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Mountain Pass Mine (Mountain Pass deposit; Mountain Pass Mine and mill; Bastnaesite deposit; Bastnäsite deposit; Mountain Pass carbonatite), Mountain Pass, Mountain Pass District, Clark Mts (Clark Mountain Range), San Bernardino Co., California, USA

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Latitude & Longitude (WGS84): 35° 28' 43'' North , 115° 31' 56'' West
Latitude & Longitude (decimal): 35.4786111111, -115.532222222

A baryte-Ce-REE-Au-Ag-Pb deposit/mine located in secs. 12 & 13, T16N, R13E, SBM, 1.5 km (0.9 mile) NE of Mountain Pass (town), immediately N of Interstate highway 15, and about 15 miles W of the Nevada state line, on private (patented) land. It was discovered in 1949. The property is comprised of 6 claims. First production occurred in 1951. The USGS MRDS database stated accuracy for this locality is 10 meters.

Owned & operated by the Molybdenum Corporation of America (MCA)
(100%) (1950-1974); Owned & operated by Molycorp, Inc. (100%) (same company - new name) (1974-1977); owned by the Union Oil of California
(100%) (1977); Operated by Molycorp, Inc. (100%) (1977-2005); Owned & operated by Molycorp Minerals LLC (100%), Englewood, Colorado (1983).

NOTE: The mine ceased active mining in 2002 due to environmental concerns, however the owners, Molycorp Inc., have indicated they plan to return to full production in 2011. Start-up mining activities began in August 2012. In June 2015, however, Molycorp filed for bankruptcy.

Mineral occurrence model information: Model code: 24; USGS model code 10; Deposit model name: Carbonatite. Mineralization involves vein baryte deposits with rare-earth minerals in metamorphic and igneous rocks of Precambrian age. One of the worlds largest lanthanide deposits. There are strong environmental concerns as this mine is situated next to the Mojave National Preserve.

The carbonatite complex (1.4 BP intrusion) is intruded in Precambrian biotite-garnet-sillimanite-hornblende gneisses, biotite granitic gneisses, augen granitic gneisses (Neoproterozoic gneisses) and schists. The carbonatite complex is composed of eight 100 to 2000 meter-long plugs of alkaline intrusive rocks (from shonkinites and syenites to carbonatites) and about 200 dikes of carbonatite in NW-trending rows.

The ore body strikes N10W and dips 40W at a thickness of 75 meters, a depth-to-top of 458 meters (?? - depth-to-bottom ??), a width of 1,590 meters, a length of 750 meters and an area of 1500 HA. Ore body No. 1 is tabular; No. 2 is a fissure vein and No. 3 is a shear zone. The primary mode of origin was magmatic differentiation and the secondary mode was hydrothermal activity. Primary ore control was igneous and the secondary control was fracturing. Wallrock alteration is slight (silicification and carbonitization). Alteration also includes fenitization and hematization. The vein occurs at the contact of a dike and host rock and has an aplite dike hanging wall abnd a gneiss footwall. The dikes trend N30W.

Analytical data results: An ore shoot 100 feet long and 12 to 15 feet thick was said to carry $9.00 (period values) Au per ton.

Analysis of the bastnäsite-(Ce) by Hoffman et al. (1971) have confirmed the presence of plutonium-244 isotope. However, Sakamoto (1974) has suggested, that the source of this exotic isotope may be extraterrestrial.

Workings include surface and underground openings comprised of an open pit with an area of 260 HA and an overall depth of 169.16 meters. Milling method employed was flotation. Water is obtained from wells 10 km E of the mine. Power is supplied by Southern California Edison Company. The access road is paved and labor is available at the site.

An estimated production rate in the 1980's was 1,285 metric tons/day, including 1,155 metric tons/day ore and 130 metric tons/day of dilution material. The production numbers are amount of REE's in the concentrate. This is not the same as the total recovered since there is some loss in processing the concentrate. True production is somewhat less, but loss in processing is not reported.

Reserves and resources: Type: in-situ (estimate year: 1989): Demonstrated: 28,123,000 metric tons of ore; indicated: 28,123,000 metric tons of ore. Total resources: 28,123,000 metric tons of ore. REE (Y group): 8.9 weight percent REE (1989).

Collecting is not allowed.

Mineral List

Mineral list contains entries from the region specified including sub-localities

47 valid minerals. 1 (TL) - type locality of valid minerals.

Localities in this Region


This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Anonymous (1950), Rare earth deposits found in California: California Division of Mines, Mineral Information Service: 3(1): 1.

Anonymous (1950), New products: Mineral Notes & News No. 158: 1-18.

Chesterman, C.W. (1950b), Uranium, thorium and rare-earth elements: California Division Mines Bulletin 156: 361-363.

Olson, Jerry Chipman & William N. Sharp (1951), Geologic setting of the Mountain Pass bastnaesite deposits, San Bernardino County, California: abstract): Geological Society of America Bulletin: 62: 1467.

Pray, Lloyd Charles & William N. Sharp (1951), Bastnaesite discovered near Mountain Pass, California: (abstract): Geological Society of America Bulletin: 62: 1519.

Olson, Jerry Chipman (1952), Preliminary report to accompany the geologic map of the Mountain Pass district, San Bernardino County, California: USGS open file report.

Sharp, W. N. and L. C. Pray (1952), Geologic Map of Bastnaesite Deposits of the Birthday Claims, San Bernardino County, California, U.S. Geological Survey Map MF-4, 1952, Scale 1:600.

Zadra, J.B., et al (1952), Concentration of bastnaesite and other cerium ores: US Bureau of Mines Report of Investigation 4919.

Donnay, Gabrielle & J.D.H. Donnay (1953), The crystallography of bastnaesite, parasite, roetgenite and synchosite: American Mineralogist: 38: 932-965.

Jaffe, H.W., et al (1953), Sahamalite, a new rare earth carbonate mineral, American Mineralogist: 38: 721-754.

Wright, L.A., et al (1953), Mines and mineral resources of San Bernardino County, California: California Journal of Mines and Geology, California Division of Mines (Report 49): 49(1-2): tabulated list No. 189, p. 125.

Hewett. D. F. (1954), History of the Discovery at Mountain Pass, California, In Olson, J. C., and others, Rare-Earth Mineral Deposits of the Mountain Pass District, San Bernardino County, California, USGS Professional Paper 261.

Olson, Jerry Chipman & Lloyd Charles Pray (1954), The Mountain Pass rare earth deposit: California Division Mines & Geology Bulletin 170, chap. VIII: 23-30.

Olson, Jerry Chipman, Shawe, D.R., Pray, L.C., Sharpe, W.N., and Hewlett, D.F. (1954), Geology of the rare-earth deposits of the Mountain Pass district, San Bernardino County California, USGS Professional Paper 261, 75 pp.: 33, 34, 36, 37, 38.

Jaffe, Howard William (1955) Precambrian monazite and zircon from the Mountain Pass rare-earth district, San Bernardino County, California. Geological Society of America Bulletin: 66: 1247-1256.

Glass, Jewell Jeannette, H.T. Evans, Jr., M.K. Carron & Harry Rose, Jr. (1956), Cerite from Mountain Pass, San Bernardino County, California: American Mineralogist: 41: 665.

Hewett, Donnel Foster (1956) Geology and mineral resources of the Ivanpah quadrangle, California and Nevada, USGS Professional Paper 275, 172 pp.

Jaffe, Howard William (1956) Application of the rule of Gladstone and Dale to minerals. American Mineralogist: 41: 764.

Walker, G.W., Lovering, T.G., and Stephens, H.G. (1956), Radioactive Deposits in California: Special Report 49 of the California Division of Mines & Geology: 22, 24.

Gay, Peter (1957), The crystallography of cerite: American Mineralogist: 42: 429-432.

Brobst, D.A. (1958), Barite Resources of the United States, USGS Bulletin 1072-B: 108 (Table 10).

Glass, Jewell Jeannette, H.T. Evans, Jr., M.K. Carron & F.A. Hildebrand (1958), Cerite from Mountain Pass, San Bernardino County, California: American Mineralogist: 43: 460-480.

Ceramic News (1965), New Rare Earth Processing Plant.

Kreusi, P.R. and Duker, G. (1965) Production of rare-earth chloride from bastnaesite. Journal of Metals: 17: 847-849.

Adams, J.W. (1966), Rare earths, California Division Mines & Geology Bulletin 191: 350-355.

Evans, James R. (1966a) California Mountain Pass mine now producing europium oxide. California Division Mines and Geology Mineral Information Service: 18: 23-32.

Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 60, 79, 98, 99, 123, 125, 271, 284, 326, 389.

Weber, F.H., Jr. (1966b), Mineral resources of California: Barite. California Division of Mines and Geology Bulletin: 191: 94-98.

Pings, W.B. (1969) The rare earths today. Colorado School of Mines Mineral Industries Bulletin: 12(2) 1-19.

Hoffman, D.C., Lawrence, F.O., Mewherter, J.L., Rourke, F.M. (1971): Detection of Plutonium-244 in Nature. Nature: 234: 132-134.

Davis, Fenelon Francis and J.R. Evans (1973) Mining activity in California, July 1972 through June 1973. California Division Mines and Geology California Geology: 26: 291-305.

Woodmansee, W.C. (1973) The mineral industry of California: Reprint from 1971. U.S. Bureau of Mines Minerals Yearbook, 50 pp.: 40.

Anonymous (1974), Relationship of Mineralization to Major Structural Features in the Mountain Pass Area, San Bernardino County, California, California Geology, July 1974.

Evans, James R. (1974) Relationship of mineralization to major structural features in the Mountain Pass area, San Bernardino County, California. California Division Mines and Geology, California Geology: 27: 149-157.

Sakamoto, K. (1974): Possible cosmic dust origin of terrestrial plutonium-244. Nature: 248(5444): 130-132.

Lindsey, D. S. (1978), Mountain Pass Mine, Mountain Pass District, San Bernardino County, California, U.S. Bureau of Mines, File Report, September 1978.

Warhol. W. N. (1980), Rare Earths and the Mountain Pass, California Operations. SME-AIME, Pre-Print No. 80-380, October, 1980, 7 p.

Warhol, W. N. (1980), Molycorp's Mountain Pass Operations, In: Fife, D. L., And A. R. Brown, Editors, Geology And Mineral Wealth Of The California Desert. South Coast Geological Society.

Woyski, Margaret S. (1980), Petrology of the Mountain Pass carbonatite complex - A review, in Geology and mineral wealth of the California Desert, Fife, D.L. and Brown A.R., Editors, South Coast Geological Society.

Morrice, E. and M. M. Wong (1982). Flotation of Rare Earths from Bastnaesite Ore. U.S. Bureau of Mines Report of Investigation RI 8689, 13 pp.

Wilson. T. A. (1982), Rare Earths From Lighter Flints To X-Rays. SME-AIME Annual. Meeting Pre-Print No. 82-52, Feb. 1982, 3 p.

Fuerstenau, D. W., Pradip, L. A. Kahn, S. Raghavan (1983), Alternate Reagent Scheme for the Flotation of Mountain Pass Rare-Earth Ore. Pre-Prints - XIV International Processing Conference. Published by Cim, Montreal, Quebec.

Jones, A.P. and Wyllie, P.J. (1983) Low temperature glass quenched from a synthetic rare earth carbonatite: implications for the origin of the Mountain Pass deposit, California. Economic Geology: 78: 1721-1723.

Parkhurst, D. (1983), The Mountain Pass Rare Earth Project. California Mining Journal: March, 1983.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 183, 212, 221, 222, 294, 316-317, 318, 340, 404, 429, 462-463, 479, 486.

Ritchey, J. L. (1983), Mountain Pass Mine, San Bernardino County, California, Bumines MAS Property Evaluation File Report, Sept. 1983, 27 pp.

U.S. Bureau Of Mines (1983), Mineral Commodity Summaries.

De Witt, E., Kwak, L.M., and Zartman, R.E. (1987) U-Th-Pb and 40Ar/39Ar dating of the Mountain Pass carbonatite and alkalic igneous rocks, southeastern California. Geological Society of America, Abstract of Programs: 19: 642.

Burchfiel, B.C., and Davis, G.A. (1988), Mesozoic thrust faults and Cenozoic low-angle normal faults, eastern Spring Mountains Nevada, and Clark Mountains thrust complex, California in This Extended Land: Geological journeys in the southern Basin and Range, Field Trip Guidebook, Geological Society of America, Western Cordilleran Section, Las Vegas, Nevada.

Industrial Minerals (1990), Minerals In The U.S. South-West: Breaking Rocks In The Hot Sun. Industrial Minerals: No. 272, May, 1990.

Haxel, G. (2005) Ultrapotassic rocks, carbonatite and rare earth element deposit, Mountain Pass, southern California. In: Geology and Mineral Resources of the Mojava National Preserve, southern California. USGS Bulletin 2160.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10212814.

Theodore, Ted G. (2007) Geology and Mineral Resources of the East Mojave National Scenic Area, San Bernardino County, California; USGS Bulletin 2160.

Berger, V.I., Singer, D.A., and Orris, G.J. (2009): Carbonatites of the World. Explored Deposits of Nb and REE - Database and Grade and Tonnage Models. USGS Open-File Report 09-1139.

Long, K.R., Van Gosen, B.S., Foley, N.K., and Cordier, Daniel (2010), The Principal Rare Earth Elements Deposits of the United States, A Summary of Domestic Deposits and a Global Perspective; USGS Scientific Investigations Report 2010-5220.

Mariano, A. N. & Mariano, A., Jr. (2012): Rare earth mining and exploration in North America. Elements: 8: 369-376.

U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060710189 & 0060711887.

Mine Safety and Health Administration (MSHA), MSHA file No. 0402542.

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