An Occurrence Model for the National Assessment of 

Volcanogenic Beryllium Deposits 

By Nora K. Foley, Robert R. Seal, II, Nadine M. Piatak, and Brianna Hetland

Open-File Report 2010–1195

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 200x

Revised and reprinted: 2010

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Foley, N.K., Seal, R.R., II, Piatak, N.M., and Hetland, B.R., 2010, An occurrence model for the national assessment of 

volcanogenic beryllium deposits: U.S. Geological Survey Open-File Report 2010-1195, 4 p.

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1

An Occurrence Model for the National Assessment of 

Volcanogenic Beryllium Deposits 

By Nora K. Foley, Robert R. Seal, II, Nadine M. Piatak, and Brianna Hetland

The current global and domestic mineral resources of beryllium for industrial uses are dominated 

by ores produced from volcanogenic epithermal beryllium deposits, which are part of a lucrative subset 

of the general class of non-pegmatitic beryllium deposits formed by igneous and hydrothermal 

processes (for example, Barton and Young, 2002). At the present time, beryllium ores produced at the 

Spor Mountain deposit, Juab County, Utah, constitute the principal global and domestic resource of 

beryllium for computer, telecommunications, aerospace, defense, and other industrial applications 

(Jaskula, 2010). The annual worldwide mining production of beryllium (including the United States, 

Brazil, China, Madagascar, Mozambique, and Portugal) currently is estimated to be 140 metric tons; 

over 85 percent is from Spor Mountain (Jaskula, 2010). 

The general occurrence model summarized here is intended to provide a descriptive basis for the 

identification and assessment of undiscovered beryllium deposits of a type and style similar to those 

found at Spor Mountain. The assessment model is restricted in its application in order to provide a 

coherent basis for assessing the probability of the occurrence of similar economic deposits using the 

current U.S. Geological Survey methodology (Singer and Berger, 2007). The model is intended to be 

used to identify tracts of land where volcanogenic epithermal replacement-type beryllium deposits 

hosted by metaluminous to peraluminous rhyolite are most likely to occur. Only a limited number of 

deposits or districts of this type are known, and only the ores of the Spor Mountain district have been 

studied in detail. The model highlights those distinctive aspects and features of volcanogenic epithermal 

beryllium deposits that pertain to the development of assessment criteria and puts forward a baseline 

analysis of the geoenvironmental consequences of mining deposits of this type. Significant papers upon 

which the beryllium deposit assessment model is based include the following: Lindsey and others (1973, 

1975), Lindsey (1977, 1979), Burt and Sheridan (1981), Burt and others (1982), Christensen and others 

(1982, 1984), Ludwig and others (1982), Barton and Young (2002).

Volcanogenic epithermal beryllium deposits can form where the potential exists for the 

interaction of hydrothermal fluids with volcanic rocks of a lithophile-rich composition that contain a 

highly reactive lithic component (for example, carbonate clasts). Volcanic and hypabyssal high-silicacontent, biotite-bearing topaz rhyolite and granite porphyry constitute the most well-recognized igneous 

suites associated with these beryllium deposits. The exemplar setting is an extensional tectonic 

environment (such as the Basin and Range physiographic province) where younger topaz-bearing 

igneous rock sequences overlie older dolomite, quartzite, shale, and limestone sequences. The mined 

deposits and related mineralized rocks at Spor Mountain constitute the only known economic 

occurrence of volcanogenic epithermal beryllium, having proven reserves of 15,900 metric tons of total 
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contained beryllium. The principal commodity produced at mines in the Spor Mountain district is 

beryllium, and it is chiefly derived from the mineral bertrandite, although beryllium-bearing smectites 

(saponite) also occur in association with the deposits. The ores at Spor Mountain reportedly average less 

than 1 percent beryllium oxide and are economically competitive with imported beryl concentrates 

because they are minable by open-pit methods and can be extracted by acid leaching. At Spor Mountain, 

tuffaceous breccias and stratified tuffs that contain the beryllium ore formed as a result of explosive 

iron- and lithophile-rich volcanism that brought carbonate and other lithic fragments to the surface 

through vent structures that cut the underlying dolomitic Paleozoic sequences. The tuffaceous sediments 

and lithic clasts make up volcaniclastic surge deposits. Hydrothermal fluids are thought to have leached 

beryllium and other elements from volcanic glass and redeposited the beryllium as bertrandite upon 

reaction of the hydrothermal fluid with carbonate in lithic-rich sections of tuff. Hydrothermal alteration 

of dolomite clasts formed layered nodules of calcite, opal, and fluorite. At Spor Mountain, the principal 

beryllium ore mineral, bertrandite, occurs as inclusions in fluorite. Distinctive hydrothermal alteration 

assemblages and elemental enrichments in the tuff and surrounding volcanic rocks include regional 

diagenetic clays and potassium feldspar; halos of Nb, Ta, F, Sn, Mo, and Li; intense potassium 

feldspathization; and secondary sericite and lithium-bearing smectite in the immediate vicinity of 

beryllium ore.

The formation of the beryllium deposits is thought to be due to the coincidence of multiple 

factors: (1) a source—high-silica-content, lithophile-rich magmas capable of producing the volcanic and 

hypabyssal high-silica-content biotite-bearing topaz rhyolite and granite porphyry that are included in 

the igneous source rocks; (2) a driver—a process such as magma mixing where hot mafic magma is 

injected into colder felsic magma, setting off vigorous convection in the chamber and leading to 

explosive lithophile-rich volcanism; (3) a site—a host tuff that contains an abundance and distribution 

of dolomite clasts; the carbonate lithic fragments and glassy features provide the porosity and 

permeability, as well as the geochemical and mineralogical components, that are necessary to allow the 

deposits to form; (4) a trap—the confined position of the host tuff between the relatively impermeable 

Paleozoic rocks and the younger topaz-bearing, rhyolitic lava; and (5) a delivery system—convecting 

hydrothermal fluids that are enriched in beryllium, iron, and other lithophile elements and are capable of 

replacing dolomite with calcite, opal, fluorite, and bertrandite.

Other deposit models found in association with the volcanogenic epithermal beryllium deposits 

include volcanogenic uranium, volcanogenic and replacement fluorspar deposits, and fumerolic gemquality beryl deposits. Topaz-bearing rhyolites, like those associated with the volcanogenic epithermal 

beryllium deposits, also are of exploration significance for a range of additional rare metal commodities 

and deposit models, including other volcanogenic deposits; tin, fluorite and silver base-metal districts; 

tungsten belts; topaz-rich porphyry; and molybdenum-tungsten deposits of the Climax and Henderson 

type. 

The environmental geochemistry of beryllium deposits and their associated mine wastes, 

including those at Spor Mountain, have been the subject of several studies (Stonehouse 1986; Deubner 

and others, 2001; Stefaniak and others, 2008). Most of the environmental concerns focus on airborne 

particles associated with ore and metallurgical processing. Only a limited amount of geoenvironmental 

information is available for the Spor Mountain deposit. Ores at Spor Mountain are mined by open-pit 

methods. Because of the low grade of the ore, essentially all of the mined and processed ore becomes 

waste. Studies of beryllium toxicity have shown that neither beryllium sensitization nor chronic 

beryllium disease has been diagnosed in miners at Spor Mountain, which is consistent with the low 

beryllium concentrations in the ore. The key geologic features that may relate directly to the 

geoenvironmental characteristics include the lithophile-rich, high-silica-content rhyolite hosts, 
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associated carbonate rocks, and a sulfide-poor ore assemblage of bertrandite, silica, calcite, fluorite, 

potassium feldspar, and clays. Collectively, these features contribute to a deposit type for which 

minimal environmental concerns are present, such that ecosystem issues related to mining are unlikely 

in the vicinity of the Spor Mountain mine. For example, beryllium concentrations in excess of the 

drinking water standard (4 micrograms per liter) are unlikely because of the arid climate, lack of surface 

water, the low concentrations of beryllium and uranium in the ores, and the low solubility of bertrandite.

Rhyolitic magmas rich in fluorine, beryllium, tin, and other lithophile metals are the favorable 

magmatic source whereas porous carbonate-bearing tuffs and glassy volcaniclastic rocks are the 

favorable hosts for large disseminated beryllium deposits of this type. Deep fractures, such as margin 

faults and caldera ring fractures related to extensional tectonics of the Basin and Range province, may 

be instrumental in tapping the sources of rhyolitic magma and lithophile-rich mineralizing fluids. 

Magma mixing is thought to provide the primary mechanism for explosive volcanism, and nearby 

fluorspar and uranium deposits may indicate the presence of lithophile-rich, mineralizing, hydrothermal 

fluids capable of transporting beryllium. The conversion of dolomite to fluorite results in the release of 

large quantities of carbonate ions and a subsequent increase in the pH of the mineralizing solutions, 

which can be expected to result in widespread and pervasive hydrothermal alteration halos as the more 

alkaline fluids alter the glass and silicates to smectite, sericite, and potassium feldspar. A favorable 

indicator mineral is the presence of abundant early lithium-bearing trioctahedral smectite, which forms 

as magnesium becomes available from dolomite and as lithium is supplied by mineralizing solutions.

Anomalous concentrations of trace elements (including fluorine, beryllium, cesium, lithium, gallium, 

niobium, and yttrium, in combination) in otherwise unaltered volcanic rocks also may indicate 

proximity to volcanogenic beryllium deposits.

References Cited

Barton, M.D., and Young, S., 2002, Non-pegmatitic deposits of beryllium: mineralogy, geology, phase 

equilibria and origin, in Grew, E.S., ed, Beryllium; Mineralogy, petrology and geochemistry: Reviews 

in Mineralogy and Geochemistry, v. 50, p. 591–691.

Burt, D.M., and Sheridan, M.F., 1981, Model for the formation of uranium/lithophile element deposits 

in fluorine-rich volcanic rocks, in Goodell, P.C., and Waters, A.C., ,eds., Uranium in volcanic and 

volcaniclastic rocks: American Association of Petroleum Geologists Studies in Geology 13, p. 99–

109.

Burt, D.M., Bikun, J.V., and Christiansen, E.H., 1982, Topaz rhyolites; Distribution, origin, and 

significance for exploration: Economic Geology, v. 77, p. l818–1836.

Christiansen, E.H., Burt, D.M., and Sheridan, M.F., 1982, The geology and geochemistry of topaz 

rhyolites from the western United States: Geological Society of America Special Paper 205, 82 p.

Christiansen, E.H., Bikun, J.V., Sheridan, M.F., and Burt, D.M., 1984, Geochemical evolution of topaz 

rhyolites from the Thomas Range and Spor Mountain, Utah: American Mineralogist, v. 69, p. 223–

236.

Deubner, D., Kelsh, M., Shum, M., Maier, L., Kent, M., and Lau, E., 2001, Beryllium sensitization, 

chronic beryllium disease, and exposures at a beryllium mining and extraction facility: Applied 

Occupational and Environmental Hygiene, v. 16, no. 5, p. 579–592.

Jaskula, B.W., 2010, Beryllium: U.S. Geological Survey, Mineral Commodity Summaries, p. 28–29.

Lindsey, D.A., 1977, Epithermal beryllium deposits in water-laid tuff, western Utah: Economic 

Geology, v. 72, p. 219–232.
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Lindsey, D.A., 1979, Preliminary report on Tertiary volcanism and uranium mineralization in the 

Thomas Range and northern Drum Mountains, Juab County, Utah,: U.S. Geological Survey Open-File 

Report 79–1076, 101 p.

Lindsey, D.A., Ganow, H., and Mountjoy, W., 1973, Hydrothermal alteration associated with beryllium 

deposits at Spor Mountain, Utah: U.S. Geological Survey Professional Paper 818–A, p. A1–A20.

Lindsey, D.A., Naeser, C.R., and Shawe, D.R., 1975, Age of volcanism and mineralization in the 

Thomas Range, Keg Mountain, and Desert Mountain, Western Utah: U.S Geological Survey Journal 

of Research, v. 3, p. 597-604.

Ludwig, K.R., Lindsey, D.A., Zielinski, R.A., Simmons, K.R., 1982, U-Pb ages of uraniferous opals and 

implications for the history of beryllium, fluorine, and uranium mineralization at Spor Mountain, 

Utah: Earth and Planetary Science Letters, v. 46, p. 221–232.

Singer, D.A., and Berger, V.I., 2007, Deposit models and their application in mineral resource 

assessment, in Briskey, J.A., and Schulz, K.J., eds., Proceedings for a Workshop on Deposit 

Modeling, Mineral Resource Assessment, and Their Role in Sustainable Development: U.S. 

Geological Survey Circular 1294, 143 p.(Also available at http://pubs.usgs.gov/circ/2007/1294/.)

Stefaniak, A.B., Chipera, S.J., Day, G.A., Sabey, P., Dickerson, R.M., Sbarra, D.C., Duling, M.G., 

Lawrence, R.B., Stanton, M.L., and Scripsick, R.C., 2008, Physicochemical characteristics of aerosol 

particles generated during the milling of beryllium silicate ores; Implications for risk assessment: 

Journal of Toxicology and Environmental Health, part A, v. 71, p. 1468–1481.

Stonehouse, J., 1986, Physics and chemistry of beryllium: Journal of Vacuum Science and Technology 

A, v. 4, no. 3, p. 1163–1170.