slides during the winter. Winters are long with snow depths averaging 440 inches, and the summer growing season is short. Average total precipitation for the past 3 years is 45 inches, 37 inches occurring as snowfall (SGC data).

Geologic Setting The canyon section of the upper Animas study area immediately above Eureka lies in the trough of the ring-fault structure which defines the Silverton Caldera. The ring structure is here expressed by the Animas Fault system, running along the west canyon wall from the mouth of the canyon at Eureka to a junction with the Cinnamon fault at Cinnamon Creek. The Animas Fault intersects the Toltec Fault near the mouth of Picayune Gulch. Numerous nearly east-west striking mineralized fault veins branch off the Animas Fault structure on into the east canyon wall. These veins in the Eureka Tuff were prospected and developed by several mines described in this section.

The Toltec Fault forms the southern margin of the Eureka Graben structure discussed previously. It continues across the Animas River and into Grouse Gulch, where it is known as the Anaconda Fault. The Toltec-Anaconda structure is apparently not heavily mineralized here, as none of the prospects or mines on it in the Animas canyon section produced much economic ore.

The lower canyon area near Eureka has the most extensive zones of solfataric hydrothermal alteration seen in the study area. The west canyon walls at Eureka are brightly stained red and orange, in similar fashion to hydrothermally altered rocks associated with the Red Mountain District farther west. Large zones of hydrothermally altered rock can be seen in both valley walls, and in Niagara Gulch. As discussed previously, these areas naturally have less buffering capacity, and probably contribute more background sulfate and metals than some of the other areas in this study.

EUREKA GULCH

Location Eureka Gulch is a “hanging” glacial side valley draining the north-central part of the Silverton Caldera. It enters the main Animas valley on its western side at Eureka.

Geologic Setting Upper Eureka Gulch lies in the north-central part of the Silverton Caldera, across the southern margin of the Eureka Graben, described above. The graben is bounded by the Suntiyside fault on the north, which joins the Ross Basin Fault near Lake Emma at the Sunnyside Mine in the upper headwaters of Eureka Gulch, The southern margin is bounded by the Toltec Fault, which cuts across Eureka Gulch at the Terry Tunnel site. Rhyolite flows within the graben are down-dropped relative to rock outside the graben. From above the Terry Tunnel, upper mountain slopes on the valley walls are composed of pyroxene andesite and the Henson Member of the Silverton Volcanics. South of the Terry Tunnel, and 31 along the lower valley slopes downstream of Lake Emma, the Bums Formation sequence of dacite and rhyodacite flows comprises the peaks and valley walls on down to Eureka. Hydrothermally altered outcrops of the underlying Eureka rhyolite ash-flow tuff can be seen in the mouth of the canyon of Eureka Gulch at the Eureka Mill site. This pyritized hydrothermal alteration zone continues northwards on the main Animas valley walls at Eureka, as indicated by the brilliant orange and red staining imparted to the outcropping rock, and talus deposits.

A breccia pipe or collapse structure lies on the eastern slopes of Bonita Peak in the vicinity of Lake Emma (Luedke and Burbank, 1987). This structure consists of a zone of silicified, brecciated rock enclosed by a series of localized concentric ring fractures, however, it is not as heavily mineralized as similar structures in the Prospect Gulch and Red Mountain areas. Mines and prospects in Eureka Gulch developed and explored the numerous mineralized structures related to the Eureka Graben, including the bounding Toltec and Sunnyside fault zones.

Surfical deposits mantle much of the valley and mountain slopes in Eureka Gulch. Talus, rock glaciers, glacial till, colluvium, and a large landslide deposit cover the steep side slopes in the upper basin above the Terry Tunnel. Extensive talus aprons and fans lie along the steep valley walls of the lower gulch, and alluvium has been deposited along the valley floor from the confluence of the South Fork to the canyon above Eureka.

MINNIE GULCH

Location Minnie Gulch is a large “hanging” side valley entering the main Animas River Valley on its east side, one mile below Eureka. Below the turnoff to the Kittimack Mine, Minnie gulch is steep" sided and v-shaped, while above this it is a broad, glacially carved open U-shaped basin on up to the continental divide. The area is characterized by rugged, steep, high alpine terrain, with the upper basin well above timberline.

Geologic Setting The geology of Minnie Gulch is quite uniform. The watershed is carved almost entirely in Bums Formation dacite and rhyodacite volcanic flow rocks. Exceptions are a small area where the underlying Eureka Tuff is exposed at the mouth of the gulch, and an isolated remnant of devitrified ash-flow tuff capping the drainage divide between Minnie and Cuba Gulches. All the rest of the rock exposed in the gulch belongs to the Bums formation, though several different hydrothermal alteration styles are present. There is some indication of moderate to locally strong solfataric alteration and pyritization of the Eureka Tuff and Bums Formation near the mouth of the gulch, along the margin of the ring-fault structure defining the caldera. Above the mouth of the gulch. Rock exposed in the upper basin is strongly propylitized.

Several large fault structures cut across the valley of Minnie Gulch, and are clearly visible in the high slopes above the stream valley. The longest and most prominent structure cuts across the lower gulch in the hydrothermally altered area, where it is marked by numerous prospects and workings. A swarm of weaker less persistent veins occurs in the middle and upper reaches of the gulch, and these too have been prospected. All these structures are parallel to the caldera marginal fault zone, and show a down-to-the-west sense of movement, reflective of caldera subsidence. Surficial Geology Upper Minnie Gulch is mantled with extensive unconsolidated surfical deposits. Talus and colluvium, as well as patchy glacial deposits cover parts of the valley floor. A large alluvial fan has formed at the confluence of Minnie Gulch and the main stem of the Animas, where the steep tributary canyon changes grade abruptly at the floor of the valley.

Geologic Hazards Avalanche chutes and runout zones are common on both sides of the gulch, extending well below timberline in the lower sections.

MAGGIE GULCH

Location Maggie Gulch is another of the U-shaped, strongly glaciated hanging tributary valleys which join the Animas valley on the east side Between Eureka and Howardsville. The mouth of Maggie gulch is at Middleton, Z2 mile south of Minnie Gulch.

Geologic Setting Maggie Gulch is similar in aspect and geology to Minine gulch, with a few exceptions. Bums formation rocks form the floor and slopes of the upper 2/3rds of the basin; the lower third through the narrow and steeper canyon section exposes the underlying Eureka Tuff ash-flow unit.

The principal geologic feature of interest in Maggie Gulch is the large and impressive granite- porphyry intrusive body cutting perpendicularly across the lower part of the valley. A broad, uniform scree slope marks the outcrop of this intrusive rock unit. The porphyry appears to have been intruded into weak, broken zones on the marginal structure at the edge of the collapsed caldera much later in geologic time. The intrusive weathers to a brightly oxidized, uniformly cobble-sized orange and red scree, which mantles the subcrop where the structure cuts across the gulch.

Surficial Geology

Unconsolidated deposits cover less than 20% of the surface in Maggie Gulch. Extensive aprons of talus mantles much of the upper valley walls and floor below the headwall of the gulch above the Little Maud site. An active debris-flow fan is forming at the mouth of a steep side gully on the north side of the valley just above the Little Maud mine. Small landslides and colluvial slips in die head of this ravine have flowed down and onto the valley floor, reaching the stream. Thin deposits of glacial till and morainal debris remain in scattered patches along the upper shoulders of the valley below the steep canyon section in the lower part of the valley.

CUNNINGHAM GULCH

Location

Cunningham Gulch is a broad, north-south glacially carved tributary valley which joins the main Animas valley at Howardsville. Geologic Setting Cunningham Gulch drains a much larger watershed than Minnie or Maggie Gulches. With a larger ice-source area and north-facing aspect, the Cunningham Gulch glacier cut the valley deeper, so that it joins the Animas very near the elevation of the main valley floor. Deeper down cutting has exposed the underlying Eureka Tuff along the base of the valley walls on both sides of the gulch, from just above the mouth to the Highland Mary Mine. Bums Formation dacite and rhyodacite volcanic flow rocks outcrop above the Eureka Tuff on the upper valley walls, and cap the high ridges on both sides of the gulch, accounting for an estimated 50% of the surface area of the watershed.

From near the Green Mountain Mine to the upper headwaters of the drainage, glacial ice has cut completely through the volcanic sequence, exposing underlying Precambrian and Paleozoic rocks. Amphibolite-gneiss and homblende-biotite-schist of the Precambrian Irving Formation outcrop below the Eureka Tuff in the base of the steep valley walls from near the mouth of Dives Basin, on to the top of the drainage divide at Highland Mary Lakes. All the lower portals of the Highland Mary are driven in Precambrian gneiss.

Just south of the Highland Mary Mine’s Bradley Level portal, a narrow graben structure cuts perpendicularly across the valley in the Precambrian section. Within this down-dropped, trough­ like structure, two isolated blocks of overlying Paleozoic carbonate sedimentary rocks have been preserved on each side of the creek. Limestone and Dolomite of the Leadville, Ouray, and Elbert Formations appear to have been quarried from within the graben above the Highland Mary Mill area. A large landslide composed of mostly of fractured blocks of Ouray limestone mantles the slopes above Mountaineer Creek here.

The younger intrusive porphyry body outcropping in Maggie Gulch continues through the northwest shoulder of Galena Mountain into Cunningham Gulch. It splits into two fingers cutting through the upper slopes on Galena Mountain, and can be traced all the way down to the valley floor, where it is exposed in the creek at the mouth of the gulch. A second larger intrusive body of quartz monzonite outcrops on the southwest valley wall of the Gulch opposite the Old Hundred Mine. It is marked by a conspicuous talus field, visibly different than surrounding Bums formation rock.

The intrusive body has fractured and partly altered the country rock enclosing it. It was intruded into broken, weaker zones along the ring-fault system bounding the southeastern margin of collapsed caldera structure. Hydrothermally altered zones in both the intrusive and the enclosing country rock are commonly seen along the contact. A prominent, broad zone of parallel northwest trending mineralized fractures extends southwestwards beyond the porphyry intrusive into the surrounding Bums and Eureka Tuff formations on the west side of the valley. These structures reflect the trend of the underlying ring-fault system here, and were prospected and mined at several sites in Cunningham Gulch and on the southern side of the main Animas valley.

Prominently visible mineralized fissure veins crop out on the slopes of Galena Mountain. These veins are characterized by alteration zones, and often resistant white quartz ribs and stringers which, in many places can be traced over Galena Mountain into Maggie Gulch. Workings in the Old Hundred, Gary Owen, and the mines in Rein Gulch developed these structures, as well as a series of prominent fault veins trending northwest-southeast, tangential to the Silverton Caldera structure. Dives Basin is a smaller, hanging cirque valley tributary to Cunningham Gulch on the southwest side of the valley. Workings in the upper basin were extensions on the Shenandoah-Dives Mayflower vein, extending through Little Giant Peak from Arrastra Basin. Several prominent andesite and latite dikes trend east-west across the south shoulder of Little Giant Peak into Dives Basin, and were prospected in numerous places in the upper cirque. An andesite dike is also intruded along the Precambrian-Eureka Rhyolite contact on the west valley wall of the gulch at Dives Basin. Stony Gulch and Rocky Gulch are two other hanging cirque valleys tributary to Cunningham Gulch on its eastern side. The lower parts of these gulches are steep and canyon-like, reflecting the hanging-nature of the tributary glaciers that cut them. In lower Stony Gulch, just above the confluence with Rock y Gulch, glacial scouring and subsequent stream downcuttmg have exposed the Eureka Tuff and underlying Precambrian gneiss and schist of the Irving formation. A series of prominent fault veins trending northwest-southeast, tangential to the Silverton Caldera structure, run from Galena Mountain southeastward into the Stony Gulch-Green Mountain area. These structures were prospected and developed in the Green Mountain, Buffalo Boy, and Gary Owen workings.

Surficial Geology Cunningham Gulch is floored with a relatively continuous outwash and alluvial gravel deposit. The gravels extend from just above the short, steeper canyon at the mouth, to the Highland Mary Mill, broken only by a short canyon section in the Eureka Rhyolite at the Pride of the West Mine. Extensive talus deposits cover many of the lower valley walls in Cunningham and its tributary gulches. Several rock glaciers exist in the cirques of Dives Basin, and Stony and Rocky Gulches.

ARRASTRA BASIN

Location Arrastra Basin is a hanging cirque valley tributary to the Animas River Valley on its south side, two miles above Silverton.

Detailed mapping has been conducted in Arrastra Basin (Burbank, 1933, Vames, 1963). Figure XX shows the geology of upper Arrastra and its tributaries, Little Giant and Woodchuck Basins. The lower part of the valley in the vicinity of the Mayflower/ Shenandoah-Dives Mine is cut in Eureka Tuff. Exposures are limited to the steep, nearly vertical valley walls, as the entire lower valley floor is mantled with a thick deposit of talus, scree, and glacial outwash. Below this thick deposit of unconsolidated debris, Bums formation rocks again crop out on the steep valley walls at the mouth of the basin. The upper basin is cut entirely in the Bums Formation dacite and rhyodacite volcanic flow rocks. In Arrastra Basin, the Bums has been subdivided further into a lower tuff-breccia member, a middle dacite flow and flow breccia, and an upper tuff member (Burbank, 1933). Capping Little Giant Peak is a pyroxene-andesite flow of the overlying Henson Formation. The lower tuff-breccia member is exposed in the lower slopes of the upper basin. It outcrops from above the Shenandoah-Dives Mine on both sides of the valley nearly to Silver Lake, and again on the south and west sides of Silver Lake on the lower slopes of Kendall Peak, through the Iowa Mine area. It also underlies the floor of the upper basin above Silver Lake. In Little Giant Basin, it outcrops across the lower valley floor from just above the Big Giant Mine to the mouth of the upper cirque basin, at 11,450 feet elevation.

The middle Bums dacite and rhyodacite flows and flow breccia unit outcrops over the rest of the basin slopes and ridges in Arrastra and Little Giant Basins. Round Mountain is made up of the flow-breccia unit, mapped separately on the basis of textural and structural differences. This middle breccia unit also outcrops on the lower footslope of the northwest shoulder of Little Giant Peak (Fig XX).

The upper tuff member of the Bums Formation is preserved only on the summits of Little Giant Peak and King Solomon Mountian. Here, the tuff member is exposed beneath a capping flow of pyroxene-andesite, believed to represent the lower part of the Henson Formation.

A broad zone of concentric northeast-southwest trending high-angle faults cuts peipendicularly across the lower basin, 3A mile down valley from the Shenandoah-Dives/ Mayflower Mine. Although covered by talus and outwash on the lower valley floor, the faults are clearly visible in the cliff walls surrounding the gulch. Individual fault strands dip steeply west, each having a normal sense of downward movement northwest-ward into the subsided Silverton Caldera, displacing the Eureka-Bums contact downwards across the fault zone. The overlying Burns rocks have been dropped into a position below the underlying Eureka Tuff, so that they outcrop on both sides of the gulch at its confluence with the Animas River. This complex fault zone represents a companion strand of the bounding ring-fault zone marking the structural margin of the caldera. It is parallel to and follows the main trace of the ring-fault, running under the valley floor of the Animas River at its confluence with Arrastra Gulch.

Two persistent dikes of younger intrusive andesite and quartz latite porphyry run dominantly east-west across Silver Lake basin in the upper cirque (Figure XX). These steeply dipping younger dikes can be traced on the surface for long distances, and persist into the subsurface, where they have been intersected at depth in mine workings. They follow a fracture orientation roughly parallel to the caldera margin. A third dike intersects the first two, running tangential to the caldera structure.

Cutting across these dikes is a series of younger northwest-trending mineralized fissure-vein systems extending somewhat radially from the ring-fault zone across Arrastra and Little Giant Basins (Figure XX). These vein structures hosted rich silver ore deposits exploited in the numerous mines in Arrastra, Little Giant, Dives, and Woodchuck Basins. Principal veins include the Gold Lake-Black Prince, Potomac, Shenandoah-Dives, Nevada-Silver Lake-Royal Tiger, Iowa, New York, Melville, and Titusville structures.

The veins are generally low-grade complex-sulfide type, and have been classed as upper mesothermal or epithermal deposits (Vames, 1963). Pyrite, galena, sphalerite, and chalcopyrite in a gangue of quartz and minor calcite are the most abundant vein minerals. Gold, argentiferous galena, and gray copper have accounted for most of the production values. Locally within the veins, tetrahedrite-tennanite has produced rich silver values. Visible free gold is very rare in this area, though it was reported in one specimen from the Royal Tiger (Ransome, 1901). Surficial Geology Upper Arrastra and Little Giant Basins are well above timberline, and almost devoid of surfical deposits. In places throughout the area, thin patchy aprons of talus and scree fill chutes and form aprons below cliffs. A wetland bog deposit of peat in alluvium and colluvium has formed on the flat basin floor at the inlet to Silver Lake, but it is thin, and discontinuous. Most of the upper watershed is composed of outcropping volcanic bedrock. In contrast, lower Arrastra Basin is completely choked with unconsolidated deposits. Thick, extensive blankets of talus, debris flows, and glacial outwash fill the lower basin below the Shenandoah-Dives Mine, to just above the short canyon section at the mouth of the gulch. Arrastra Creek flows subsurface beneath blocky talus and debris, from the base of the waterfalls at the cliffs near the Shenandoah-Dives/ Mayflower Mine, to the confluence of Little Giant creek. Patches of glacial till and morainal deposits are found on the upper side slopes of the lower valley, where they form hummocky, heavily forested benches above the creek floor. Avalanches and rockfall are a constant hazard throughout most of the watershed.

ANIMAS RIVER SITES

Location The Animas River follows a broad, U-shaped glacial valley from the mouth of the canyon below Silverton to Eureka townsite.

Geologic Setting From Eureka to Silverton, the Animas River valley is carved in volcanic flows of the Bums Formation. The valley follows the structural margin of the Silverton Caldera along the ring-fault structure, which separates the caldera from the rest of the volcanic field. On the north side of the valley, dacite and rhyodacite flows and breccias of the Bums Formation outcrop from the base of the valley wall to the summits of the highest ridges in the central caldera. On the south side, Eureka Tuff underlying the Bums rocks is exposed in the lower valley walls from Eureka to the mouth of Maggie Gulch. Most areas of the ring-fracture system are not economically mineralized (Vames, 1963). Narrow zones of iron and manganese oxides, with stringers of quartz are common on the ring faults, and other structures concentric to the caldera margin. Although many adits were driven to prospect these sturctures, base metal sulfides were only found in a few areas, and only in small amounts.

At Silverton, the wide, park-like valley occupied by the Animas River is underlain by a late to middle aged Tertiary intrusive stock. This hypabyssal intrusive poiphyritic quaitz-monzonite stock underlies the valley and both sides of the river from Silverton to the narrow mouth of the canyon at the Champion Mine. It also forms the northern slopes and summit of Sultan Mountain. Along the valley floor, it outcrops at the foot of Sultan Mountain from the Little Dora mine to the Champion mine, the northern half of Anvil Mountain, and along the west foot slope of Kendall Mountain from Silverton to the mouth of the Canyon at the Champion Mine. It is inferred to underlie the broad river valley at Silverton, beneath a relatively thick deposit of river alluvium.

This intrusive body is younger than the volcanic sequence of andesites and dacites- to-rhyodacites which occupy the main part of the Silverton Caldera. The rock was intruded into the southern margin of the caldera along the trend of ring-faults which run beneath the river valley, and which broadly 37 define and separate the caldera structure from the surrounding Paleozoic and pre-Cambrian section. It crosscuts and interfingers with the andesites, dacites, rhyodacites, and volcanic ash-flow tuffs of the caldera, as well as the Paleozoic sedimentary section on Sultan Mountain. Except in thin dikes and veins, the main body of the intrusive was not found in contact with pre-Cambrian rocks at the surface.

In outcrop, the quartz monzonite is a medium- to fine-grained porphyry, with a well-defined joint system. The rock weathers and breaks along sharp uniform joints, which intersect to create a characteristic blocky, angular talus on steep outcrops. The porphyry can often be traced on aerial photographs by the pervasive talus deposits it forms below most outcrops. Outcrops within the body of the unit are generally massive, having joint sets on a larger spacing. Rock exposed along the contacts of the stock are finely veined and shattered, resulting in a higher degree of weathering and an almost continuous mesh-like pattern of macro-fractures.

The brecciated, shattered nature of the intrusive contact in some areas, combined with crosscutting relations along associated veins and dikes, suggests a dilative, forceful intrusion of the stock into the margin of the Silverton Caldera, and adjacent Paleozoic section. This highly jointed structural fabric, intrusive post-caldera relationship of the stock, as well as its position between the caldera and the Precambrian section down stream, suggest the stock could have an important structural association to groundwater flow systems associated with the Animas River before it enters the canyon below Silverton..

A narrow section of lower Mississippian, upper Devonian and upper Cambrian sedimentary rock is exposed in a steeply plunging narrow band on the canyon walls of the Animas River in the vicinity of the Champion Mine. This thin remnant of the basal Paleozoic section is buried under the alluvial valley floor of the river where it crosses beneath the axis of the valley at the Champion Mine. The section continues in a narrow band along the south-western slopes of Kendall Mountain on the east side of the canyon, between the pre-Cambrian Irving group and die overlying volcanic tuffs and flow-rocks of the Silverton Caldera which form Kendall Mountain. There are numerous pits and quarries in the carbonate members of the section in this area.

Paleozoic formations in the lower section include the Leadville Limestone, Oury Limestone and Elbert Formation, and the Ignacio Quartzite. The Ignacio can be traced along a pre-Cambrian angular-unconformity in the cliffs above the canyon all the way to Elk Park.

From the east shoulder and upper slopes of Sultan Mountain southward, the upper Paleozoic section occupies the broad "Molas Pass Plateau", on the west side of the Animas Canyon to Elk Park. These sedimentary sandstone, shale, and limestone rocks include the lower Permian and Pennsylvanian Rico, Hermosa, and Molas formations. Molas Creek drains a watershed underlain by these carbonate and clastic sediments

Hie Animas River canyon is cut in pre-Cambrian rock units from just inside the mouth of the canyon at the Champion Mine, all the way to Rockwood, near Hermosa. From mile post 495,25 to Elk Park, the canyon is cut in pre-Cambrian meta-sedimentary and meta-volcanic gneiss, amphibolite, schist, slate, and quartzite. The section to Elk Park includes the Irving Formation, and the Uncompahgre Quartzite. Where the Animas River valley encounters the resistant pre-Cambrian rock section, the river is abruptly forced into an extremely steep-walled canyon.

An angular unconformable erosion surface forms the contact between the Precambrian section and the overlying upper-Cambrian Ignacio Quartzite. The erosion surface can be traced along the west 38 canyon walls downstream of the Champion Mine. It is characterized by a smooth, adulating surface carved in the meta-sedimentary Irving Formation, beneath a quartz-cobble and pebble conglomerate at the base of the Ignacio sediments. Locally, the contact has been structurally offset several feet across younger vein/ dike structures associated with the porphyry intrusive on the flanks of Sultan Mountain, indicating a dilative emplacement ofthe veins. In all areas examined, compositional layering ofthe underlying Irving metamoiphic complex is sharply discordant to the overlying Cambrian sediments.

Surficial Geology The flat, broad floor ofthe Animas River valley from Eureka to Howardsville is underlain by a thick deposit of glacial outwash and alluvium. Braided sections ofthe stream in this reach indicate the fluvial process is dominated by an abundance of sediment. Large debris and alluvial fans cover the valley floor at the mouths of all the steeper tributary gulches on both sides ofthe valley, including at Minnie and Maggie Gulches, and Porcupine, Brendel, Otto, Cataract, Hematite, Swansea, Idaho and Boulder Gulches.

Downstream from Howardsville to below the confluence of Arrastra Gulch, the river enters a narrow bedrock canyon section carved into the valley floor. On the lower valley slopes in this canyon reach are extensive deposits of glacial till and colluvium. The hummocky deposits form heavily forested, bench-like shoulders above the valley bottom along the footslopes of King Solomon, Hazelton, and Kendall Mountains. These deposits also mantle the lower slopes of Storm Peak and Anvil Mountain on the north side of the valley at Silverton, near the cemetary. Alluvium and outwash again underlie the wide valley floor at Silverton from the confluence of Cement Creek to the mouth ofthe Animas Canyon at the Champion Mine. MINERAL CREEK SITES TiONGFELLOW-KOEHLER

TCe Longfellow-Koehler (L-K), mine area lies immediately adjacent to the east side of US hwy. 550, 400 yards south ofthe summit of Red Mountain Pass, at an elevation of 11,160 feet. The site is situated on privately owned patented lode mining claims at LAT.N37°53 44 , LONG. W107 4240 .

Geologic Setting

Bedrock Geology The Longfellow-Koehler site is situated across the noith-westem margin ofthe Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Caldera rocks at the Longfellow-Koehler site consist dominantly of medium to dark brown and black, thick, massive ihyodacite and dacite flows and flow breccia of the Bums Formation. In the marginal ring-faulted zone, numerous dikes and plugs of much younger quartz-latite-porphyry (qlp), have been intruded into the flows and breccia. Although there are local variations in texture and mineralogy of the dark volcanic flows within the caldera, they are generally too localized and discontinuous to map, and are not important in an areal context. The L-K site lies at the contact of a topographically prominent intrusive quartz-latite-poiphyiy plug with ring-faulted caldera flows and flow breccia at the margin of the Silverton Caldera, The intrusive body forms a nearly vertical c liff on the east side o f the site, into the base o f which two adits have been driven south eastward. Within and along the margins o f the intrusive qlp plug are a system o f altered, highly mineralized volcanic breccia pipes. These pipes and associated veins were developed by mining operations at the L-K site.

Mineralization is typical of the Red Mountain Pass District quartz-alunite epithermal deposits. Sulphide minerals found on the mine dumps include pyrite, enargite, covellite, and chalcopyrite. The deposits were mined in veins, breccia pipes, and as disseminations in wall rock, intensely altered to silica, alunite, and clays. There are essentially no buffering carbonate minerals associated with these types of deposits.

Structural Geology Structurally, the site lies across a complex system o f ring-fracture faults related to subsidence o f the caldera. The feults trend north 22°east through the site, and are associated with a belt o f scattered, highly mineralized altered breccia pipes. These volcanic pipes are the hosts for rich silver sulphide ore deposits known in the Red Mountain Pass district. They probably occur here because the fractured, weakened zones at the margin o f the caldera allowed upward venting and movement of epithermal ore bearing fluids and gasses. The faults are generally vertical to steeply east-dipping, with the sense of movement being downward toward the center o f the caldera (east side o f each fault). Numerous mineralized fault and fissure veins trend parallel to sub-parallel with the ring- ftacture pattern through the L-K area, most showing similar sense o f displacement.

A second mineralized fault set in the L-K area trends almost perpendicularly across the dominant northeast-southwest ring-fracture pattern. One o f these fault veins stnkes south 76°west extending from the margin o f the intrusive porphyry across the southern part o f the site 200 feet south of the Koehler Tunnel portal. This fault can be traced west at the surface all the way across and beyond Mineral Creek. It appears to be acting as a preferential groundwater flow path; on the north side the water in ponds and seeps adjacent to it are visibly red, have acid pH, and high metals. Just south of the fault trace, another pond and seep appear to have normal, non-acidic waters. It is possible that contaminated water from the L-K site is intercepted and conveyed over to Mineral Creek along this particular fault, and possibly others.

Surficial Geology The ground surface along strike of the faults and mineralized veins forms a series o f narrow valleys separated by low bedrock ridges. The L-K site is located in one o f these fault-strike valleys adjacent to the intrusive plug in the ring-feult zone. Discontinuous pockets o f unconsolidated pebble and cobble gravels, colluvium, and glacial till are found scattered in the narrow valleys. A small pocket o f alluvial gravels lies adjacent to the Koehler Tunnel dump on the west side. Closed depressions within the valleys are occupied by ponds or wetland areas. The acid pond on the L-K site was a natural pond prior to mining activity as indicated by the thick black organic soils exposed below the mine waste on the northern shore.

Talus deposits have accumulated at the base o f steep cliffs around the intrusive porphyry at the L-K site. These rockfall derived deposits form extensive, thick aprons o f unsorted, angular angular cobbles, boulders, and huge slabs o f the resistant porphyry on the east side o f the site, partially burying the Koehler Tunnel portal, and extending down to blanket the east shore o f the pond.

BONNER M IN E

Location The Bonner Mine area lies adjacent to the Middle Fork, Mineral Creek on the steep southern valley wall at LAT. 1$37o50'39'', LONG. W107°44'12". Elevation across the site ranges from 10,040 ft. at the creek to 10,400 ft. at the upper mine level. The site is accessible via a jeep trail which leads south o ff Ophir pass road 0.72 miles above Burro Bridge.

Geologic Setting

Bedrock Geology The Bonner site lies just west o fthe Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Bedrock at the surface is the San Juan Formation, which here consists dominantly o f volcaniclastic, reworked, crudely bedded conglomerates, sandstones, and mudflow breccia o f dark andesite and rhyodacite clasts. Geologic mapping and examination o f the mine dumps indicates that the workings cut younger flows and breccia o f rhyodacite and dacite o f the Bums Formation in the subsurface. The Bums unit overlies the San Juan Formation, and consists o f flow massive aphanitic and porphyritic andesite and rhyodacite volcanic rock.

Mineralized veins worked at the Bonner appeared to be related to localized light colored rhyolitic and quartz latitic rocks. Sulphide minerals found on the dump include pyrite, sphalerite, chalcopyrite, and galena in seams in the light colored vein rock. The mine lies in the zone o f propylitically altered volcanic rock, (rock which has been hydrothermally altered to include one or more minerals o f the assemblage calcite, chlorite, epidote), and thus there is some buffering capacity from carbonate minerals. Gangue minerals consisted o f quartz, calcite, and rhodochrosite. Secondary alteration products included sodium sulfate salts, limonite, goethite, andpyrolusite coatings. Scree and talus are locally strongly cemented by iron oxides, forming ferricrete deposits on and at the base o f the valley slope.

Structural Geology Structurally, the Bonner site lies at the western edge o f the caldera. Prominent graben-like nng-faults at the caldera margin lie 1,500 feet west o f the site. The feults strike due north across the mouth of the Middle Fork valley, and are vertical to steeply east-dipping, with the sense o f movement being downward toward the center of the caldera (east). Numerous mineralized fault and fissure veins trend parallel to sub^arallel with the ring-fracture pattern through the Bonner area, most showing similar sense of displacement.

Surficial Geology Slopes at tli© Bonner site are steep. Talus, scree, and colluvium cover much o f the surface, becoming thicker at the foot of the valley wall. Much o f the colluvium and scree have been cemented by iron oxides, forming resistant ferricrete deposits. There are three springs just below the access road near the lowest adit level, and several more along the creek banks which appear to be draining metals laden water. The lower adit is portaled in an iron rich-conglomeratic ferricrete.

Alluvial gravels are present along the creek at the north end o f the site under and adjacent to the lower mine dump. There are also limited areas of dark black wetland soils along the creek.

The avalanche danger at this site is moderate; an active chute which has run in the recent past crosses the upper main mine dump, where it encroaches into the steep chute on the east side o f the site. At this time the chute does not extend above timberline, and does not have a large source area. Avalanches are thus confined, and consist of only the snow which falls in the chute itself. The volcanic conglomerates, breccia, and tu ff are cut by numerous mineralized feults and fissure veins. One o f these veins was prospected and mined for sulphide ores at the Bonner mine

R UBY TRUST

The Ruby Trust mine adit lies on the Middle Fork, Mineral Creek on the steep northern valley wall at LAT N37°50'xx" LONG, W107°44'xx", adjacent to the Ophir Pass road 1.7 miles above Burro Bridge. Elevation of the portal is 10,500 ft. The site is accessible via a short jeep trail which leads o ff Ophir pass road.

Geologic Setting

The Ruby Trust adit lies west ofthe Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Bedrock at the site is the San Juan Formation, which here consists dominantly of volcaniclastic, reworked, crudely bedded conglomerates, sandstones, and mudflow breccia o f dark andesite and rhyodacite clasts. The workings may intersect riiyodacite flows and breccia o f the Bums formation in the subsurface, but this could not be confirmed from examination ofthe dump materials.

Mineralized veins worked at the Ruby Trust appear to be related to mineralized fissures in the volcaniclastic rocks. Sulphide minerals found on the dump include pyrite and minor sphalerite, however, the dump is mainly waste country rock and does not contain a large proportion o f sulphide minerals. Mineralized veins appear related to localized light colored rhyolitic and quartz latitic rocks. The mine lies in the zone of propylitically altered volcanic rock, so there is some buffering capacity from carbonate minerals. Gangue minerals consisted o f quartz, calcite, and rhodochrosite.

Structural Geology «, 0 1 .. ^ u -ru Structurally, the Ruby Trust site lies 1.5 miles west o f foulted margin o f the Silverton Caldera. The marginal faults strike due north across the mouth o f the Middle Fork valley, and are vertical to steeply east-dipping, with the sense o f movement being downward toward the center o f the caldera (east) Numerous mineralized feult and fissure veins trend parallel to sub-parallel with the rrng- fracture pattern through the Ruby Trust area, most showing similar sense o f displacement.

The contact between the overlying Bums formation volcanic flows and the older San Juan volcaniclastics is close to the site ofthe adit, and may have been intersected by the workings, This unconformable contact could be a major groundwater conduit, which would explain the high flows o f near neutral pH water discharging from the workings. It is also possible that a major water­ bearing fault zone was intersected which resulted in flooding and abandonment ofthe operation.

Surficial Geology „ . . ... * Slopes at the Ruby Trust are steep. Scree, glacial drift, and colluvium cover much ofthe surface becoming thicker at the foot ofthe valley w all Large glacially deposited, rounded to sub-rounded boulders, as well as angular rock-fall-derived boulders from the peaks above are present on site. The adit is portaled in unconsolidated gravelly colluvium and glacial deposits, which have collapsed and sealed the workings. Springs issue from the collapsed material about 12 feet above the adit level, suggesting there is a large pool behind the blockage at the portal. Alluvial gravels are present along the creek at the south end o f the site downslope from the mine dump. There are also limited areas o f dark black wetland soils along the creek.

The avalanche danger at this site is high; two active chutes run on either side, and the open slope aspect is conducive to avalanches.

Mine Features The volcanic conglomerates, breccia, and flows are cut by numerous mineralized faults, fissure veins in this area. One of these veins was prospected and mined for sulphide ores at Ruby Trust site. There is one adit level driven northerly into the valley wall. Judging from the size o f the mine dump which is estimated to have been on the order o f 10,000 cu.yds., their are several thousand feet of workings in the valley wall. There do not appear to be any other openings to this mine, and the lack o f any strong sulphide ores or minerals on the dump seem to confirm old reports that it may have been a stock scam operation, Miners may have intersected a large water bearing zone which caused them to eventually abandon the work.

PARADISE MINK (cikaWhite Death)

Location An unnamed series o f portals informally nicknamed the "White Death" site is located on the Middle Fork, Mineral Creek, at its confluence with the Crystal Lake tributary, LAT. N37°50'34", LONG. W107o45'50". Elevation at site is 10,640 ft. The site is accessible only via a cross country hike down steep mountain slopes, south from the Ophir Pass road, or bushwhacking up the creek bed from the Ruby Trust site downstream. The site lies at creek level below uniform, very steep mountain slopes. The site lies in an active avalanche run out zone, with at least 4 individual chutes impinging on it.

Geologic Setting

Bedrock Geology The White Death site lies west o f the Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Bedrock at the surface is the San Juan Formation, which here consists dominantly o f volcaniclastic, reworked, cmdely bedded conglomerates, sandstones, and mudflow breccia o f dark aphanitic andesite and rhyodacite clasts. The Contact o f this unit with the overlying Bums formation runs through the site. The Bums Formation consists of massive flows o f aphanitic and porphyritic andesite and rhyodacite volcanic rock. An outcrop on site reveals a crude layering o f these flows, striking N50°W, dipping lO^orth.

Mineralized veins worked at the site appeared to be related to localized fissures. Sulphide minerals found on the dump include pyrite, sphalerite, and some minor galena in light colored vein rock. One o f these pyritic veins outcrops on the north side o f the creek, and was drifted on by a short prospect adit. This vein strikes N80°W, dipping 85°north. Gangue minerals consisted o f quartz, calcite, and minor rhodochrosite.

Structural Geology Structurally, the White Death site lies 2 miles west o f the margin o f the Silverton Caldera, on the contact o f the Bums and San Juan formations. Numerous,steeply dipping mineralized feult and fissure veins trend roughly noith-south through the area, parallel to sub-parallel with the dominant ring-fracture pattern on the margin o f the caldera. Cross-fissures at roughly right angles to the north- south are also common, though less persistent. The exposed vein prospected on the north side o f the creek belongs to this set of fractures . Surficial Geology . n • Slopes at the White Death site are extremely steep, at about 40 /o grade. Talus, scree, and colluvium cover much o f the surface, becoming thicker at the foot of the valley wall. Much o f the colluvium and scree have been cemented by iron oxides, forming resistant ferricrete deposits. A thick mantle of unconsolidated, bouldery glacial till and colluvium rests on bedrock west o f the creek confluence with the stream from Crystal Lake. Within the base o f this deposit is a natural femcrete cemented zone perhaps 2.5 to 3 feet thick, developed in the colluvium and glacial materials.

There are three springs upstream from P4 adit which appear to be draining metals laden water. Thin cobbly alluvial gravels lie along the stream bed, but bedrock outcrops are common. Four active avalanche chutes dump directly into the site, including the stream bed itself which leads avalanches down from Paradise Basin. There are piles o f rocky debris and tree trunks and limbs scattered over the site by avalanche activity.

BANDORA M IN E

The^'andora Mine lies on the South Fork, Mineral Creek 2.2 miles above the South Mineral Campground at LAT. N37°20'59", LONG. W108°34'28". Elevation ranges from 10,690 ft. to 11,000 ft. at the upper mine level.

Geologic Setting

Bedrock Geology , • c r __ The Bandora Mine lies west of the Silverton Caldera, near the western margin o f the San Juan Volcanic field. Hie mine workings are driven into the Cretaceous Dakota group sedimentary rocks, consisting o f sandstones and shales which have been exposed beneath the overlying Ternary volcanic sequences by down cutting o f the South Fork valley through the margin of the votcamcs. Cretaceous strata here strike S57°W, dip 1B°N, and have been intruded and contart-metamorphosed into homfelsic, slaty-shales and sandstones by the adjacent Rolling Mountain stock, a large intrusive porphyry body o f Oligocene age. Dump materials suggest this intrusive was cut by the Bandora mine workings in the subsurfece, though the surfece contact lies -500 ft. south west o f the mine portal. The basal Telluride Conglomerate unconformably overlies the Cretaceous section just above the upper most portal level, and is in turn overlain by the San Juan Formation Volcamclastic sequence. Numerous natural springs with relatively high flows were evident at the base of the Tellunde Conglomerate unit at its contact with the Cretaceous strata in the steep gully adjacent to the site on the north east. The Homfelsic strata at the mine site was apparently cut by mineralized fissure veins associated with intrusion of the poiphyry. These veins, as well as mineralized zones along the contact o f the intrusive and sedimentary strata were developed by the Bandora Mine. Sulphide minerals found on the dump include disseminated pyrite, minor sphalerite, and very minor galena. Gangue minerals consisted of quartz, calcite, and disseminated pyrite in blocky weathering homfelsic shale and sandstone.

Surficial Geology Slopes at the Bandora are steep. Talus, scree, and thin colluvium cover some o f the surface, but the site is dominated by rock outcrop.

A large debris-flow fan deposit lies just below and northeast o f the portal area. This thick, extensive sub-angular bouldery, cobble- gravel fan complex is derived from repeated flows and rockfall from the steep gulches draining o ff Fuller Peak and its east ridge. Large rockfall boulders rest within and on the surface ofthe fen, which extends down valley from the site for 0.5 miles. Debris flows occur frequently each spring along the gulch which bounds the mine site on the northeast, delivering ever more coarse sediment to the foot slopes o f the valley wall Alluvial gravels are present along the creek at the east side o f the site. There are also extensive wetlands along the creek below the mine site.

The avalanche danger at this site is minimal; an active chute runs in the steep ravine on the northeast edge ofthe site, but the mine itself is outside any avalanche zone.

NORTH STAR MINE

Location The North Star Mine is adjacent to Mineral Creek 3/4 mile above its confluence with the Animas River at Silverton. The site lies at the northern foot o f Sultan Mountain. Geologic Setting

Bedrock Geology The North Star site lies on the southern margin o f the Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Workings were driven southwesterly into a locally extensive porphyritic intrusive quartz monzonite o f Oligocene age. This intrusive body o f rock lies along the southern margin ofthe caldera, extending south to comprise Sultan Mountain. The intrusive body is separated from massive rhyodacite caldera flows and breccia on the north side o f Mineral Creek by a graben-like ring-feult system beneath the valley floor.

Numerous mineralized fault and fissure veins trend parallel to sub-parallel with the ring-fracture pattern through Sultan Mountain, most showing similar sense o f displacement. Sulphide minerals found on the dump include pyrite, sphalerite, chalcopyrite, and galena. There is little alteration o f the country rock here, and therefore limited buffering carbonate minerals are present in the gangue. Gangue minerals consisted of mostly quartz, with very minor calcite and rhodochrosite.

Structural Geology Structurally, the North Star site lies at the southern margin o f the Silverton Caldera. Prominent graben-like rmg-imilts at the caldera margin lie beneath the North Star site. The faults strike northwest-southeast along the base o f Sultan Mountain. Mineral Creek runs along the ring-feult structure, defining the southern boundary of the caldera. The faults are vertical to steeply north- dipping, with the sense of movement being downward toward the center o f the caldera (north). Numerous mineralized fault and fissure veins trend parallel to sub-parallel with the ring-fracture pattern through the North Star area, most showing similar sense o f displacement.

Surficial Geology The North Star site is mantled with thick glacial drift. The till is an unsorted, homogeneous deposit o f large boulders, cobbles, and gravel-sized clasts in a gray siJty-clay matrix. Hie deposits are quite extensive, extending upslope 1000 feet from the creek bed, and may be up to 50 feet thick along the lower foot slopes o f Sultan Mountain. Talus, scree, and colluvium cover much ofthe slopes above the glacial deposits. A large, active debris-fen bounds the mine site on the west at the mouth o f the steep ravine on the north side o f Sultan Mountain. The deposit consists o f large boulders, cobbles and gravels deposited by debris flow and avalanche activity. The ravine is also an active avalanche chute, but does not directly affect the mine site.

Alluvial gravels are present along the creek at the north end o f the site under and adjacent to the large mine dump, which partially blocks the present active stream channel o f Mineral Creek.

CARBON LAKE

Location The Carbon Lake mine area lies ‘/Smile east o f US hwy. 550 near the top o f Red Mountain Pass in San Juan County, at an elevation of 11,500 feet. The site is situated on privately owned patented lode mining claims at LAT. N37°53'45", LONG. W107°42'20".

Geologic Setting

Bedrock Geology The Carbon Lake site is situated just inside the northwestern margin o f the Silverton Caldera, a regionally prominent Tertiary-aged volcanic center. Caldera rocks at the Carbon Lake site consist dominantly o f medium to dark brown and black, thick, massive rhyodacite and dacite flows and flow breccia o f the Bums Formation. In this marginal ring-faulted zone, numerous dikes and plugs of much younger quartz-Iatite-porphyry (qlp), have been intruded into the flows and breccia. Although there are local variations in texture and mineralogy o f the dark volcanic flows within the caldera, they are generally too localized and discontinuous to map, and are not important in an areal context.

The Carbon Lake site lies at the contact of a topographically prominent intrusive quartz-Iatite- porphyry plug with ring-faulted caldera flows and flow breccia at the margin o f the Silverton Caldera. The intrusive body is elliptical in plan, 2,000 feet wide and 3,500 feet long, oriented parallel to the caldera margin. It forms a steep, prominent topographic high on the west side of the site. Within and along the margins o f the intrusive plug are a system of altered, highly mineralized volcanic breccia pipes and mineralized faults. These pipes and associated veins were developed by vertical shafts at the Carbon Lake site.

Mineralization is typical of the Red Mountain Pass District quartz-alunite epithermal deposits. Sulphide minerals found on the mine dumps include pyrite, enargite, covellite, and chalcopyrite. The deposits were mined in veins, breccia pipes, and as disseminations in wall rock, intensely altered to silica, alunite, and clays. There are essentially no buffering carbonate minerals associated with these types of deposits.

Structural Geology Structurally, the site lies just east o f a complex system o f ring-fracture faults related to subsidence or the caldera. The faults trend north 22°east, and are associated with a belt o f scattered, highly mineralized altered breccia pipes. These volcanic pipes are the hosts for rich silver sulphide ore deposits known in the Red Mountain Pass district. They probably occur here because the fractured, weakened zones at the margin of the caldera allowed upward venting and movement o f ore bearing fluids and gasses. The foults are generally vertical to steeply east-dipping, with the sense of movement being downward toward the center o fthe caldera (east side o f each fault). Numerous mineralized fault and fissure veins trend parallel to sub-parallel with the ring-fracture pattern through the Carbon Lake area, most showing similar sense o f displacement. Slickensides exposed in a silicified, brecciated fault zone strike N30°E, dipping 67°east.

A second mineralized fault set at Carbon Lake trends along the small stream draining the site, forming the creek bed and banks. These fault veins strike almost due east-west, but curve northwards at their ends, mirroring the contact o f the elliptical porphyry plug. It is likely that contaminated water from the Carbon Lake site is intercepted and conveyed to the groundwater system along these faults in the stream bed.

Surficial Geology

There are almost no surficial deposits at the Carbon Lake site. Nearly everywhere, volcanic bedrock is at or just beneath the surface. Thin, patchy colluvium lies on some o f the gentler slopes, and on the foot slopes around the porphyry plug. Natural wetlands existed along the small stream in the mine area, but vegetation was killed by runoff from waste piles, and the thin soils have subsequently been partially eroded. There is not enough suitable unconsolidated material on-site for revegetation or capping work. REFERENCES Bove, D.J., et al, 1999, Geochronology o f late Oligocene through Miocene volcanisim and mineralization in the western San Juan Mountains, Colorado: U.S.G.S. OFR-99-Q347

Burbank, W.S.,1933a Vein systems o f the Arrastra Basin and regional geologic structure in the Silverton and Telluride Quadrangles, Colorado: Colorado Sci. Soc. Proc., v.13, no. 5

Burbank, W.S.,1951, The Sunnyside, Ross Basin, and Bonita fault systems and their associated ore deposits, San Juan County Colorado: Colorado Sci. Soc. Proc., v. 15, no 7 U.S.

Burbank, W.S., and Luedke, R.G., 1964, Geology o f the Ironton Quadrangle, Colorado: U.S. Geol. Survey Map GQ-291,

Burbank, W.S., and Luedke, R.G., 1969, Geology and ore deposits o f the Eureka and adjoining districts, San Juan Mountains, Colorado: U.S. Geol. Survey Prof Paper 535

Fetchenhier, S., 1999, Ghosts and gold, the history o f the Old Hundred Mine: Lead Dog Communications, 143pgs

King, W.H., and Allsman, P.T., 1950. Reconnaissance o f metal mining in the San Juan region, Ouray, San Juan, and San Miguel Counties, Colorado: U.S. Bur. Mines Inf. Circ. IC 7554

Marshall, J., Zanoni, Z „ and Melcher, J., 1996, Mining the hard rock: Simpler Way Book Company, Silverton, CO, 216 pgs

Plumlee, G.S., Streufert, R.K., et al, 1995, Map showing potential metal-mine drainage hazards m Colorado, based on mineral-deposit geology: U.S. Geol. Survey Open File Report 95-26

Ransome, F.L., 1901, A report on the economic geology o f the Silverton quadrangle: U.S. Geol Survey Bull. 182

Steven, T.A., Lipman, P.W., Hail,W.J. Jr, et al, 1974, Geologic map o f the Durango quadrangle, southwestern Colorado, U.S.Geol. Survey Map 1-764.

Barker, Fred, 1969, Precambrian Geology ofthe Needle Mountains, southwestern Colorado: U.S. Geol. Survey Prof. Paper 644-A.

Luedke, R.G., and Burbank, W.S., 1975, Preliminary map ofthe Silverton Quadrangle, Colorado: U.S. Geol. Survey Open File Report 75-433, scalel:24,000

Osterwald, D.B., 1995, Cinders & smoke, a mile by mile guide forthe Silverton and Durango narrow gauge railroad: Western guideways, ltd.

Steven, TA ., Lipman, P.W., Hail,W.J. Jr, et al, 1974, Geologic map ofthe Durango quadrangle, southwestern Colorado, U.S.Geol. Survey Map 1-764. Stover, B.K., 1995, Geology o f the Animas River Canyon, Silverton to Rockwood Cut: Colo. Div. O f Minerals and Geol. Open File Report, prepared for Animas River Stakeholders Group; Map, scale 1:24,000

Stover, B.K., 1998, Structural geology of the Animas River Canyon, Silverton to Elk Park: Colo.Div. O f Minerals and Geol. Open File Report, prepared for Animas River Stakeholders Group, Map scale 1:12,000

Stover, B.K., 1999, Geologic transect o f Mineral Creek, Red Mountain Pass to South Fork: Colo. Div. Mins. & Geol, OFM-99-Ol, Open File Mapping, prepared for Animas River Stakeholders Group

Stover, B.K., 1999, Geologic transect of Ross Basin and upper Cement Creek: Colo. Div. Mins. & Geol OFM-99-02, Open File Mapping, prepared for Animas River Stakeholders Group

Varaes, D.J., 1963, Geology and ore deposits of the south Silverton area, San Juan County, Colorado: U.S.G.S. PP 378-A A PP E N D I X 7 B

H istorical Accounts o f W ater Q uality

i n t h e Anim as R iver Basin 1878 -1991

Prepared for the Animas River Stakeholders Group

Prepared by Michael Black June, 1994 H I S T ORICAL ACCOUNTS OF THE ANIM AS RIVER

The London Field. Oliver North. Mav 4 1878

The Animas rises in the heart o f the Rocky Mountains an, after a course o f a hundred and fifty miles through the most romantic scenery, empties itself into the San Juan River. There are no fish for the first half or so o f its course owing to the numerous canyons and falls; but the lower half affords very good sport - not so good as is made out to be. The fish rarely go over 1 LB although now and then a two pounder is basketed.

The Southwest (Animas City). Mav 1880

Advertisement: Rico House... at the junction o f Rico and Silverton roads - one half days travel from Rico or Silverton.

Tourists and others w ill find this the best point to explore the grandeurs o f the Grand Canyon o f the Animas, only one half mile distant, also near good fishing ground.

La Plata Miner. August 14 1880

A few trout at high prices have made their appearance in Silverton markets within a day or two, but we no sabe!

Several Deer and one large elk were seen recently on Anvil Mountain, but as a general thing wild animals or game o f any kind keep a good distance away from settlements and trails.

Fishing expeditions and berrying parties to the fish lakes and the Animas Valley are in order nowadays. Still the results o f these various trips have not so far panned out very extensively in either fish or berries.

Mr. Ross M iller who is rusticating in Silverton went on a fish excursion down valley this week.

La Plata Miner. Nov. 6 1880

(Silverton’s water supply. Article is complaining about lack o f water and suggests Boulder Creek as a water source.

La Plata Miner. Nov. 6 1880

Article describes Durango less than a month after being laid out. “ The (Animas) River is well filled w ith trout, much larger than are seen in our northern streams.” Dolores News. September 24 1880

(From the Durango Southwest) Mr. John A. Dramer o f Animas City was appointed U.S. Deputy Fish Commissioner and is authorized to prosecute all violations that come under his notice. The cooperation o f the public is all that is necessary to preserve the fish in our streams from extermination by vandals.

Durango Herald. June 1 1882

Fishing is clearly against the law but we saw 2 orderly looking men going towards the river with game baskets and fishing poles over their shoulders. What could they have been after.

La Plata Miner. A pril 26 1884

YE GODS and LITTLE FISH The Honorable F. Marion Snowden has been in receipt during the past week o f several telegrams from Col. J. Webb Collins, asking him to make preparations for stocking various streams in this vicinity, such as Boulder, Arastra, and Cunningham with mountain trout for which purpose 20,000 w ill be furnished by Col. Sesty o f the Fish Commission...

Mr. Snowden... appointed fish commissioner for San Juan County.

La Plata Miner. March 21 1885

STOCKING THE ANIMAS FORTY THOUSAND YOUNG BROOK TROUT PLACED IN THE ANIMAS On Wednesday last there arrived from Denver 40,000 young trout destined for the Upper Animas and the non mineral bearing streams emptying into it...

The first stop was made this side o f the slaughterhouse, where 6 or 7 thousand fish were placed in the stream... the last batch were placed in Boulder Gulch. The fish sent here are known as the red speckled eastern brook trout...

Quite a number o f people in speaking o f the matter on Wednesday expressed the belief that trout could not exist in the Animas, giving as reasons that the elevation was too great, that none had ever been seen and some that the water was too cold...

It has been impossible for fish to get into the upper Animas because o f the falls this side o f Rockwood, and even had they gotten past the falls, the strongly mineralized water from Cement and Mineral creeks would have driven them back... The fact is that the upper Animas River is regarded as one o f the best streams in southern Colorado fo r the propagation o f trout. The water is as cold and pure as can be found anywhere and there are no frogs, snakes or larger fish to feed upon the young trout. There is little fear o f the fish working below the confluence o f Cement Creek and the river, as the water at this point is so strongly impregnated with mineral that they w ill turn back and avoid it all together. La Plata Miner. March 21.1885

Some o f the young trout placed in the river on Wednesday were seen yesterday, they seem to be thriving and w ill no doubt get along well.

La Plata M iner. March 28. 1885

The young trout placed in the Animas River last week are gradually working up the river Parties have seen them a mile or so beyond the point where Boulder Creek empties into the river. They seem to be thriving remarkably well.

La Plata Miner. April 4 1885

One o f the fish planted in the Animas was caught. “ A speckled beauty.”

La Plata Miner. July 18 1885

R.H. Rohrig has purchased 35 acres o f bottom land adjoining Reese and Clemmons addition and proposes to dig four ponds upon the property and stock the same with fish. The ponds w ill be supplied by a large spring which is up on the property, and runs the entire length. Mr. Rohrig thinks that if the fish lakes are healthy for food surely the altitude o f Silverton ought not to be too cold this winter. The Same argument might be applied to the fish in the upper Animas, which were placed last winter, and are reported as thriving wonderfully,

La Plata Miner. Oct. 16 1886

R.A. Rohrig has associated himself with a partner in the cultivation of fish in his new fish ponds. There w ill cut 4 ponds of about an acre in extent each and improve the entire tract owned by Mr. Rohrig. Several varieties o f fish w ill be raised.

La Plata Miner. Nov. 13 1886

Rohrig’s fish pond is not such a success as that gentleman might wish. The ground at the bottom is porous and allows the water to seep away. Mr. Rohrig w ill line the bottom with cement if the soil does not get more solid.

San Juan (S ilverton! A p ril 28 1887

R.H. Rohrig petitioned the Fish Commissioner Whitehead for 20,000 trout and German carp. Mr. Rohrig has 2 fish ponds, one 500 yards long and the other 50 feet long by 20 wide and four feet deep. These ponds are kept pure and fresh from a flow ing spring that discharges a quantity o f water every day. San Juan. Mav 5 1887

Rohrig paid $100 for 20,000 fish.

San Juan. June 2 1887

R.H. Rohrig w ill arrive this week w ith 20,000 trout fo r his fish ponds.

San Juan. June 23 1887

R.H. Rohrig returned from Denver bringing with him 60,000 fish. The superintendent o f the state hatchery at Denver accompanied him to see that the fish were properly taken of.

Mr. Rohrig says that if the county w ill pay the expense o f getting the fish here he w ill let 40,000 go as 20,000 is all he needs fo r his ponds, otherwise he w ill take them all.

We believe it would be a good scheme to stock the Upper Animas with trout and the commissioners can do so at a very low cost to the county.

Silverton Democrat. June 25 1887

R.H. Rohrig returned from Denver and brought 60,000 fish for the purpose o f stocking the waters o f the Animas. State Fish Commissioner Whitehead accompanied him.

San Juan. July 14 1887

The ditch is running, much to the delight o f the small boy, whose tendencies induce him to practice piscatorial sports with bent pin hooks.

R.H. Rohrig has some very neat cards out announcing his readiness to undertake any business in the line o f ichthyology. We recommend him.

Louie Rohrig reports the fish which he lately put into his ponds in a flourishing condition and growing nicely, none o f them having died, since putting them into the water, and the prospects are that he w ill be able to furnish the market with fish shortly.

Silverton Democrat July 23 1887

The fish put in the creek that runs through Mr. Rohrig’s ranch are doing finely. Not a single fish out o f the 20,000 put in the lake and stream has died and they have been in four weeks. There is an iron spring just at the edge o f the creek in which the fish are located and a deep hole into which the water from the iron spring runs the fish w ill congregate in great numbers. So that Mr. Rohrig has come to the conclusion that fish are not averse to mineral water. M r. Rohrig says that he has plenty offish in his ponds from four to six inches long. He feeds them regular,

San Juan. September 1 1887

Louie Rohrig had better look out or some of our piscatorial experts w ill be up to his fishing ponds catching trout.

San Juan. September 8 1887

A trip to Mr, Rohrig’s fish ponds on the Animas River above town is a pleasure all our citizens should take advantage of, especially those interested in the success o f Mr. Rohrig’ s experiment.

Last spring, this gentleman sent to the State Fish Commissioner and procured 20,000 trout, among which were a few California Brook Trout.

The water of the ponds which Mr. Rohrig put the fish was heavily impregnated with iron and at the time caused considerable discussion, as it was generally supposed that the trout would not live in iron water.

San Juan. October 20 1887

Mr. R.H. Rohrig has a fish which he killed in his ponds up the Animas yesterday which weighs just 8 ounces.

Before Mr. Rohrig purchased his fish the ponds in which he placed them had direct communication w ith the river. When the ponds were screened off, several trout, which M r. Snowden had placed in the river 3 years ago and were left in the ponds, and it was one o f these M r. Rodrigo, killed. He says he saw one truth in his pond at least 4 inches longer than the one he killed. This one now measures 10 and V2 inches.

Report o f Explorations in Colorado and Utah During the. Summer, o f 1889, W ith an Account o f the Fishes Found in Each o f the River Basins Examined by David Starr Jordan_pg. 25 sec. 15

Rio de las Animas Perdidas. The Animas River is the largest tributary o f the San Juan. It rises in the mountains above Silverton. Above its canyon o f the “Lost Souls” it is clear, shallow, and swift, flowing through an open canyon with a bottom o f rocks. In its upper course it is said to be without fish, one o f its principal tributaries, Mineral Creek, rising in Red Mountain and Uncompahgre Pass, being highly charged with salts o f iron.

In the deep and narrow “ Canon de las Animas Perdidas” are many very deep pools, said to be fu ll o f trout. A t Animas City, above Durango, the stream enters a stony mesa, a glacial moraine, which, by its dam, has formerly made a lake of Hermosa Park. From this point, for miles below, the bottom is so covered by boulders that seining is impossible. At Durango the river is 2 to 3 rods wide and 2 to 4 feet deep; in the deeper holes, 6 to 8. The temperature is about 68 degrees. The stream was seined at various places from Animas City to a point about 5 miles above Durango.

At Durango, it is said that the large suckers (X. cypho [Razorback Sucker], C. latipinnis) and the “White Salmon” (Ptychocheilus [Colorado Squawfish]) ascent the river in the spring, going back to deep water after spawning in the summer.

Silverton Standard. June 21 1890

Louis Rohrig is busy making a new fish lake up the river near his present pond. It w ill cover two acres and Louis9 intention is to put boats on it a make a pleasure resort. The fish are looking well, but a number o f them made their escape this spring due to the pond overflowing.

Silverton Standard. June 28. 1890

Louis Rohrig wanted to let a contract this week for finishing his fish pond but the contractors wanted the meat market and sheep herd in part payment. Louis has concluded to wait a while as he is not ready to go out o f business yet.

Silverton Standard. July 26 1891

Louis Rogrig informs us that the fish in his pond have commenced to increase. For the first time this week he noticed some young trout. They are about h a lf an inch long.

Silverton Standard. May 30 1890

Louis Rohrig had the misfortune to lose all the fish out o f his pond this week. A ditch running from the upper slaughterhouse overflowed his pond and the water ran over the dam and the fish all escaped into the river. The loss is a heavy one on Louis, who spent several thousand dollars on the work of raising fish.

Four years ago he purchased the first fish and since then the business o f raising them has been a continual expense. This year the fish would have been large enough fo r market and from now on the pond would have been a source o f revenue.

Silverton Standard. July 30 1892

Capt. P. Stanley on his last visit to Denver arranged w ith the State Fish Commissioners to build a hatchery here. He was promised 25,000 trout and all the spawn he needed i f the county could find a location and donate the $100 towards the expense o f the necessary building.

Louis Rohrig very kindly donated the use o f his pond fo r three years and the Board o f Commissioners have consented to donate $100 whenever the money is needed. Capt. w ill go to Denver in a few days and complete the arrangement and we may expect to have the hatchery completed and the first fish inside the next 60 days.

Silverton Standard. August 13 1892

Fishing parties are now in order, some taking in the Rio Grande while others stay at home and try the Animas.

The Southwest (Durango). March 22 1893

M r. Herr has succeeded in getting the b ill passed establishing a fish hatchery in Durango.

Great Southwest. April 20 1893

State Fish Commissioner W.R. Collicote o f Denver is here to locate and establish a fish hatchery. The gentlemen in company with the Honorable Sam Herr are about today with a view o f deciding on a suitable location.

Daily Southwest (Durango). June 28 1893

The meeting o f all those interested in forming association to aid in the enforcement o f the state fish and game laws occurs this evening in the Durango Club rooms. Honorable Sam Herr and others w ill be present and state the purposes and plans o f the organization.

Daily Southwest. June 29 1893

AN ORGANIZATION EFFECTED TO PROTECT FISH AND GAME Those who wish to have one o f the most attractive features to the tourists o f this section protected by local organization. Mayor Kephart, President W.T. Kirpatrick, Vice President J.L Parsons, Secretary Geo. Raymond, Treasurer F. Boyle, T.C. Graden, C.F. Wynn, Howard Charton, B.R. Coulson, George Weaver... Strong local adjunct to the assistance o f state game laws to be formed.

Daily Southwest. July 1 1893

W.C, Metcalf returns from a days fishing trip near Pinkerton Springs with a record o f fifty-eight trout landed in six hours o f sport.

Daily Southwest. July 27 1893

M r. and Mrs. Hall, E.C. Fearing, and M r. Joseph H all started this morning fo r the vicin ity o f Hermosa to camp out and fish. Boating is becoming quite popular and canvas canoes on the Animas are plying the river almost incessantly. Perhaps as another means o f diversion they have come to stay, or it may only be a passing fad end when the novelty has worn away.

Daily Southwest. August 24 1893

Mr. John Meuser of Durango appointed Deputy Fish Commissioner...

Daily Southwest. August 25 1893

Charles Starr and I. Harry Oarker were arraigned... arrest made... at the insistence o f J.L. Parsons representing the game and fish protection association.

Daily Southwest. August 27 1893

Charles Starr and Harry Parker... were convicted... having in their possession mountain trout killed in State o f Colorado and offering to sell... his testimony was that the defendants brought seven trout to his saloon on August 24 and represented that they caught them in the Florida... the defendants swore the fish were caught in a slough ofthe Animas River above town... 90 days in ja il... they wanted 50 cents.

D aily Southwest. September 26. 1893

The fish hatchery matter should be attended to promptly. La Plata County cannot afford to lose the plant.

Several citizens have already expressed their willingness to contribute liberally to the fish hatchery fund. It would be worth thousands o f dollars to this section o fth e state i f the streams were stocked with fish as fully as in the early days. The fish hatchery w ill do it... The securing ofthe fish hatchery in this county was a matter o f considerable difficulty.

San.Juan. County in the 1890’s Published Silverton Standard 1899

Our county has a population o f 4,500. In production o f gold it stands fifth in the state, in silver seventh, lead third, copper second.

The mineral resources o f San Juan County, however, are merely in the preliminary stage o f ascendancy, deep m ining... w ith three exceptions, namely those o f Silver Lake, the Iowa and Empire Consolidated.

Sunnyside M ill #1 capacity 30 tons/day; Sunnyside M ill #2 150 tons/day; Gold King M ill at Gladstone 125 tons/day with 10 new stamp mills in place by spring; Silver Lake 200 tons/day; North Starl25 tons/day, (All these mills dumped tailings and slimes directly into the Animas.) Durango City Council Minutes. April 17 1900

Prof. Larch addressed the council upon the question o f making mineral and sanitary tests o f the water.

Durango Citv Council Minutes. August 12 1900

(Discussion o f survey o f further water supply - pipeline 10 miles long and reservoirs.)

Silverton Standard. August 17 1901

We understand that 40,000 trout w ill be placed in South Mineral Creek waters by Fish Commissioner Day next week. South Mineral Creek is a fine stream and does not contain m ill tailings, although by the time the minnows have grown to fish hood estate there w ill be m ills in that section also.

Silverton Standard. August 24 1901

The chemical tests o f Boulder Creek show it to be nearer absolutely pure than any other known stream in Colorado.

Durango Citv Council Minutes. Mav 9 1901

Pay all expenses o f the Water Committee and Citizens Committee investigating the means o f stopping pollution o f the Animas River.

Durango City Council Minutes. July 2 1901

Discussion o f water problems, proposal to buy reservoirs on the Florida.

Silverton Standard. July 12 1902

Protests in Durango newspaper about drinking water,

Durango Evening Herald. July 18 1902

Nor is there any way to prevent the mischief (pollution) unless the mills were shut down permanently and all industry in that area stopped...

If, as is claimed, the mineral solution in the water hurts the crops, then the real question to be discussed and settled is, which is o f more importance to this western section o f the state, the mills which form the industry of the little northern towns or the acres o f land under cultivation for miles down the Animas Valley.

Remark to a Silverton citizen... the answer was given “ why it is only the natural ore from the earth that goes down; the river is constantly in its native element flow ing through those substances.” That was a rather lame excuse for the mineral in its native bed o f rock which takes centuries for the rushing torrents to wear away is quite different from a powdered gold, iron, lead, copper, silver, coke, cinders, quartz, lime, Soil, and what not that trickles down in a grand mass.

Durango Democrat. August 1 1902

The Animas River is maintaining a larger flow than even the San Juan, and Durango’s future for water depends upon enforcing the law as to polluting streams, adding the required pumping capacity, and an additional or settling reservoir. There is non impurity in the water other than such as the slimes and mineral that go w ith the m illing process.

The citizens o f Durango demand an injunction restraining the mills o f San Juan County Colorado from polluting the waters ofthe Animas with m ill tailings. A permanent restraining order and we are paying our good money monthly to City Attorney M iller and District Attorney for just such protection.

It may be w ell for or district attorney who does not want the office, and our city attorney who w ill hook into anything in the shape o f our office, to hook into the fact that the mills guilty o f polluting the waters ofthe Lake Fork ofthe San Miguel have been promptly closed down until settling reservoirs can be built.

Durango City Council Minutes. August 5 1902

A communication from J.H. Lynch representing Turtle Filtering Co.... asking that this council send a sample o f Animas river water for analysis.

Durango Democrat. August 6 1902

CITY COUNCIL PROCEEDINGS VISITING COMMITTEE OF ALDERMEN FIND DEPLORABLE CONDITIONS IN SILVERTON AND SURROUNDINGS. ... Mr. Darlington was asked for the report o f the committee who went to San Juan County to investigate the pollution ofthe Animas River and the adjacent streams. He said in part: “ We went to the Silverton mills and were permitted to go up Cement Creek to the Gold King. We found that the tailings were run into the creek which empties into the Animas. A ll the water closets stand over the stream and the cook house refuse is dumped into the stream. I talked w ith M r. Kinney and he said the tailings did not injure the water and gave me to understand that if it wasn’t for the San Juan M ills there would be no Durango, which at the present time owes its existence to the mills. I f they were made to impound the tailings there would be no ore from that section shipped to Durango as it would be cheaper to build a road to Lake city than to impound the tailings and that’s what they would do. Despite this talk, we were treated nicely at this plant. Next we went to the Silver Lake Mine and investigated thoroughly as Supt. Pickrell showed us the way. The tailings are dumped directly into the Animas as w ell as all refuse from cook house and closets. A t Eureka we found two m ills, one on the Animas and one on a small stream nearby. A ll tailings go directly into the Animas and the closets are situated on the river bank. At the Iowa mine the tailings are impounded on a lake, but the water from the mills empties into the river. At another m ill known as the North Star, the tailings are dumped into the Animas. At this m ill they are situated so they can hardly do otherwise. At eureka Judge Terry could easily utilize a flat that is below his mills for the tailings. At the Little Dora the tailings go direct into the Animas. The Silverton sewerage runs into a little stream that flows into the Animas but the worst sight that met our gaze was the Silverton Dump. There we found a dead horse, a dead cow and manure galore, some o f the refuse lies in the water at its present low stage. I f the whole river was to raise two feet, the whole dumping ground refuse would come our way. The two little streams that some time ago were allowed to run through the street have been shut o ff as the tailings stopped the flow so much that it caused too much trouble.

The district attorney came in fo r a share o f sarcasm from Darlington and the others and the city attorney did not escape in the long run.

Darlington made a motion that when City Attorney M iller returns that he start injunction suits against all the m ills in San Juan County that pollute the waters o f the Animas River and adjacent streams and including the city o f Silverton.

The resolution to go after Silverton mills and their reckless system o f dumping garbage so as to poison and pollute the streams was the unanimous act o f the council... now get a lawyer who is not running his office fo r vote and go after them.

Durango Democrat. August 7 1901

We are unprepared to believe that any fair minded citizen o f Silverton w ill approve dumping stable refuse, dead animals, garbage etc. into the river or on the banks o f any stream.

In reading over Mr. Johnson’s card you w ill notice that he made no allusion to the sub treasury scheme, Philippine “water cure” or the propriety o f soliciting Silverton’s permit to remain on the earth, at least until B ill Z. Kinney gets his aerial route ballasted with hot air.

Silverton’ s method o f dumping is purely criminal and absolutely without excuse, a wanton assault on human health. There is no m ill in San Juan that can not flume the tailings to some point instead o f directly into the river, and as a flume w ill last fo r fifteen years the expense w ill be light, the benefits great.

Mr. Johnson is fearful o f incubating ill w ill in Silverton. Well when we have to accept m ill tailings, broncho juice and stable refuel and other refuse as the price o f peace there is going to be a scrap. Silverton m ill men and garbage dumpers should be called down and at once. We are weary o f any and all in the way o f additional procrastination.

Silverton mines should be allowed a reasonable time in which to divert the m ill tailings; they should be allowed no time as to altering their method o f disposing o f garbage and dead animals and after a reasonable and fair period as to the mills the injunction should become permanent and effective. We are against any and all pollution o f streams and dead against a reckless and premeditated practice that is ruining human health and damaging the property o f hundreds o f residents who reside along the Animas River. It is clearly criminal and under the law cannot be tolerated by the people. B ill Kinney was down from Silverton yesterday to see about ties for his Lake City road but he couldn’t exactly figure out what he wanted with the ties and finally decided to price a pile driver and get estimates on the logs for the aerial route. B ill has all the requirements essential to the success in the newspaper business - and then some.

RANCHERS ON POLLUTION Animas Valley farmers are very naturally worked up over the pollution o f the Animas River, both as to domestic and irrigation use. They say the law should be enforced and are in the city daily to ascertain why not. They were in the valley farming long years before Silverton had a m ill and naturally object to being ruined in health and purse in order that Silverton’s heavy mine owners may profit by their destruction... Place the residents and mine owners o f San Juan County in our condition and observe the howl that would go up. Every hour that injunction proceedings are delayed is an hour devoted to a compromise with crime.

Durango Democrat. August 10 1902

I f our friend B ill Kinney is chasing after an injunction precedent we cite him to the one he ran on the Sampson mine fo r dumping tailings into the stream above his property.., The Gold King folks are the authors o f the first injunction against tailings and the first to flume them from their mill.

Durango Democrat August 13 1902

There w ill be no change o f water system unless by and w ith the consent o f the taxpayers and there can be no charge as satisfactory as one that gets us on a water power basis. The Animas is a ll right and always w ill be if the work of polluting the streams with tailings and in various other ways be enjoined.

Durango Evening Herald. August 14 1902

SILVERTON MILLS AND DURANGO

The former (tailings) are coarse and heavy and soon sink to the bottom o f the river, the slimes are very much diluted and are light, rising to the top o f the water and are carried to greater distances...

The city attorney (Dgo) says that he has always insisted that accurate data were needed.

JUNCTION CREEK UNDER FLOW

Several years ago an analysis o f this sort was made (a complete mineral) and resulted in favor o f the river water, but at that date the Animas was an altogether different stream from what it is today.

Then it came down from the mountains in all its pristine clearness, there being very few m ills or causes o f contamination o f any sort above Durango. I f the courts grant the injunction the waters o f the Animas say whether or not it is being obeyed. The m ill owner is the precise individual who allows the tailings to enter the river; there is no wrangle over the sewage that flows in through the pipes. The court w ill make an injunction effective by making it permanent.

The Florida water supply is not arranged, just the Cascade and the Animas and the under flow (Junction Creek) is suggested. There is nothing more certain than that the taxpayers w ill ra tify or reject any or all bonded indebtedness. But how about the injunction the “ windy ignoramuses” want?

Silverton Standard. August 16 1902

Thursdays Durango Herald brings the information that the city council o f that town has ordered its attorney to commence suit against the miners and the city o f Silverton for the pollution o f the streams that drain the river and the river itself. But in striking contrast to the agitation o f the Democrat, the Herald shows the futility o f attempting to purify the water o f the Animas without shutting down the m ills.

The alleged wanton pollution o f the waters o f the Animas by the m ill owners o f San Juan County and the people o f Silverton is only in the jaundiced vision o f the editor o f the Durango Democrat. So seriously is the Democrat taken in Durango that District Attorney Charles A. Johnson, who by the way is a stockholder in that paper, in an able article shows how absurd are Colonel Day’ s howlings. Mr. Johnson resents the idea that it is his duty as District Attorney to commence criminal proceedings against certain people in San Juan County and tells the Democrat in effect that i f it is bound to stir up strife between two communities, the proper way is to ask for an injunction. Mr. Johnson intimates that even the stopping of the mills w ill not remedy the evil and free the Animas River water from the impurities created by the large populations and live stock. Local physicians who have given some thought to sanitary engineering inform us that even were the m ill tailings impounded, the waters with which they were handled(?) would still carry the objectionable impurities to the main stream and pollute it practically as much as the tailings do.

It is up to Durango people to compel the mills o f the San Juan County, those that could do it, to impound their tailings and still have an impure water supply, or go to the several available sources near Durango, and secure a supply o f good water.

Durango City Council Minutes. August 23 1902

The special committee reported that two gallons o f the Animas water had been forwarded to the Turrdale Filtering Company and a like amount to the State Dairy Commission and letters written to said parties asking fo r an analysis.

The clerk was instructed to write Von Schultz and Low, chemists, o f Denver and ascertain their charges o f making an analysis o f the waters o f the Animas.

The city attorney recommended filin g fo r water and reservoir sites on Cascade Creek The Durango Republican “Parson Lou” Smith’s paper is the latest Durango concern to go on record in the opposition to the Democrats’ fight against the m ill owners of San Juan County. Colonel Day’s issue is as dead as Tracy, and Tracy is mighty dead.

Silverton Standard. August 30 1902

A t an adjourned session o f the Durango C ity Council, a committee was appointed to obtain samples o f the Animas River water which w ill be sent to an expert chemist fo r analysis.

Durango City Council Minutes. September 2 1902

Von Schultz and Low, 1746 Chauipa St., Denver, Colorado

$50 to detect sewage contamination by study o f organic matter present. To ascertain various constituents o f the mineral a mineral analysis is necessary - $50/sample. Analysis made at the intake. I f contamination found it w ill be necessary to make tests up the river above all reasonable sources o f impurity in order to ascertain if the Silverton sewage and slimes from the mills affect the water.

Durango City Council Minutes. September 16 1902

Communication from J.H. Lynch o f Turrdale Filtering Company in which he stated an analysis had been made o f the water o f the Animas R iver... and that a considerable quantity o f lead and arsenic had been found.

Silverton Standard. September 27 1902

Tim Malone's fishpond is the pride o f the old man’s heart. It is not much o f a pond to be sure but the little creek that comes into the Animas between the old Reid M ill and the lime kiln furnishes the home for several families o f mountain trout.

Durango City Council Minutes. October 7 1902

Cost o f pumping water 7 & K cents/1000 gallons

Durango City Council Minutes. October 211902

Proposal to sell reservoirs and water rights from the Florida River to the city.

Durango Democrat September 30 1902

Alderman Naeglin... stated he had not drank any Animas City water since visiting Silverton. Durango City Council Minutes. October 28 1902

#1 and #3 priorities on the Florida River, reservoir on reservoir h ill to store 183,565,910 gallons,

Ordinance 390 Question o f whether a gravity system o f water works should be provided. (Florida River)

Durango Democrat November 2 1902

THE WATER QUESTION

Fifth. Is the bonded proposition to mean that the Animas River is to remain a sewer for m ill tailings, to the detriment o f the valley farmers upon whom we depend fo r produce and trade?

We are violently opposed to allowing the Animas River to be destroyed by m ill tailings and polluting agencies... And if there is a law to prevent pollution o f the Animas, in God’s name let it be enforced.

Durango Citv Council Minutes. November 4 1902

Council responds to article in the Durango Democrat on Florida water rights. Print and distribute “ dodger” to answer questions.

M otion to purchase Boyle Morgan water rights on Florida and submit to voters.

Durango Democrat. November 12 1902

There is no citizen o f Durango who ever heard a bitter or even passing protest against Animas River water until the mills in Silverton began to pollute the river with m ill tailings.

The Almighty never intended that mankind should destroy so beautiful a stream, w illfu lly and recklessly destroy it. It is an outrage upon the residents o f Durango o f the valley to permit it.

Durango Democrat November 15 1902

Silverton should be forever restrained from dumping any m ill tailings into the Animas River or its tributaries. This much should be accomplished at once and without any ceremony or apology.

Durango Democrat November 18 1902

Silverton m ill owners w ill no doubt swell over the loss visited by the impoundment o f tailings, but it w ill just have to be that way. The San Bernadino mine folks put up just such a w all, but we notice they got the tailings under control w ithin tw o days after Judge Stevens got after them. A glimpse o f the Animas River w ill convince even the policy Aleck that we are a patient people to submit to such a w illfu l and unlawful pollution o f that beautiful river. We owe it to ourselves and to the valley farmers to protect them.

Durango City Council Minutes. November 18 1902

(Form Dodger on Florida River Water Supply) To citizens and taxpayers o f Durango. With reference to the proposition submitted by the City Council to the voters as to whether a gravity system o f water works should be constructed...

The water shed from which these reservoirs are supplied re composed entirely o f granite and the water is at all times, even at high stages clear and pure.

(They used Cascade Creek as the only alternative.)

The cost o f maintaining the present pumping system... the annual cost steadily increased with the increase in consumption while (up to the capacity o f the proposed conduit which is sufficient for a supply six times as great as present demands) the cost o f maintaining a gravity system would not be increased by the increase in consumption.

The condition o f the Animas River fo r domestic supply has been steadily going from bad to worse and is such to apparently demand that a different supply be secured.

(The plan included 4 reservoirs and necessitated buying up a ranch on the Florida.)

Durango Citv Council Minutes. May 19 1903

$300 appropriated for the purchase o f the fish hatchery

Silverton Standard. August 26 1933

LOOKING BACKWARDS TEN YEARS AGO (Aug. 192)

40,000 native and rainbow trout fry were received yesterday from the Durango hatchery. They were placed in Molas Lakes, Little and Big, and the South Mineral Creek.

Silverton Standard. June 2 1934

LOOKING BACKWARDS TEN YEARS AGO (1924)

Commissioner Edward Meyer, Sheriff Kearney and L.W. Parcell distributed 60,000 trout fry last week. 36000 went to Molas Lake and the remainder were placed in South Mineral Creek. LOOKING BACKWARDS TEN YEARS AGO (1924)

Robert Burnell Jr., W illiam Stanger and Frank Salfsberg spent Friday fishing in the Needleton country.

Silverton Standard. September 22 1934

LOOKING BACKWARDS THIRTY SIX YEARS AGO (1898)

George Jew and Sam Dresback are taking a few days outing in the Animas River Canyon. They are armed with fish hooks and Winchesters.

Fort Lewis College Oral History Lester Short. December 9 1991

Linda: So you could drink this water? (Florida)

Lester: Yeah. The Florida River, you see, was always a clean river. It was never polluted. The Animas River at that time, you didn’t do anything with the Animas River. The m ill tailings were running into it. I ’ve seen it run plum green, and o f course Durango was dumping its raw sewage into the river, so down here (Sunnyside on Florida Mesa south o f Durango) why you didn’t even swim in the Animas. There wasn’t any fish in it, there wasn’t anything, it was really a dead river.

Linda: This was when you were a child, a young man would you say?

Lester: Yeah.

Linda: The when were changes made to clean up the Animas?

Lester: Well later on the m ill tailings were, of course the mines sort of slowed down, and they weren’t doing much. Then we began to have laws saying they couldn’t put their m ill tailings in the rivers any more. Couldn’t just dump it in the riv e r... A ll in all it just began to happen. The river got cleaned up and it’s a beautiful river now. It’s wonderful, but that wasn’t true at all when I say I was a kid. A PP E N D I X 7 C

H istory of M ining and M illing Practices and Production

I n t h e U noer Anim as R iver Drainage 1871-1991

Prepared for the Animas River Stakeholders Group Use Attainability Analysis

Prepared by William R. Jones, R. A. H IS T ORY of M INING & M ILLIN G PRACTICES & PRODUCTION I n T h e UPPER ANIM AS RIVER DRAINAGE 1871 -1991

Prepared for the Animas River Stakeholders Group - Decem ber 8, 2000

By William R. Jones, R. A.

PURPOSE

The purpose of this report is to identify the major historical mining and milling practices, technology, economics, and events that influenced mining production in the Upper Animas River Drainage, San Juan County, Colorado and their relationship and significance to water quality issues.

HISTORIC OVERVIEW

Silverton and San Juan County have a history o f m ining production that spans over 120 years, from initial discoveries in 1871 to the end of major production in 1991. During this time the industry evolved and grew due to a complex mix o f technology and economics influenced in the broadest sense by society’ s need for metals as America grew into an industrial and world power. The mining industry has always been a leader in technological innovation and the industry around Silverton was no exception. Four distinct historic periods of mining and milling practices can be identified. These four periods are sharply defined by the ore processing or m illing in use during the period. Mining techniques changed somewhat more gradually, but with a clear connection to the demands placed on the mines by the periodic rapid innovations o f processing technology.

Mining in Silverton followed the “boom and bust” pattern repeated throughout the West. Outside events such as war, depression, and government policies often triggered these cycles, which were quickly reflected in the price of metals. Mining in the district evolved from small “high grade” mines w ith lim ited processing, to larger mines producing lower grade ores, but at lower cost. This increasing output was processed in mills, which grew in size and efficiency. But unlike other mining areas, which continued this progressive increase in size, large San Juan mines reached an upper lim it o f 700 to 1,000 tons o f ore produced per day around 1920. Annual production in the district was remarkably steady at 200,000 to 250,000 tons per year when economic conditions were favorable. See chart o f Estimated Mine Production 1871-1991 below. Basis for calculating this data are discussed in the Endnote.

The sources o f mine production were varied, but soon a pattern developed that remained typical to the end o f major mining in 1991. One or two “large” mines would account for the majority of any single year’s production. After 1930 only two mines account for around 90% of all mined production, the Shenandoah-Dives (1930-1953) and the Sunnyside (1962-1991). Other earlier “large” mines include the Silver Lake, Iowa, Old Hundred, Gold King, and Gold Prince. Numerous small mines added to production during periods o f high metal prices or wars, only to close when prices dropped. The term “large mine” is relative to the historic period. In 1890, 100 to 200 tons per day was “ large” , by 1940, 500 to 700 tons per day was a “large” mine.

Note that the boundaries of the following four periods are not precise, and the technology and practices described tended to overlap somewhat into both prior and later periods.

Estimated Mine Production 1871-1991

PERIOD I - THE SMELTING ERA 1871-1890

A. MINING DEVELOPMENT & PRACTICES

The first mining was performed by hand methods in small operations producing only a few tons o f ore per day. Shafts or adits (tunnels) were excavated directly into exposed or near surface outcrops. Tunnels and shafts were short, typically not over a few hundred feet at most. Only the more valuable “high grade” ore was mined. Less valuable “low grade” ores and waste were typically left unmined in the vein when possible. No mechanical processing or milling was done at the mine. The best ores were sacked and shipped as “ crude ore” to smelters as far away as Wales.

Ores were typically hand sorted, meaning the best ore chunks were hand separated and shipped as “first class ore” . The sorting was done both underground in the mined out rooms called “ slopes” and at the surface. Often a slightly lower grade was sorted and shipped as “ second class ore” . Hand “ cobbing” upgraded lower grade ores by hammering o ff chunks o f good ore from the lower grade or waste rock. After the cobbed o ff chunks were sacked, the waste was left on the dumps. To provide a space to work o ff of, the stopes were fille d w ith waste and low-grade ores in a mining method called “cut and fill sloping” . Thus, the waste on the dump still contained a significant but uneconomic amount of mineral. Due to the difficulty in mining, little non- mineralized “country” rock was excavated.

As the period progressed, mines became larger as outside capital financed expansion o f existing and new mines. The Greene Smelter to process ores into metal opened in Silverton in 1875, which stimulated production. This smelter was moved to Durango in 1880 where coal was more plentiful. When the railroad arrived in 1882, mining increased dramatically as reduced transportation costs stimulated production. Ores were shipped by rail to the smelter in Durango for processing (Ransom 1901).

As the mines expanded production, milling and ore sorting practices continued as described above but on a larger scale. More men were employed in additional working areas to achieve this increase. Larger ore sorting houses were bu ilt at the mines. Mines typically produced tens o f tons of ore per day and by the end o f the period the larger mines were producing over 100 tons per day. By the close of the period, tunnels were often hundreds of feet long with multiple levels interconnected by internal shafts.

The federal government supported mining in several ways during this period. The General M ining Law o f 1872 had codified the ability to claim and later purchase government land for mining purposes. Purchase o f government land by individuals and companies was a primary tenet o f government policy throughout the late nineteenth and early twentieth century. It was one of the primary ways the government raised revenues prior to income tax. In 1877 the Bland- Allison Act directly helped silver mining by requiring the federal treasury to purchase a fixed amount o f silver for monetary purposes (Brown 1984).

B. MILLING DEVELOPMENT & PRACTICES

Most of the ores mined in the district were lead/silver ores with minor gold content. For this reason, direct smelting o f crude ores was the normal method o f processing. Only a few small gold mills were constructed in the later 1880's. The county produced little “free milling” gold ores which were common in other areas. Thus the “ stamp m ill” used throughout Colorado was less common in the area. A t least two small gold stamp m ills were bu ilt up Arrastra Gulch during this period.

C. ENVIRONMENTAL ASPECTS

Smelters in this and later periods could not treat ores containing over 10% zinc (Henderson 1926). The smelters levied stiff charges against zinc in the shipped ore. Therefore miners worked hard to leave the zinc in place in the mine or sorted and cobbed the zinc o ff by hand. The zinc mineral was disposed in the waste dumps at the mine and as part o f the waste ore used to fill the stopes. This “waste” still contained a relatively large amount of metal laden mineral. Thus significant mineralized material was left where surface and underground waters could potentially dissolve metals, particularly the discarded zinc.

The Greene Smelter and other pioneer smelters in the Silverton area emitted acidic and metallic containing flue dusts and gasses, which were probably distributed in the area soils. The Greene Smelter worked only intermittently over four years. The two gold mills built in Arrastra Gulch used the mercury amalgamation process. Tailings were discharged directly into the creek. Some mercury was probably introduced into the environment by these mills.

Total mined tonnage for the period 1874-1889 is estimated at 171,727 tons with most of this having been shipped to the smelters and only a small amount discharged as m ill tailings into the watershed,

PERIOD II - The GRAVITY MILLING ERA 1890-1915

A. MINING DEVELOPMENT & PRACTICES

During this period, mining development greatly expanded due to improved technology and government supports. In 1890 the Sherman Silver Purchase A ct was passed by Congress, as part o f a compromise to gain western mining states senators support o f tariffs desired by eastern manufacturing states senators (Brown 1984). This act guaranteed all silver mined would be purchased by the government. Colorado silver mining boomed. New technologies were also developed in this period. First, the wire-rope aerial tramway revolutionized transportation of ore, machinery, and supplies to remote mine sites above Silverton. Then compressed air powered machine drills increased tonnage produced underground. Narrow gauge railroads were extended into the valleys around Silverton directly to the mill sites and tramline terminals, further improving transportation. Finally, was the application of electricity to many mine and mill tasks. For example, the railroad brought coal to the tramline that was critical for the steam boilers at the mine site to power the air compressors for the machine drills, and generate the electricity to crush ore.

In the large mines, tonnages o f over 200 tons per day became practical and upward o f 400 men would work year around at a remote high altitude site such as Silver Lake or Sunnyside. Ore sorting in surface houses continued to intensify as increased mine tonnage yielded lower grade ores. Most mines s till used cut and f ill stoping. M illin g became more common as the tonnage increased and ore values dropped. Several classes o f ore were mined and sorted for both direct smelting and milling, depending on the grade o f the ore. Larger mines now had a few thousand feet o f workings on multiple levels.

Economic and political policies impacted mining during this period. In 1890 the government basically subsidized unlimited silver mining. This subsidy ended with the financial panic and ensuing depression of 1893-1896 and the price of silver fell sharply. Marginal mines were closed. Gold prices were still supported at $20 per ounce as part o f the monetary Gold Standard. Mining shifted focus to gold, lead and copper, rather than silver, The plentiful amounts o f base metal ore in Silverton kept the local industry stable, if not booming. After 1896, mining increased again when the U.S. economy expanded, only to be set back by the Financial Panic of 1907. The beginning o f World War One in 1914 led to a substantial increase in base metal prices resulting in the expansion o f many mines, notably the Sunnyside (Henderson 1926). In 1897 over B. MILLING DEVELOPMENT & PRACTICES

As mining technology advanced, milling technology also improved to cope with larger amounts o f low grade, metallurgically complex ores. Stamps were used to pulverize the ore but instead o f mercury to extract the gold, concentrating machines called “bumping tables” were used to separate the various minerals into "concentrates” containing mostly lead or lead/copper which the smelters could process. Any gold or silver would be recovered as part o f the concentrates. Various concentrating machines were developed and used differences in the ore’s specific gravity to separate the mineral particles hence the term “ gravity m illing” . By 1898 the “ W ilfle y Table” was established as the leader in the field. (Niebur 1986).

Mills, which had been a rarity in Silverton, were now built at every major producing mine. In 1890 the Silver Lake mine was the first to build a large 200-ton per day concentrating m ill on the shore of Silver Lake (Ransome 1901). The economic advantages of milling were significant. Low grade ores would be concentrated into high grade concentrates that could be sold to the smelter at a profit instead of discarded. Since smaller tonnages o f material went to the smelter, smelting and transportation costs were markedly reduced and net revenue increased. However, zinc ores were still unmarketable during most o f this period. In 1897 twelve mills and two crude ore purchasing stations called “ samplers” were reported in operation. The largest mills were 200 tons per day capacity, while most were around 50 tons. Combined total capacity o f the crude ore samplers was 200 tons per day and the mills 850 tons per day. Production was not continuous all year at all mills however. By 1901 additional mills increased combined active production to 1,470 tons per day with annual production exceeding 200,000 tons. In 1897 five o f the twelve mills included some mercury amalgamation as part o f the process. Two used sodium thiosulfate leaching to recover silver (CBM 1898 and Henderson 1926).

C. ENVIRONMENTAL ASPECTS

Environmental impacts during this period were primarily due to a greatly expanded scope. Techniques were similar to prior periods but on a larger scale through increased mechanization. Waste dumps from the sorting houses became large, some exceeding 50,000 tons. Water drainage became more o f a problem as longer tunnels impacted groundwater levels. When shaft mining was used, water infiltrating into the mines had to be pumped out. In the nearby Red Mountain Mining District, acidic water was a major problem and was commented upon in early literature. In Silverton, grossly acidic water appears not to have been a major problem. However, water infiltrating the “filled” type stopes could potentially pick up metal contamination. By the end of the period many mines were operated through long tunnels built at lower elevations, which tended to drain the ground water down to that level leaving upper mine workings relatively dry. Some o f these tunnels reached several thousand feet in length.

Increased milling during this period had a major impact on surface water quality. M ills produced a muddy slurry waste product called "tailings” . Tailings were usually discharged directly into a nearby stream or river. Sometimes they were discharged haphazardly on the ground or riverbanks. Stamp m ill tailings were like coarse sand. The ore particles were soft and tended to slime making recovery difficult for the W ilfley Tables. There was a tendency for the coarse sands to settle out more quickly in the river gravels, while finer material would stay suspended in the river for long distances, affecting water quality as far south as New Mexico, Gravity mills recovered only 60% to 80% o f the metals in the ore such as gold, silver, and lead. Zinc, iron pyrite, and a portion of the copper were not recoverable by gravity mills (Niebur 1986). Thus, significant amounts of metals were left in the tailings, and particularly the very fine “slime” particles that could be widely distributed into the aquatic environment. The water quality was degraded sufficiently in Durango to required ail entirely new reservoir and delivery system to be constructed on the Florida River to avoid the tailing laden Animas River.

At Silver Lake, the first m ill was located beside Silver Lake itself, and deposited tailings directly into the lake. About 500,000 tons were reported to be in the lake by 1903 (Neibur 1986). No mercury or other chemicals were used at this m ill (Ransome 1901). Improvements in milling technology resulted in about 400,000 tons o f these tailings being pumped out o f the lake between 1914 and 1919 for reprocessing in a new m ill along the Animas River. Although more metals were removed from the tailings, 500 tons per day o f these reprocessed tailing residues were then discharged directly into the Animas River near the mouth o f Arrastra Gulch (Neibur 1986).

Chemical reagents were not used in the typical gravity concentration mill, although mercury coated amalgamation plates were common. Mercury could be lost by physical attrition o ff the plates. Due to its high value, mercury traps and other recovery devices were incorporated into the m ill to keep mercury losses low. Particles o f mercury amalgam were also recoverable by the concentrating tables (Taggart 1927). This may help explain why mercury contamination has not been generally detected in the watershed. Sodium thiosulfate was used in tw o short-lived “ lixivation” mills but this is not an acutely toxic reagent.

Total tonnage for the period 1890-1915 is estimated at 3,898,971 tons with a large majority discharged as tailing. By comparison Henderson reported only 78,000 tons crude ore shipped during the 1909-1923 period.

PERIOD III - THE EARLY FLOTATION MILL ERA 1915-1935

A. MINING DEVELOPMENT & PRACTICES

In Europe, the First W orld War consumed huge quantities o f metals. The United States entered the war in 1917 and an already brisk wartime economy boomed. Base metal prices soared as the war continued to increase demand (Henderson 1926). Gold and silver were o f lesser importance at this time. Improvements in both smelting and milling, coupled with wartime demand made zinc ores a marketable commodity for the first time (Bird 1986). Mines with zinc, such as the Sunnyside expanded, w hile those without closed, such as the pioneering Silver Lake mine.

Because the new flotation m ill could do much o f the separation formerly done by hand sorting, mining practices began a major shift to larger scale “bulk” mining methods and away from more selective lower tonnage methods. The new mining method was called “ shrinkage sloping” . Here the entire vein was mined, instead o f only the best part. When the stope was completed, all the broken ore was removed from the mine leaving a large void. In the "cut and fill" stope, the void was left full o f low grade or waste material. No ore sorting was done and everything was milled. Average ore grade decreased, but so did the cost o f mining and m illing as tonnages increased and unit costs decreased. This was to become the dominant trend o f mining throughout the twentieth century both in Silverton and worldwide.

Other technological changes contributed to this increase in tonnage. Larger, more efficient compressed air drills replaced the early types. “Wet” drills increased productivity by reducing dust and improving working conditions for the miners. Mines continued to increase in length, depth, and vertical extent. The Sunnyside became the largest producer in 1916. B y 1917 its daily production increased to 500 tons. In 1918, 600 tons per day was reached and by 1927 over 1,000 tons per day was achieved (Bird 1986). Wartime prices also saw many small mines open and a new smelter even operated during the war years to treat pyritic copper ores from Red Mountain.

High metal prices caused by the war were unsustainable, and in 1921-1922 a sharp recession hit the country. Mining in Silverton collapsed. In 1921 the total year’s production was a mere 1,100 tons versus over 200,000 tons mined in 1920 (Henderson 1926). Mining recovered in 1923 with the re-opening of the Sunnyside but the character o f the industry changed permanently. Many small and medium sized mines closed for good, along with some older large mines such as Gold King in 1925. By 1930, only two mines dominated production for the next 61 years, while small mines played a decidedly secondary role. By the late 1920’s some new mines were begun as the national economy grew, notably the Shenandoah-Dives, Buffalo Boy, and Little Nation. But metals prices again collapsed with the onset o f the Great Depression in 1930. The Sunnyside closed in September 1930 leaving the one-year old Shenandoah-Dives mine as the only major producer for the next 23 years (Chase 1952).

B. MILLING DEVELOPMENT & PRACTICES

Ball m ill grinding and froth flotation for concentrating ores revolutionized milling after 1914. The sudden and widespread impact of this technology cannot be over emphasized (Rickard 1932). instead o f coarsely pulverizing ores with crude stamps, high capacity wet grinding with steel balls in a rotating drum created a uniform and finer product. Early flotation used bubbles in an acidified pine-oil/water mixture to float o ff and separate the valuable mineral particles from the worthless quartz. More importantly for Silverton, the process could separate zinc from the lead and copper, and worked well on troublesome “ slimes“ that gravity mills could not recover well. In addition new electrolytic smelting processes made the zinc concentrates produced by flotation marketable at last.

The first large scale mills for lead-zinc ores were built in Butte, Montana in 1914 using the patented Minerals Separation Syndicate process (Rickard 1932). Stamp m ills and W ilfle y tables quickly became obsolete for primary m illing o f base metal ores. The Silver Lake and Gold King mines in Silverton added experimental flotation sections in 1914 with Sunnyside following.in 1915 (Henderson 1926). It worked so well at Sunnyside the individual owners sold controlling interest in the mine to the U.S. Smelting and Refining Company. This large corporation had the financial resources to build a huge “ state o f the art” 750 ton-per-day flotation m ill at Eureka in 1917. The new m ill recovered up to 90% o f the minerals including zinc as a separate concentrate. Tailings now had less metal in them, but were finer in size, and the tonnage produced expanded to 1,100 tons-per-day in the 1920’s. W ilfley tables used in the new Sunnyside m ill were of secondary importance (Taggart 1927). The new m ill was the first large tead/zinc flotation m ill in the state and one of the first in the nation (Bird 1986). Most of the now obsolete gravity/stamp mills remaining in the district were closed by the 1921 recession, or soon thereafter and never reopened.

C. ENVIRONMENTAL ASPECTS

Mining continued the trend toward larger and more extensive workings, with more potential impact on groundwater hydrology. Very long tunnels such as the Gold King and Frisco were nearly a mile in length. Significant localized drainage of groundwater was now occurring with resultant potential for acidic or metal laden discharge into the creeks. Improved m illing had some indirect benefits during the period. Low-grade and zinc bearing ore was less commonly left in stopes or on dumps where it could come in contact with the environment instead it was being milled.

Flotation milling on the other hand had an increasing impact on the Animas River. Ball mill tailings were much finer than the old stamp m ill tailings. While the tailing contained less metal per ton, milled tonnage increased, yielding a net increase in tailing being deposited. The now finer tailings traveled farther and began to elicit serious, legal complaints from downstream water users in Durango and New Mexico. Sometime in the late 1920’s, downstream water users sued the Sunnyside mine’s owner, U.S. Smelting over the Eureka M ill tailing pollution (USS&R 1930). The main issue was sedimentation o f irrigation ditches, not chemical contamination. It is unclear if the case was actually tried, but the company prepared a vigorous defense. It hired Durango assayer A.P. Root to take weekly samples o f the river in Durango from March through September 1930, when the mine and m illed closed. These samples were stored under seal for the next two years as legal wrangling continued. Root’s field notes survive, and the river was typically described as “gray and turbid” during normal and low water flows. During high flow, the tailing’s gray color was obscured by natural sedimentation (Root 1930). Mining companies at the time typically argued these sediments were not harmful to fish or agriculture but the attitudes o f the courts and the public were changing (Smith 1987). The mining companies had successfully ignored similar complaints 25 years earlier.

The oil flotation process used various chemical compounds to make the process work, but their direct environmental impact is difficult to assess at this time. In the early Minerals Separation process, the m ill water was acidified w ith dilute sulfuric acid and pine-oil was added as the frothing reagent. Shenandoah-Dives used this pine-oil process for the first few years of their operation. Precisely what Sunnyside used in the 1918-1925 period is unknown, but lead/zinc m ill practice at the time used alkaline solutions rather than acidic. The 1926 m ill circuit and reagents are described in detail in Taggart’s 1927 Handbook of Ore Dressing. Reagents included small amounts o f coal tar, creosote, naphthalene, pine oil, and the new potassium xanthate as the main frothing reagents. Large amounts o f sodium carbonate (soda ash) were used to raise the pH. The xanthate chemicals, an alcohol-like liquid, were patented in 1925 and are the basis o f modem flotation, completely supplanting oil-flotation within a few years (Rickard 1932). It is worth noting today that in contrast to districts such as Telluride and Cripple Creek, there is no record o f direct cyanide milling for gold in San Juan County, probably due to its chemical incom patibility w ith zinc and copper in the ores. Total tonnage mined in the period 1915-1935 is estimated at 3,715,737 tons with nearly all o f that being milled and entering the river as tailings.

PERIOD IV. TIIE MODERN FLOTATION MILL ERA 1935-1991

A. MINING DEVELOPMENT & PRACTICES

The Great Depression was a very difficult time for base metal mines. Declining industrial production saw the lowest prices o f the century fo r silver, lead, copper, and zinc. Gold was an exception when the government devalued the dollar in 1934 by raising the price o f gold 75% from its long time $20 per ounce level to $35 per ounce. A ll gold was required to be sold to the U.S. Government or its authorized dealers, a regulation that lasted until 1971 (Smith 1987). This sparked a renewed interest in gold mine exploration but had no major impact on new San Juan County production due to the scarcity o f gold ore in the district. It did help keep Shenandoah- Dives, a low-grade gold mine, solvent and stimulated re-openings at the nearby Camp Bird mine in Ouray and several Telluride mines, which were later consolidated as the Idarado Mining Company.

Shenandoah-Dives survived by reducing per ton unit costs, chiefly by increasing tonnage mined and by improving the m ill. Starting at 300 tons per day, the mine soon changed to shrinkage stoping and increased production to 600-700 tons per day. Virtually every ton of rock broken underground was milled. As base metal prices slowly recovered in the late 1930’s, a few small high grade lead-zinc mines were developed such as the Pride o f the West, which built its own 50 (later 90) ton per day mill at Howardsville. The size and extent of the mines continued to increase. Shenandoah-Dives reached a vertical extent o f over 2,500 feet by 1941 and horizontal extent o f over 7,000 feet by 1948 (S-DM Co Reports).

The Sunnyside re-opened for about 18 months in 1937-38, but it closed due to sagging prices, high operating costs, and “excessive water which forced the.,.owners to abandon the work” (Standard Metals 1960). Soon the impact o f the Second World War began to affect the industry. When America entered the war after Pearl Harbor, the country was desperately short o f zinc and other base metals. In 1942 the government closed all gold mines so that scarce mining labor and resources could be shifted to base metal production. Shenandoah-Dives, a nominal gold mine, was ordered closed by the War Production Board (WPB). Shenandoah-Dives manager Charles A, Chase and Silverton leaders put political pressure on the WPB through Colorado’s governor and congressional delegation. The WPB actually re-wrote its national regulations in such a way as to permit Shenandoah-Dives to avoid the closure order {Mining World 1942). Silverton and the mine were saved, along with the narrow-gauge train, which later became the backbone o f the tourism economy in the region.

As milling technology improved and wartime demand increased, Shenandoah-Dives and other mines began to re-mine old underground stope “ fills” and surface dumps left by the old timers. In Dives Basin, Shenandoah-Dives recovered over 100,000 tons o f dumps left by turn o f the century ore sorting operations (S-DM Co Reports), This “dump recovery” was widespread in the county during World War II and the Korean War when surplus four-wheel drive trucks became available. Government policy further stimulated mining and dump recovery when it began to pay bonus price subsidies called “premiums” for every pound of metal mined. Road building and exploration were also subsidized by the U.S. Bureau of Mines through the Defense Minerals Exploration Act (DMEA). The Reconstruction Finance Corporation (RFC) actively loaned money for mining projects and the Metals Reserve Corporation bought metals and ores directly for strategic government stockpiles. Some o f these programs survived into the early 1960’s.

W ith such favorable economic and government policies dozens o f long dormant mines were re­ opened. Ore was shipped to the Shenandoah-Dives m ill for processing and when its capacity was reached, by rail to the Golden Cycle m ill in Colorado Springs. These mines were small, often mining only a few tons per day. Shenandoah-Dives remained the main producer at 600 tons per day with about 100 tons per day o f “custom ore” being milled in summer months for the small mines. The Pride of the West, Highland Mary, and Lead Carbonate built or expanded their own small mills and increased production during the war. Production would have increased more during the war, except for the shortage o f labor. Anecdotal evidence suggests the labor shortage was the main reason the Sunnyside never reopened during the war, despite large zinc reserves.

Shenandoah-Dives continued steady development o f its property and the adjacent Silver Lake mine into the early 1950’s. Metals prices again declined after the 1952 election due to a perception that President Eisenhower would soon end the Korean War. In 1953 the new Congress withdrew Korean War price supports for lead-zinc, Production at Shenandoah-Dives ceased in March o f 1953, which had the effect o f closing most o f the remaining small mines who were dependent on the Shenandoah-Dives m ill for processing. A government DMEA exploration grant kept the mine alive for a few more years though without production (USBM-DMEA 1955).

In 1959 a new company, Standard Metals Corporation, lessee o f the Sunnyside Mine, bought the Shenandoah-Dives mine and m ill and began w ork to extend the old Gold King Tunnel at Gladstone another mile under the long dormant Sunnyside. Improved mining technology now made such very long tunnels feasible. The work is described in the 1960 Standard Metals Corporation Annual Report

“The [American] Tunnel was driven in order to provide an economical means for removal o f ore as well as drainage. The original schedule for reaching the Washington vein was January 1961. This has been accomplished in spite of a water flow of 3,000 gallons per minute encountered from the 9,000 foot mark...... Prior to driving the American Tunnel, the drainage of eight million gallons of water in the Sunnyside mine workings was ... a potential major problem. Fortunately the tunnel intersected a fault zone with fissures resulting in a gradual drainage o f the old workings. The water level has been dropping an average o f more than three feet per day in the old Washington Incline [shaft]. At this rate, when the raise is ready for the breakthrough [into the old mine workings] the volume o f water remaining in the upper level w ill be negligible,” The tunnel’s ability to drain the workings proved successful, but would cause problems for later owners. Production from the Sunnyside through the 11,000 foot long tunnel began in August 1962 and continued at 700 tons per day, increasing to 1,000 tons per day for a few years in the late I970’s. Unexpected gold discoveries kept the mine going long after other similar base metal mines in the state closed.

Other than the Sunnyside, relatively little new mining was done in San Juan County after 1953 other than a few small mines that operated intermittently and some large exploration projects, In 1967 a Texas oil company called D ixilyn began a large exploration and development project at the Old Hundred mine. It found little ore but constructed over 15,000 feet of new tunnels. Significant drainage was also encountered as at Sunnyside, but water quality was better, About 20,000 tons o f dumps and ore were milled at the expanded Pride o f the West m ill. High gold and silver prices in the late 1970’s and early 1980’s caused another increase in exploration activity around Silverton. A few new access tunnels were built but again, little or no ore was developed or produced. Several old mines were explored but prices did not maintain a high level long enough to sustain major new mining development. Major mining was confined to the Sunnyside, which benefited from the high gold prices. Higher prices did mean mine dumps at Lake Emma and other locations were shipped and m illed at the old Shenandoah-Dives and Pride o f the West m ills.

In the late 1970’s new surface reclamation laws in Colorado began to affect ongoing mining operations. In 1983, aggressive legal action under the federal Superfund law against Newmont Mining’s nearby Idarado Mine in Telluride caused all major U.S. and Canadian mining companies then exploring in San Juan County to quickly terminate leases and activities. After 1984 no major U.S. mining company initiated any new activity in San Juan County due in large part to the underlying uncertainty of similar legal action. The continued exception was the Sunnyside, which was purchased by Canadian based Echo Bay Mines in late 1985 after the bankruptcy o f Standard Metals Corporation. B y 1991 its reserves were exhausted and the property went into reclamation. Low metal prices coupled with increasingly complex environmental regulations resulted in a cessation o f mining and exploration activity after 1991, following a pattern similar to other mining districts in Colorado.

B. MILLING DEVELOPMENT & PRACTICE

In 1935 the Shenandoah-Dives M ill was the only m illing operation in the watershed. As a result o f both downstream complaints and management’s personal philosophy, the first successful steps were taken to prevent major water pollution caused by m ill tailings. When the m ill was built in 1929, manager Charles A. Chase with the support o f concerned stockholders intended not to discharge tailings into the river at all, Instead special tanks and machinery were installed to settle the tailing and haul the sand back up the tramline, where it would be dumped as a surface pile thereby keeping it out o f the river. M ill water would be filtered and recycled. Unfortunately the equipment did not work, and being in financial difficulty, the company reluctantly discharged tailings into the Animas River as mills had before (Smith 1987). In 1935 Chase learned of a novel method o f tailing impoundment being used at Butte, Montana. The technique was adopted and after some experimenting was found both economic and effective. By 1936 nearly all their tailing was being retained in ponds, keeping them out o f the river (Chase 1938), In a tailing pond the tailing sand is used to build up a retaining dam while the slimes and water settle in a pond behind the dam. As it settles, the water clears, and can be decanted out into the river through pipes, devoid o f most mineral laden sediment. This basic method was used until the end o f m illing in 1991. W hile effective, the system was not perfect and the hillside where Shenandoah-Dives built its first pond was not conductive to structural stability. The sand wall on Pond #1 collapsed in 1947 and again in 1975 the latter collapse causing abandonment o f the pond. These accidents resulted in thousands o f tons o f tailing to enter Boulder Creek and then the Animas River. In 1947, the accident resulted in no legal or other complaints against the company, The pond wall was promptly repaired and the company even received a commendation for its pollution control efforts from the Colorado Fish and Game Department, By 1975 the story was different. Standard Metals was fined $25,000 for contaminating the river. This was the largest fine levied against a polluter in Colorado at that time. Active water quality monitoring of the tailing decant water became standard practice about 1977, w ith the advent o f the National Pollution Discharge Elim ination System (NPDES) permitting system.

From 1935-1991 milling technology was one of gradual improvement in efficiencies and equipment. Metal recovery was over 95% efficient by the 1940’s and only incremental changes were made into the 1970’s. The only major change was the abandonment in the mid-1930’s, of the old oil-flotation chemistry at Shenandoah-Dives, for the more efficient xanthate flotation reagents which allowed separation of a zinc concentrate. In 1965 Standard Metals noted in its annual report: “Tailing disposal systems were improved in line with current stream and river pollution regulations and practices.” Illustrating Colorado’s continuing efforts at water quality regulation prior to nationally mandated legislation.

During the period 1935-1991 an estimated 9,610,232 tons were mined and milled with all but about 200,000 tons o f tailing being impounded in tailing ponds.

Total production for the entire one hundred twenty-one year period (1871-1991) is estimated at 17,400,000 tons with an estimated 7,500,000 tons discharged directly into the watershed as m ill tailings.

B. ENVIRONMENTAL ASPECTS

In many ways mining’s impact on the environment lessened compared to earlier periods as attitudes and regulations changed, and practices improved. Also the number o f operating mines and prospects markedly decreased after 1953 as mining economics became less favorable. Underground practices continued much as in the past but longer, lower tunnels increased mine drainage discharges. Annual production remained about the same, averaging around 250,000 tons. Unlike other mining areas where mines continued to grow in size, even Silverton’s largest mines could not sustain production much above 700 tons per day for any long period o f time. Smaller mines dwindled in number except during the war years and no single small mine exceeded 100 tons per day o f new production.

The war years (1942-1945 and 1950-1953) resulted in significant road building, re-mining of dumps, and re-opening o f old mines. Little regard was made to the condition of the surface after such war inspired activities and most old stamp m ills were burned for their scrap metal. Some o f these sites resembled a war zone themselves after wartime scavenging o f ore and metal, Underground workings of the larger mines expanded to tens of thousands o f linear feet with many multiple levels continuing impacts on groundwater hydrology. Potential for metal laden drainage into the streams increased. Few new surface dumps were created during the 1935-1991 period since most mineralized material was milled. The several new access tunnels built did generate large dumps, but contained mostly un-mineralized “country” rock with only limited potential for environmental impact. Reclamation laws since 1976 have tended to minimized surface impacts.

Key legal actions in the 1930’s finally pushed the industry to find solutions to the tailings discharge problem. In March 1935, the Colorado Supreme Court upheld a lower court ruling against the Chain-O-Mines Company in Central City and ordered it to cease tailings discharges into Clear Creek (Smith 1987). Legal action was never taken against Shenandoah-Dives, who instead cooperated with downstream farmers and ditch companies to find a solution it could afford. Tailings ponds were begun in July 1935 and by June 1936 the m ajority o f tailings were retained. By August 1937, the system achieved “ complete retention” . As Manager Chase wrote in a 1938 article about the work; “Decanted water is, for the most part above reproach as to clarity. The Animas is reported a first-class fishing stream.” Still, noting new grass growing on the sand wall he wrote, “we may yet demonstrate to the farmers that they are deprived o f good soil building material” (Chase 1938). Charles Chase was ahead o f his time but still believed the tailings themselves benign or even beneficial. It would take future scientific research to dispel this opinion held so long by mine operators (Smith 1987).

When the Sunnyside reopened in 1937 tailing pond dams built with mechanical excavators were used to withhold the tailing in the flat gravels south o f Eureka. After the mine was abandoned and the Eureka m ill scrapped in 1949, these dams partly washed out and some o f the 1937-38 tailing re-entered the river. *

Other than the occasional accident or error, decant water quality varied due to a number of factors. Wind and thunderstorms would sometimes stir up the shallow water in the pond, allowing slimes into the discharge. Close attention by operators was needed to keep the decanted water clean. Occasional complaints were registered with the state and against Shenandoah-Dives and other 1940’s operators when conditions downstream deteriorated.

Chemical or metallic constituents of decant water were not regulated until the late 1970’s. Beginning in 1937, small amounts of cyanide (under 10 ppm) were used in the m ill water to depress iron in the flotation process (S-DM Co. Reports). Existing 1940’s correspondence from the state Fish and Game department to Shenandoah-Dives never mentions any concern over chemical contents. Presumably levels used did not cause any obvious problems to fish. Small amounts o f cyanide were used until the end o f m illing in 1991, though in reduced amounts as discharge regulations became more stringent. Even at the time o f the Shenandoah-Dives m ill’s final 1991 closure, the bio-toxicity of various mill reagents was not well understood. For example xanthate concentrations in m ill discharges were never regulated by state or federal agencies during the m ill’s operating life. Potential groundwater contamination by tailing pond deposits was not addressed by regulators or industry until the late 1970’s. Ponds built in prior years were not sealed and contact with groundwater or near surface waters under the pond was common. This contact can cause contamination through acid formation and leaching o f metals from the tailing. Though none of the older ponds were sealed to prevent contact with groundwater, not all old ponds resulted in any surface or groundwater contamination. Some tailing material contains sufficient alkaline minerals to neutralize acid formation.

One dramatic event did adversely affect the Animas River fo r a short time in 1978. Standard Metals was mining a gold vein under Lake Emma, located at 12,000-foot elevation in Sunnyside Basin. Unknown to the miners and geologists, thousands o f years before, glaciers had gouged a crack along the weak vein rock and it was filled with permafrost. Heat from the mine melted the frozen mud and the lake crashed through the mine on Sunday, June 4 , 1978 the only day o f the week no miners worked underground. An estimated 6,000,000 gallons o f water gushed out the American Tunnel into Cement Creek, and Terry Tunnel into Eureka Creek. The river turned black from the glacial mud and sediments well past Farmington, New Mexico. The towns of Durango and Aztec had to shut off water pumping plants to prevent the black water from entering municipal water systems.

A t the time o f the disaster, most downstream users and the press thought Lake Emma was fu ll o f mercury and metal laden tailings from an early Sunnyside mill. This was incorrect because the first mills were built down stream of the lake. In fact water from the lake was piped to a water wheel to power the stamps of the mill downstream (Bird 1986). The river was fouled with natural glacial sediments, diesel fuel oil from mine equipment, and a small amount o f fine sulfide ore particles from the mine and natural erosion in the basin. Large ore chunks from the collapsed stope never made it past the portal. No adverse environmental affects were noted and the company was not fined by any state or federal agency. The accident was determined to be an “Act of God” in a federal court action brought on by the mine’s insurance company against Standard Metals. The mining company demanded $9,000,000 in claims against their insurer for “business interruption” . Standard Metals won the suit. Water drainage was significantly altered in Sunnyside Basin but was largely mitigated through major reclamation efforts by later mine owner Echo Bay who ironically was not originally responsible for the problem.

Water drainage from long tunnels such as the American Tunnel became targets o f regulatory and environmental scrutiny when water discharges from mine tunnels became closely regulated in the 1970’s. Echo Bay is now working to eliminate this drainage by installing hydraulic seals in the tunnels. It is hoped this w ill prove a permanent solution to mining’s one hundred year battle with water and drainage problems, both operational and regulatory.

CONCLUSIONS

The history of mining and ¡milling practices in the Animas River watershed lead to a number of conclusions which may be o f value in examining water quality issues in the river basin today. Clearly mining and milling practices prior to 1935 were performed without regard to their environmental impact. Technological advances resulted in large-scale production after 1890, which tended to magnify this impact. The period 1890 through 1935 shows an estimated 7,500,000 million tons of tailing being directly deposited into the Animas River and its tributaries. This represents 43% o f the estimated 17,400,000 tons o f ore produced during the 121-year period studied. This tailing as well as surface mine dumps, often contained large amounts o f zinc and other metals un-recoverable at the time. Both coarse stamp m ill tailings and finer ball m ill tailings entering the river resulted in widespread distribution of mineral laden sediments that affected downstream water users as w ell as the area immediately downstream from a mill. This historic tailing disposal practice is probably one of the most significant factors affecting present day watershed ecology. Mine workings expanded in length, depth, and vertical extent over time, locally impacting groundwater hydrology and increasing direct mine drainage into the watershed. Not all o f these drainages were acidic or contained significant metals. Mine drainage may be the second most important aspect o f historic mining practices that affect water quality,

After tailing retention in ponds became standard practice in 1935, direct contamination o f surface waters by tailings was nearly eliminated. Accidents and operator error did cause occasional problems. Potential adverse effects caused by dissolved metals in the decanted tailing water and m ill reagents are unknown. M onitoring o f these discharges did not became mandatory until the late 1970’s. Likewise contact between tailing stored in the ponds, and underlying groundwater probably causes groundwater degradation in some but not all tailing ponds built prior to the late 1970’ s. By the 1930’ s less waste ore was being deposited on surface and in underground stopes, because most mineralized material was being milled. In fact, improvements in milling and periods o f metal price increases due to war or other factors resulted in several hundred thousand tons of dumps and tailings being re-milled. Federal government policies and agencies significantly supported mining and milling activities both directly and indirectly into the early 1960’s, Practices encouraged during wartime often contributed to mining’s environmental impact.

SOURCES & REFERENCES

Bird, A llan G. 1986. Silverton Gold, Lakewood, CO. Brown, Robert L. 1984. An Empire of Silver. Denver: Sundance Books. Burbank, W.S. & Luedke, R.G. 1969. Geology cfc Ore Deposits of the Eureka District. Washington, DC,: U.S.G.S. Chase, C.A. 1951 Shenandoah-Dives at its Quarter Century. Denver: Colo. Mng. Assn. 1951 Mining Yearbook. Chase, C.A., & Kentro, D.M. 1938. Tailings Disposal Practice at Shen.-Dives. M ining Congress Journal: March ------. 1942. The Shenandoah-Dives Mine, San Francisco: Mining World Magazine: June issue. Colorado Bureau o f Mines. 1898. Report of the State Bureau of Mines for 1897. Denver. Echo Bay Mines. 1986-1987. Annual Stockholder Reports. Denver. Henderson, C. W. 1926. Mining in Colorado - History, Development & Production. Washington, DC: U.S.G.S. Niebur, JayE. 1986. Arthur Redman Wilfley-Miner, Inventor, & Entrepreneur. Denver: Colo. Historical Society. Ransome, Frederic L. 1901. Economic Geology of the Silverton Quadrangle Colorado ..Washington, DC: U.S.G.S. Rickard, T.A. 1932, A History of American Mining. New York: McGraw Hill. Root, A.P. 1930, Field Notes: Animas River Water Samples. Durango, CO. Slienandoah-Dives Mining Company. 1930-1952. Annual Stockholder Reports. Kansas City, MO. Smith, Duane A, 1987. Mining America - The Industry & the Environment. Lawrence, KS: Univ. o f Kansas. Standard Metals Corporation. 1960-1978, 1984. Annual Stockholder Reports. New York, U.S. Bureau o f Mines. 1955-1963. DMEA Project 2991 Reports: Shenandoah-Dives Mining Co. Denver. U.S. Smelting & Refining. 1930-32. Correspondence: Root & Norton Assayers & Chemists. Durango, CO.

NOTES ON THE CHART OF TOTAL ESTIMATED MINE PRODUCTION

Statistics on total annual mine production were complied by the now defunct U.S. Bureau of Mines and other agencies after 1901, The author is unaware o f any comprehensive published source for this data. Therefore, the total tonnage estimates used in the report and chart of Estimated Tonnage 1871-1991 are based on a variety o f sources and estimates as follows. Out o f the total estimated production o f 17,400,000 tons 14,000,000 tons is firm ly documented with an additional 2,000,000 tons based on high probability estimates for gaps in data for known producing mines. Only 1.4 m illion tons o f the total are based on lower probability estimates.

1. Data from 1871-1900 is recorded in Charles Henderson’s Mining in Colorado (1926) but as annual dollar value o f ores produced, not tons. Tonnage through 1893 is estimated by assuming an average value per ton and calculating accordingly. These tonnages are therefore the least accurate. For 1894-1900 reported ore value per ton for the year 1901 is used to back calculate the tonnage from the dollar figures.

2. From 1901-1923 tonnage cited is from Henderson, 1926.

3. Tonnage for 1924-1926 is estimated from 1927 production quoted in Burbank & Luedke 1969, and adjusted by m ill production rates as quoted in B ird 1986, and Taggart 1927, this being primarily Sunnyside production.

4. Total production for the period 1928-1949 inclusive was complied by Henderson at U.S. Bureau of Mines for use in Chase’s 1952 article on Shenandoah-Dives, but was not broken out as annual figures. Annual figures for Shenandoah-Dives and Highland Mary were obtained from company annual reports, author’s collection. Production figures for the Eureka District, including Sunnyside for 1932-1957 are found in Burbank & Luedke, 1969, These documented sources account fo r 90% o f the 5,268,447 tons compiled by Henderson for the period. The undocumented balance of about 500,000 tons was allocated on an annual basis based on known m ill capacity fo r the Pride o f the West m ill after 1940 and custom m illing capacity at Shenandoah-Dives. The total for the 22-year period is accurate but individual years may be imprecise. 5. Tonnage for 1950-1957 was based on a similar method #4 above using actual Shenandoah-Dives and Burbank & Luedke data w ith estimates added fo r other small operations.

6. For the period 1958-1978 Sunnyside and Shenandoah-Dives’ Silver Lake Unit production plus custom ore are based on annual reports o f Standard Metals Corporation, author’s collection. Estimates for the Pride o f the West m ill (later called the Dixilyn or Howardsville mill) include 20,000 tons from the Oceola and Ransom mines, and Highland Mary dumps and 20,000 tons from the Silver Wing mine 1963-1965.

7. A fter 1978, Sunnyside production is based on tonnage reported in Standard Metals and Echo Bay annual reports fo r 1984-1987. Other years were estimated based on known m ill production rates. Again estimates o f 20,000 tons milled by three operators at the Pride M ill at Howardsville 1979-1981 were added.

AUTHOR INFO RM ATION

W illiam R. Jones is a Professional Registered Assayer and owner o f Root & Norton Laboratories (est. 1908) located in Silverton and Montrose Colorado. Prior to this Jones was an assayer and water analysis technician for Standard Metals Corporation, 1977-1979, He holds a B.A, Degree in Economics and History from Western State College, 1976 and is presently Treasurer o f the San Juan County Historical Society in Silverton,