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
|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 ListMineral list contains entries from the region specified including sub-localities
44 valid minerals. 1 (TL) - type locality of valid minerals.
This information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This data will improve over time as more accurate maps and data sets are added.
|Miocene - Paleoproterozoic5.333 - 2500 Ma||Precambrian rocks, undivided, unit 2 (Mojave Desert and Transverse Ranges)|
|Permian - Carboniferous252.17 - 358.9 Ma||Carboniferous-Permian sedimentary rocks|
|Paleoproterozoic1600 - 2500 Ma||Paleoproterozoic metamorphic and undivided crystalline: sedimentary and volcanic gneiss|
Metamorphic and undivided crystalline: sedimentary and volcanic gneiss
References for regional geology:
Data provided by Macrostrat.org
Garrity, C.P., and Soller, D.R.,. Database of the Geologic Map of North America: adapted from the map by J.C. Reed, Jr. and others (2005). U.S. Geological Survey Data Series 424 .
USGS compilers. State geologic map data. State Maps.
Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d.
Localities in this Region
- San Bernardino Co.
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