Brown's Canyon's Fabulous Fluorite Fling
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Brown’s Canyon’s Fabulous Fluorite Fling By Beth Simmons ost people do not have a clue about how the metal bound up in rocks in the ground turns into the steel in their cars. e processing and production of metals requires many secondaryM materials. One of the most essential is uorite, the source of the important element uorine. Fluorine in hydrouoric acid was the main ingredient of uorochlo- rocarbons, the now-outlawed refrigerants. It is an ingredient in insecti- cides, is used in the manufacture of aluminum, and is added to one hun- dred-octane gasoline. Industrial applications such as the open-hearth process of steel making, glass and ceramic enamel manufacturing, and the creation of some medicines all require uorine. In minute quantities, uorine strengthens bones and teeth in organisms that have them. Mineralogy and Geology e mineral uorite, composed of calcium uoride (CaF2), is the primary source of uorine. Other rare minerals that carry some uorine in their matrix include topaz, bertrandite, creedite, and phenakite. Fluo- rite has a hardness of 4 on the Mohs’ hardness scale, crystallizes in the isometric system, and breaks four directions into octahedrons. Its color varies from crystal clear to white, green, blue, purple, yellow, brown, and even brilliant pink. Some uorite crystals from the South Platte district near the old Top-of-the-World campground in the Rampart Range of Colorado were raspberry-red with a sugary coating of white uorite over the top.1 Fluorite can be banded and brous, forming what has been called “ribbon spar” or “bacon spar.” Other growth forms include columnar or ne-grained to microgranular forms, as well as reniform and botryoidal deposits. Like topaz, a uorine-bearing silicate mineral, uorite is very Fabulous Fluorite Fling 45 heavy (dense). Fluorite gave its name to the prop- orine-bearing mineral creedite (Ca3AI2(SO4) . erty of minerals called “uorescence”—glowing (F,OH)10 2H2O), originally named from the de- in the presence of ultraviolet light. Some uorite posit at Wagon Wheel Gap. Fluorite from the “phosphoresces”—glowing aer the black light is Climax Mine at Fremont Pass is some of the n- turned o. Fluorite also exhibits another physi- est from Colorado; purple octahedrons, purple cal property, “thermoluminescence”—glowing dodecahedrons with blue apatite, blue cubes with when heated. Some uorite contains rare-earth rhodochrosite, and green and purple bi-colored elements that exhibit radioactivity.2 cubes all have come from the old molybdenum e term “uorspar” describes a mineral mine. In the North Amethyst vein at Creede, aggregate containing enough uorite to be of green uorite lines vugs and occurs with purple commercial interest. Such a deposit is usually amethyst. Pegmatites of Trout Creek Pass on the classed as strategic or critical because of uo- west side of South Park and of the South Platte rite’s importance to the steel industry. Its im- River District along the Rampart Range produce portance in smelting and rening led the various massive crystalline uorite usually in association “war agencies”—the War Production Board, the with rare-earth minerals.5 Atomic Energy Commission—and the uranium Colorado also has had many sources of u- industry to include studies of uorite resources in orspar—the massive secondary form of uorite. their economic mineral surveys.3 In 1872, mining engineer Robert Old reported Much of the information for this article came “Fluor Spar” in “massive white, green, pink, and from Ralph Van Alstine’s “Geology and Mineral purple metalliferous veins near Bear Creek,” “in Deposits of the Poncha Springs NE uadrangle, the silver mines of Argentine and Grith Dis- Chaee County, Colorado,” a USGS professional tricts,” and “in extensive beds near James Creek paper published in 1969, and Doak Cox’s “Gener- and in small purple and white crystals in Virginia al Features of Colorado Fluorspar Deposits,” pub- Cañon.”6 e earliest uorspar mined in Colo- lished in 1945 in Proceedings of the Colorado Sci- rado came from west of Boulder at Jimtown (now entic Society under the auspices of the USGS and Jamestown), and from pegmatites near Bear Creek funded by the Colorado Metal Mining Fund.4 (now Evergreen) in Jeerson County.7 Nathaniel In Colorado, uorite occurs in “primary” P. Hill and other early smelters used the uorite in pegmatitic ore deposits and in “secondary” hot their processes. spring deposits. Primary crystalline uorite oc- Most Colorado uorspar formed at relatively curs throughout Colorado. At Lake George col- low temperatures under epithermal or perhaps lectors nd crystals up to ten inches square in the partly mesothermal conditions as probably ex- Pikes Peak granite. Sometimes delicate purple ist in hot springs that were not closely related to uorite crystals sit on amazonite or smoky quartz metalliferous deposits. In such deposits, the u- crystals from the mining claims north of Floris- orspar takes a columnar shape or leaves behind sant. e Sweet Home Mine in Park County is ne-grained to microgranular uorite called “sug- famous for its exquisite multi-faced purple uo- ar spar.” Oen reniform or botryoidal masses ag- rite crystals on plates with clear quartz, cherry red glomerate around cores of country rock.8 rhodochrosite, and brown tetrahedrite. Fluorite Almost anywhere there once were hot springs crystals also come from Mt. Antero and Shavano in Colorado there were uorspar mines—at Peak, and other granitic primary deposits in the Wagon Wheel Gap near Creede, in the Brown’s Sawatch Range. Canyon District in Chaee County, at St. Peter’s Colorado molybdenum mines oen pro- Dome along the south side of Pike’s Peak in what duce uorite crystals along with the rare u- is sometimes called the Cheyenne Mountain Dis- 46 2010 Mining History Journal trict, at Poncha Hot Springs in Chaee County, Some partly mineralized faults were more than a and in North Park near Northgate. Mines pro- mile long; ore shoots as much as een hundred duced three grades of uorspar: acid-grade (98 feet long and six feet in width branched o the percent calcium uoride), ceramic-grade (95 per- main veins. Sometimes the vein width exceeded cent calcium uoride), and metallurgical-grade forty feet. e greatest vertical distance through (85 percent calcium uoride with a maximum which any of the veins was exposed was about of 5 percent silicon dioxide).9 is raw uorspar four hundred feet. A pair of north-south veins at required processing. Fluorite mills used a com- the Colorado Fluorspar and American mines and bination of jigs and gravity separators to produce their branches at the Snowake deposit, and at metallurgical-grade concentrates. Some mills the Kramer and other mines on the northern ends used otation processes to produce ceramic-grade of the veins provided the bulk of the ore from the uoride.10 Brown’s Canyon district. is article focuses on uorite deposits in the Most of the uorspar of the Brown’s Canyon Brown’s Canyon area, Chaee County, in central District is white, ne-grained like sugar, and oc- Colorado along the Arkansas Ri zone. e three curs mainly as large irregular masses and bands main uorspar districts in Chaee County were along faults. Surfaces of the masses commonly at Poncha Springs, near the top of Poncha Pass, are botryoidal, mammillary, and locally stalac- and in the Brown’s Canyon District. None of the titic. Some of the ore is nodular and is composed deposits were discovered or developed until the of uorite almost concentrically banded about a 1920s. nucleus of country rock. Some uorite specimens e Brown’s Canyon Fluorite District, about collected at the Snowake deposit glow purple eight miles northwest of Salida, covered an area of about nine square miles and was bounded on the east by the Arkansas River and on the west by U.S. Highway 285, now called the Collegiate Peaks Scenic Byway. Most of the district lies on the west side of the Arkansas River across from the junction of the old Calumet Branch of the Denver and Rio Grande Western Railroad with the main line, the original Hecla Junction was in a region where the maximum relief is only about ve hundred feet. e bedrock of the southern portion of the Brown’s Canyon District is coarsely banded horn- blende gneiss and schist of Precambrian age cut by granite and many pegmatite dikelets and quartz veinlets. ese Precambrian rocks are locally covered by Tertiary volcanic rocks and Tertiary gravels. e uorspar occurs as epithermal s- sure veins along faults in Precambrian granite and metamorphic rock, in Tertiary rhyolite porphyry, Banded uorite om the Last Chance uorite and between rocks of these ages. deposit of the Kramer Mine. Scale in centimeters. In some deposits uorspar replaced fault (From Van Alstine, “Geology and Mineral Depos- breccia extensively enough to form ore bodies. its of the Poncha Springs NE uadrangle,” 1969.) Fabulous Fluorite Fling 47 Chaee County (highlighted) in Colorado. Brown’s Canyon Fluorite District (circled) in Chaee County, Colorado. 48 2010 Mining History Journal Doak Cox’s 1945 map overlain by John Ghist on a 2009 Google Earth satellite image. Mine names and positions obtained om www.Mindat.org. Fluorspar veins appear as solid or dotted lines. Fabulous Fluorite Fling 49 under long-wave ultraviolet light. vein underground through the mill adit. Near e most abundant impurity in the veins of the intersection with the Branch vein where the the Brown’s Canyon District, silica, occurs chiey vein widened out to eight feet thick, the mine ran as grains, veinlets, and in large bands of chalced- southeast through about seventy feet of low-grade ony. Some of this silica is intimately intergrown breccia.