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he most valuable gem- Gem-quality on quality red beryl comes white devitri- from thc Wah Wah fied rhyolite Mountains of south- matrix. This western Utah (Fig. 1). sample mea- Red beryl occurs as a secondary sures 9 x 26 mm (O.35 x 1 in rhyolite. Market- in.l. (Photo by able crystals from the Wah Wah Sky Hall.) Mountains have been produced from the Mine, operated on a limited scale since 1976 under the ownership of the Harris family of Delta, UT. From 1989 to 1995. oroduction from the mine amounted to more than $3 million with an inventory of several million dollars of unsold gems (Harris, 1995). In 7994, Kennecott Exploration leased the mine and surrounding claims to de- termine reserves and feasibility of gem recovery. and explora- E.H. Christiansen and tion activity are continuing. J.D. Keith are proles-

Previous work on red beryl has s0rs arld T.J. dealt mainly with crystallographic, Thompson is a student, chemical and optical properties of the crystals (Shigley and Foord, Ieparlment of Geohgy,

1984) with only general descriptions Brigham Yrung Univer- of the geology (Ream, 1979). How- sitt Brx 251 I l, Prlvn, ever. the conditions needed for for- mation of red beryl have not been UT 84fi[2 well constrained. It is generally pro- posed that beryl originates by pre- cipitation in fractures and vugs from high-temperature silica rhyolite and andesitic lava flows. gases as they are released from slowly cooled rhyolite Beginning about 23 Ma, the style and composition of lava. Dozens of topaz rhyolite flows and domes, similar volcanism changed to smaller-volume, ash-flow and in composition to the beryl-bearing flow in the Wah Wah dome-forming eruptions of high-silica rhyolite and Mountains. occur across the western United States trachyandesitic lava. These rocks form the Blawn For- (Christiansen et al., 1986). All of these flows devitrified mation of which the beryl-bearing rhyolite is one mem- to form vapor-phase topaz and locally other vapor-phase ber (Best et al., 1987). Abbott et al. (1983) reported a such as , , hematite, pseudo-broo- K-Ar age of 22.1+ 0.8 Ma for this flow. It is probably the kite and . But the occurrence of beryl is rare. oldest topaz rhyolite flow in the Wah Wah Mountains. A Even within the rhyolite flow that hosts the red beryl, the subsequent episode (I2 to 13 Ma) of bimodal productive open pits comprise only a small fraction of magmatism produced the Steamboat Mountain Forma- the surface area of the flow. Apparently, the conditions tion. The rhyolitic part of that is locally topaz-bearing. that favor the formation of red beryl are rarely achieved. Displacement on the late Cenozoic extensional faults that formed the north-trending mountain ranges began Geologic setting about22Ma. The rhyolite flow that hosts the red beryl deposit lies along the eastern flank of the Wah Wah Mountains (Fig. Geology of the Violet Mine 1). Prevolcanic rocks consist of , Paleozoic The rhyolite that hosts the red beryl deposit is part and Mesozoic sedimentary rocks that were folded and of a flow/dome complex that overlies nonwelded tuff of thrust to the east during the Sevier orogeny. Cenozoic cogenetic origin. This rhyolite is exposed over an area of volcanism began about 34 Ma. It consisted mostly of about 9 km2 (3.5 sq miles) (Fig. 1). An unknown addi- larse volume dacitic ash flows and lesser volumes of low- tional portion of the rhyolite is concealed beneath

MfNtNG ENGTNEERTNG r FEBRUARY 1997 37 Fte I

TXPTANAIION Map of rhyolite lava flow Xat. liavfr o[ B{mstm the that ReswF F6 {12-l? }.1a, hosts red beryl in the Wah Wah = lo$"z ffxI red be.yl rhyoltte Mountains. The map shows the loca- I d ,lb*n tn ( ?$ ilal tion of faults, argillic alteration and Iufl mmls of Bf*n erosional lineaments. = f qwtffi (20-22 |{al ff hdela{ l4ocere Iraben

r>}ergte lault distinctive elemental compositions gr*e aflt drp of 1stBry lE(klql detlGrts are present in the complex. Appar- ently, several magmas were at least Str&e rxl dip of tert@y compacton fo[at0n partially mixed during eruption and Irfe,red dflectron ol fh&'al emplacement. lranslnrt p(of to eml)lacement of red beryl rhyolte Within the Violet Mine, red beryl crystals occur as well-formed crystals up to several centimeters long. Euhedral beryl crystals are mostly embedded in soft . But they may be tightly encased by dense, devitrified rhyolite. This indi- younger mafic lavas and sediments. cates crystal growth by replacement of rhyolite rather The authors'work suggests that the red beryl flow than open-space filling. Beryl tends to form euhedral occupies a northeast-trending graben (Keith et a1.,1994). crystals by metasomatic replacement in other settings as Fluvial sediments are present beneath and above por- well (Beus, 1983). Unlike other localities, the red beryl is tions of the red beryl rhyolite. Streams may have emp- not found in lithophysal cavities. Here, beryl crystals tied into the graben. Compaction foliations of appear to occur exclusively along, or adjacent to, underlying ash flow tuff units dip toward the inferred subvertical fractures in the rhyolite. Not all fractures, graben. The graben is also parallel to the dominant ori- nor all portions of a single , contain beryl. Often, entation of faults and dikes of Blawn age (Fig. 1). the productive zone of any single fracture is less than 3 to The rhyolite has a mineralogy and composition simi- 4 m (10 to 13 ft) high and 30 to 60 m (100 to 200 ft) long. lar to most other topaz rhyolites. It is enriched in incom- The fracture orientations cluster in two groups with azi- patible elements like Rb, Nb, Y and Be (about 20 ppm) muths of about 65" and 140'. Fractures are parallel and and depleted in compatible elements like Ti, Sr and Ba. perpendicular to the inferred trend of the graben. They For example, CaO concentrations (<0.01 to 0.52o/") are may have formed as the flow was channelized by the gra- low, even lower than most topaz rhyolites. Phenocrysts ben. These shrinkage cracks formed during cooling. of , , sanidine and sparse are They may have served as the roots of fumaroles that al- present. Both crystal-poor (about 5% phenocrysts) and lowed collection and transport of exsolved vapors and crystal-rich (about 15% phenocrysts) rhyolite make up influent surface water. the red beryl flow. In some areas, the two kinds of lava The productive fractures contain vapor-phase miner- occur as distinct, intermixed portions of strongly flow- als such as bixbyite, tridymite, cristobalite and rare topaz. laminated or brecciated rock. Moreover. lavas with two Most have amorphous silica and clay. Fracture-hosted clays are mostly kaolin with trace amounts of smectite or a more nlixed-layer clay (about 20% illite and about 80% smectite). Both types of bulk clay contain traces of R . Some red beryl crystals oc- cur along irregular planes. These appear to have been once open frac- tures that were sealed by deposition of tridymite or cristobalilte but clay is not obvious. Bixbyite and Mn-he- matite also occur along these sealed fractures. Most of the beryl-bearing frac- tures contain abundant kaolin. However, it is unlikely that beryl

Rex Harris, owner of the Violet Mine, works a fracture. Red beryl occurs along -stained fractures that are commonly argillized. lt is embedded in devitrified rhyolite.

38 FEBRUARy 1997 x MINING ENGINEERTNG FTG.2 .;r;;;:1:ji;.';11;,. .,:.:,,,r.,1.;,-,;;r:i;tii::jl,:.-'i};,:Ii-,, '.'i.--:1, ..,+, ;,:''i:,..,.1f,.r:i.1,: ru,i.l:j:d:;e.'i Schematic of a cross section showing the sequential de- A Incursion of low- velopment of red beryl along a shrinkage lracture within I water- rich f luid flow-foliated rhyolite. Step A At shallow depths within I Y the devitrifying rhyolite llow, exsolved- Be fluoride com- --;***-- plexes escape without reacting with to produce r F racture-peposited beryl. 0ther vapor-phase mineral may be deposited in or bi xby ite, hemati te, near the fracture at this time. ,>- $4n- ,. * topaz, +i SiO2 polymor

and kaolin formed concurrently as an equilibrium as- Cl osely-spaced shr inkagej cr acks semblage. Barton (1986) noted that beryl often alters to ',! Exsolved vapors form kaolinite but they form together only at low activi- j ( ties of beryl (along with pegmatitic that are alkali- Devi tr i fi ng presence rich). The of abundant kaolin along many J rhyolite fractures indicates the eventual establishment of a low { pH, water-rich environment after beryl formation. \ Some details of the mineralization sequence can be tcrr Negligible gradient in T, established using cross-cutting and inclusion relation- pH, and fH2O ships. Bixbyite and topaz were among the earliest vapor- phase minerals. They appear to have cocrystallized with K-feldspar and silica minerals during primary devitrifica- tion. Beryl is distinctly later and contains abundant in- lying mafic lavas. However, a significant amount of ero- clusions of quartz, K-feldspar, bixbyite and Mn-hematite, sion may have occur,red before the eruption of the mafic often with textures indicating replacement (Aurisicchio lavas, considering the 9 million years that elapsed. The et al., 1990). In addition, bixbyite is one of the best indi- nature of the flow foliation may also give some indica- cators of potential beryl-bearing fractures. The clays tion of depth. In and near the main pit. the flow foliation found along most of the fractures are not found within strikes northeast and dips 25" to 40 northwest. Moder- the red beryl crystals, but as coatings, suggesting that the ately inclined flow foliation is common at medial levels clays formed last, perhaps at much lower temperatures within rhyolite flows. It is found beneath a more steeply than the beryl. inclined and brecciated upper zone (Burt and Sheridan, New electron microprobe analyses of Wah Wah 1987). The foliation in the mine is defined by alternating beryl - (K,Na)028Be3A, r, (Fe,Mn)0.25(Si6O,8) re- gray (less devitrified) and white (more devitrified) lay- veal that many of the unusual major and trace element- ers. The more devitrified layers were likely the source characteristics may be related to the replacement reac- and the transport medium for vapors from which beryl tion by which it formed and to the high fO2 that pre- and other vapor-phase minerals crystallized. vailed during devitrification and vapor-phase alteration. The most obvious zonation of alteration minerals is Red beryl contains significant amounts of transition ele- in the abundance of Fe-staining (/) ments that substitute for Al in the octahedral site of the along fractures. Fe-staining is negligible in the upper 120 beryl structure. In many other beryls, cations that substi- m (395 ft) of the rhyolite. It is conspicuous at the level of tute for Al have +2 charges. The charge deficiency is red beryl formation and increases in abundance down- compensated for by entry of +l alkalies into channel ward. Much of the Fe-staining along the fractures may sites. have been derived from destruction of bixbvite and Mn- However, because of high fugacities, most of hematite during or reaction with cool ground the Fe and Mn in red beryl is probably +3. This elimi- water. Topaz is dominantly present above the red beryl. nates the need for alkalis in channel sites for charse bal- It formed in lithophysal vugs and along fractures that ance. It also explains why red beryl lack any clay alteration. is poor in alkalies compared with Red beryl (1.OO calatsl from the Keith et al. (1994) concluded most other beryl varieties. This is es- Violet Mine with brilliant round cut that the main geochemical changes pecially compelling considering that by Tina Nelson- lt is valued at in the rhyolites $ts,Ooo/. (Photo by Sky Hall.) that accompanied the beryl grew in an alkali-rich envi- the formation of beryl included sub- ronment. stantial depletions of Na and F and Fluid inclusions in the beryl are enrichment of Sr, Y, Sc and loss on one-phase and filled with vapor ignition at 1,000' C (1,830' F), a showing that crystallization was measure of HrO content. There are pneumatolytic rather than hydro- only a few significant differences thermal (Roedder and Stalder, between beryl-bearing and topaz- 1986). Similar inclusions are found bearing samples. These include in topaz from lithophysalcavities in marked enrichments in Be. Ba, CaO the same flow. and MgO in the beryl-containing Depth within a lava flow may be rhyolite. These changes are prob- an important control on beryl for- ably associated with the formation mation. At the Violet Mine, beryl of smectite-rich clays and beryl and occurs about 170 m (560 ft) below the destruction of feldspar in the the extrapolated contact with over- beryl-bearing samples.

MTNING ENGTNEERING x FEBRUARY 1997 39 The compositions of vrrro-phyres to the flow suggest that the center of a flow should cool more slowly and be that before beryl formed, the lavas were modified by subject to more pervasive devitrification and the correla- simple devitrification and degassing. Crystallization of tive release of halogens and complexed metals, such as glass after eruption was apparently associated with sub- Be (Fig.2). stantial losses of several volatile elements including Cl Red beryl must have grown at temperatures below (90%) and F (50o/o to95"/"), and magmatic water as well. magmatic values (about 650" C or 1,200o F), but above The loss of water cannot be evaluated quantitatively be- the temperature of kaolin development (200" to 300' C cause water increases as glassy rocks hydrate by the ad- or 390' to 570' F). Apparently, surface water had access dition of meteoric water. to the interior of the rhyolite flow and a water- and oxy- Coincident with the release of volatiles, other ele- gen-rich vapor permeated shrinkage fractures that also ments could be transported complexed in the vapor. For served as fumarolic root zones. example, if a vitrophyre present at the base of the flow Simultaneously, a magmatic vapor - dominantly exhibits magmatic Be concentrations, then devitrified HrO and CO, with Cl, F and complexed metals - was samples have lost 20"/o to 650/" of their original Be con- released from the devitrifying lava and moved along tent. flow foliation. Wood 0,992) found that fluoride com- plexes are the most likely transporting ligands for Be in Genetic model topaz-bearing assemblages. Additionally, near neutral A genetic model for the formation of red beryl at the pH, with high K in activities (K-feldspar stable) and very Violet Mine can be constructed based on the observa- low Ca activities, are also required to allow signifi- tions described above and limited experimental work. cant Be transport as fluoride complexes. Crustal extension and the eruption of distinctive to- The activities of K and F species in the vapors re- paz rhyolites are obvious prerequisites to the formation leased during devitrification of rhyolite were buffered by of the beryl. Eruptions of topaz rhyolites in the eastern the presence of early formed K-feldspar and topaz. The Great Basin from 18 to22Ma mark the inception of ex- CaO content of the rhyolite in and surrounding the Vio- tensional tectonism in the region. The productive flow let Mine is particularly low (<0.01% to 0.18%). Even probably lies in a northeast-trending graben formed dur- this may have been introduced by surface or meteoric ing this episode of extension. The location of the flow water during formation of late smectite. within a valley or graben may have allowed greater than Low Ca activities in the host fluid and rock should normal interaction of the hot flow with surface waters. allow F to complex and transport Be, rather than form This enhanced the formation of beryl, kaolin and fluorite (CaFr). Low Ca may be more important to beryl smectite. Other beryl-absent ropaz rhyolite flows in the formation than unusually high Be or F concentrations. southern Wah Wah Mountains lack evidence for substan- Locatly, and probably in response to cooling, silica min- tial reaction with surface waters. erals, topaz, bixbyite and hematite crystallized from The fracturing and flow foliation of the host rhyolite these vapors, lining the foliation planes, vugs and indicates that the red beryl formed in the medial zone of lithophysae (Fig. 3). Eventually, some of the magmatic the flow and away from the vent. It may be important vapor also encountered the subvertical shrinkage frac- tures. The Be-bearing magmatic vapors reacted with sur- face-water vapor and fracture-hosted minerals to produce red beryl. In a discussion ofbertrandite and phenakite deposi- tion, Wood (1992) proposed that Be-bearing complexes can be broken by lowering the fluoride activity (due to the presence of a calcareous lithology or fluid to produce fluorite), a temperature decrease or a decrease in K-ion activity. The last two changes would be produced if me- teoric water mixed with magmatic vapor along the verti- cal fractures in the rhyolite lava flow. A hypothetical tncw of low- clensity B I sion reaction that produces the beryl composition water-rich fluid balanced I found at the Violet claims illustrates the reaction be- v tween water and fluoride carried in vapors and i preexisting bixbyite, feldspar and quartz to form beryl, hydrofluoric acid and soluble alkali fluorides:

: : Nucleati0n and 25.5H2O + 1 .5(Fe,Mn)rO. + 21 (K,Na)AlSi3O8 + 9SiO, .--" gr0wth of red lxryl Zone of + 36B-eF, 12(K,Na)n higher,fH20 rrBe3Al, rr(Fe,Mn)0.25(Si6O1s) i +51HF + 21(K,Na)-> F 1 and fo2 ; Exsolved rirpor. During formation of Be fluoride complexes by devit- with near ineutr al pH rhyolite I rification, water fugacites within nonfractured

1 were probably relatively low. Consequently, any in- ,-..._-.._l I crease in HrO activity as vapor encountered open frac- +-- Decreasing T, P, and pH tures would push the reaction to the right. Experimental - llnt work on the stability of beryllium minerals indicates that the stability of beryl is greatly expanded (relative to other beryllium minerals) in the presence of water (or

40 FEBRUARY 1997 T high fluid pressures) and by alkali contarnrng solutions. FIG.4 Higher activities of Mn, Fe and alkalies may have al- ,:ri:iri:,,11ii1{F4.i:.1+sii1, lowed the stability field of beryl to expand because of Step C. Temperature and pH continue to decrease along solution (Barton, 1986). the fracture while lllr0 increases until beryl and Some fractures were sealed after beryl formation by become unstable and kaolinite is produced. Some beryl ubiquitous SiO, polymorphs. They contain only beryl, crystals may become etched by this reaction. At very low bixbyite, Iopaz (?) and Mn-hematite. Most of the beryl- temperatures, mixed-layer smectate/i llite clay is formed. bearing fractures, however, also contain abundant kaolin Some Mn-hematite may be converted to goethite/limonite and mixed-layer smectite-illite clays. The eventual for- during clay formation. mation of a liquid aqueous phase in response to cooling may have terminated formation of beryl and initiated clay formation along most fractures (Fig.4). The argillic alteration is overprinted on the higher temperature Higher- density (boiling?) beryl-containing assemblage. water- rich fluid Moreover, some clay-hosted beryl crystals have etched surfaces. This implies that they began to react to form kaolin, the most common alteration product of beryl (Barton,1986). The acidic water that formed ka- olin-filled fractures also may have converted much of the early-formed specular hematite to limonite or goethite that prominently stain the clay-filled fractures. J,pception 6f weak clay This model for red beryl formation suggests that the alterationjin host r ock best areas to prospect for deposits may be characterized by some or all of the following:

. High silica rhyolitic lava with vapor phase topaz. Such lavas can be identified geochemically by high concentrations of F (>0.2%) and high concentra- {at lower T) tions of incompatible elements (Rb >300 ppm; Nb >40 ppm, Be >15 ppm). Moreover, those lava flows that have topaz probably have devitrified suffi- ciently to release Be from glass (or magma) to a va- and growth of red beryl from Utah," Rendiconti Fisiche Accademia por phase. They also have enough fluorine to Lincei ser. 9, Vol. 1, No. 4, pp.393-404. transport Be as fluoride complexes. Barton, M.D., 1986, "Phase equilibria and thermodynamic prop- o Very low (<0.5 %) whole-rock CaO concentrations. erties of minerals in the BeO-A1rO3-SiO2-H2O (BASH) system, with Low CaO may allow extended transport of Be fluo- petrologic applications,".4 merican Mineralogist ,Vol. 71, pp. 277-300. ride complexes rather than promoting precipitation Best, M.G., et al.,1987, "Miocene magmatism and tectonism in of fluorite (CaFr). and near the southern Wah Wah Mountains, southwestern Utah," US o [Jnbrecciated portions of rhyolite flow with coher- Geological Survey Professional Paper 1433-8, pp. 29-47. ent flow foliation that is moderately inclined (25" to Beus, A., 1983, "On the possible mechanism of formation of 40'). These features indicate that a site is distant euhedral crystals in metasomatic processes," Bulletin of Mineralogy, from a vent and at moderate depths within the flow Vol. 106,pp. 477 -415. - perhaps an indication of the modest depth that Burt, D.M. and Sheridan, M.F., 1987, "Types of mineralization appears to be critical for beryl formation. related to fluorine-rich silicic lava flows and domes." Geological Soci- . Moderate, but persistent, Fe-staining along fractures ety ofAmerica Special Paper 212,pp.103-109. along with trace amounts of vapor-phase bixbyite Christiansen, E'.H., Sheridan, M.F. and Burt, D.M., 1986, "The and Mn-hematite. Early formed Fe and Mn geology and geochemistry of Cenozoic topaz rhyolites from the west- may react with Be fluoride vapors to form beryl. ern United States," Geological Society of America Special Paper 205, Substitution of Fe and Mn for Be and Al may en- 82 pp. hance beryl stability. Keith, J.D., Christiansen, E.H. and Tingey, D.G., 1994. "Geologi- . Clay-filled fractures that contain a combination of cal and chemical conditions of formation of red beryl, Wah Wah kaolin and mixed-layer illite-smectite. These miner- Mountains, Utah," Utah Geological Association Publication 23, pp. als may be a lower temperature expression of a pro- 155-169. ductive fracture. I Ream, L.R.,1979 "The Thomas Range,WahWah Mountains, and vicinity, western Utah," Mineralogical Record, Vol. 10, pp. 261-278. Acknowledgments Roedder, E. and Stalder H. A., t986, "Pneumatolysis and fluid The permission of the Harris family to study the Vio- inclusion evidence for crystal growth from a vapor," Memoirs of the let Mine is appreciated. D.G.Tingey helped with the ana- Geological Society of India,Yol. ll, pp. lfz. lytical work. Shigley, J.E. and Foord, E.E., 1984, "Gem-quality red beryl from the Wah Wah Mountains, Utah," Gems and ,Yol.20,pp.209- References 221. Abbott, J.T.. Best, M.G. and Morris, H.T., 1983, Geologic map of Wood, S.A., 1992, "Theoretical prediction of speciation and solu- the Pine Grove-Blawn Mountain area, Beaver County, UT, US Geo- bility of beryllium in hydrothermal solution to 300' C at saturated logical Survey Miscellaneous Investigations Series Map 1-1479. vapor pressure: Application to bertrandite/phenakite deposits," Aurisicchio, C., Fioravanti, G. and Grubessi, O., 1990, "Genesis Geology Reviews, Vol. 7, pp. 249-278.

MINING ENGINEERING T FEBRUARY 1997 41 Mininglawupdate

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ince its passage, the Mining Law of 1872 has been modified several Many reforms are being sug- times to meet the changing needs of America's society and economy. gested to the Despite the fact that it continues to provide an effective framework Mining Law of for a robust US exploration and mining industry, the mining law con- 1872. The re- tinues to be criticized in some quarters as outdated. forms would mines Pressure reform the Mining Law of 1872 has reached new levels in impact to such as Barrick recent years. Many proposals for reform of the law have been introduced 's Betze- during the 1990s. None, though, have been enacted. The issue will not likely Post pit in Ne- disappear and is certain to be raised during the 105th Congress. vada, shown (Photo To provide a better understanding of the status of current congressional here. in courtesy of reform proposals, this article presents an overview of the major moments Barrick Gold.l the history of mining laws in the western United States from the days be- fore the 1872 mining law and the days following its promulgation,- to the cur- rent dilemma over mining law reform. The future of the mining law is assessed as are the interests at stake for the modern mining industry.

Stanley [lempsey, Mining before 1872 No discussion of the Mining Law of 1872 is complete without some his- member SM[, is thait torical background to provide an understanding of the origins of this unique II|ar| a[|d [hief exe[ulille law. There was plenty of mining activity on the public lands before the min- policy was to allow all nflicer il flryal Grld ing law was enacted. At first, the federal government's miners to work freely on the public lands and to resolve disputes among l6E0lltlynkrnp St, Inc, themselves. Suite I 000, 0enver [0 In this "hands off" environment, miners operated according to laws they

00202-t I 32 promulgated. These were based on previous experiences in Europe and Mexico. These "frontier codes" of groups of individual miners took the form M 42 FEBRUARY 1997 I MINING ENGINEERING