The Mountain Pass Rare Earth Mine is an open-pit mine of rare-earth elements (REEs) on the south flank of the Clark Mountain Range, just north of the unincorporated community of Mountain Pass, California, United States. The mine, owned by Molycorp Inc., once supplied most of the world's rare-earth elements. Molycorp is in bankruptcy proceedings as of Jan 2016.
Video Mountain Pass rare earth mine
GeologyEdit
The Mountain Pass deposit is in a 1.4 billion year old Precambrian carbonatite intruded into gneiss, and contains 8% to 12% rare-earth oxides, mostly contained in the mineral bastnäsite. Gangue minerals include calcite, barite, and dolomite. It is regarded as a world-class rare-earth mineral deposit. The metals that can be extracted from it include:
- Cerium
- Lanthanum
- Neodymium
- Europium
Known remaining reserves were estimated to exceed 20 million tons of ore as of 2008, using a 5% cutoff grade, and averaging 8.9% rare-earth oxides.
Maps Mountain Pass rare earth mine
Ore processingEdit
The bastnäsite ore was finely ground, and subjected to froth flotation to separate the bulk of the bastnäsite from the accompanying barite, calcite, and dolomite. Marketable products include each of the major intermediates of the ore dressing process: flotation concentrate, acid-washed flotation concentrate, calcined acid-washed bastnäsite, and finally a cerium concentrate, which was the insoluble residue left after the calcined bastnäsite had been leached with hydrochloric acid.
The lanthanides that dissolved as a result of the acid treatment were subjected to solvent extraction, to capture the europium, and purify the other individual components of the ore. A further product included a lanthanide mix, depleted of much of the cerium, and essentially all of samarium and heavier lanthanides. The calcination of bastnäsite had driven off the carbon dioxide content, leaving an oxide-fluoride, in which the cerium content had become oxidized to the less-basic quadrivalent state. However, the high temperature of the calcination gave less-reactive oxide, and the use of hydrochloric acid, which can cause reduction of quadrivalent cerium, led to an incomplete separation of cerium and the trivalent lanthanides.
HistoryEdit
The Mountain Pass deposit was discovered by a uranium prospector in 1949, who noticed the anomalously high radioactivity. The Molybdenum Corporation of America bought the mining claims, and small-scale production began in 1952. Production expanded greatly in the 1960s, to supply demand for europium used in color television screens.
The deposit was mined in a larger scale between 1965 and 1995. During this time the mine supplied most of the worldwide rare-earth metals consumption. The Molybdenum Corporation of America changed its name to Molycorp in 1974. The corporation was acquired by Union Oil in 1977, which in turn became part of Chevron Corporation in 2005.
The mine closed in 2002, in response to both environmental restrictions and lower prices for REEs. The mine has been mostly inactive since 2002, though processing of previously mined ore continues at the site.
In 2008, Chevron sold the mine to privately held Molycorp Minerals LLC, a company formed to revive the Mountain Pass mine. On July 29, 2010, Molycorp, Inc. became a publicly traded firm by selling 28,125,000 shares at $14 in its IPO. The shares trade under the ticker symbol MCP on the NYSE.
On June 25, 2015, Molycorp filed for Chapter 11 bankruptcy. The company's shares were removed from the NYSE and as of January 2016 are traded OTC under the symbol MCPIQ. At the time of the bankruptcy, Molycorp had outstanding bonds in the amount of $US 1.4 billion.
On July 10, 2017, MP Mine Operations LLC purchased the Mountain Pass mine out of bankruptcy.
Environmental impactEdit
In 1998, chemical processing at the mine was stopped after a series of wastewater leaks. Hundreds of thousands of gallons of water carrying radioactive waste spilled into and around Ivanpah Dry Lake.
In the 1980s, the company began piping wastewater as far as 14 miles to evaporation ponds on or near Ivanpah Dry Lake, east of Interstate 15 near Nevada. This pipeline repeatedly ruptured during cleaning operations to remove mineral deposits called scale. The scale is radioactive because of the presence of thorium and radium, which occur naturally in the rare-earth ore. A federal investigation later found that some 60 spills--some unreported--occurred between 1984 and 1998, when the pipeline was shut down. In all, about 600,000 gallons of radioactive and other hazardous waste flowed onto the desert floor, according to federal authorities. By the end of the 1990s, Unocal was served with a cleanup order and a San Bernardino County district attorney's lawsuit. The company paid more than $1.4 million in fines and settlements. After preparing a cleanup plan and completing an extensive environmental study, Unocal in 2004 won approval of a county permit that allowed the mine to operate for another 30 years. The mine also passed a key county inspection in 2007.
Current activityEdit
The mine, once the world's dominant producer of rare-earth elements, was closed in large part due to competition from REEs imported from China, which in 2009 supplied more than 96% of the world's REEs. Since 2007 China has restricted exports of REEs and imposed export tariffs, both to conserve resources and to give preference to Chinese manufacturers. Some outside China are concerned that because rare earths are essential to some high-tech, renewable-energy, and defense-related technologies, the world should not be reliant on a single source. On September 22, 2010, China quietly enacted a ban on exports of rare earths to Japan, a move suspected to be in retaliation for the Japanese arrest of a Chinese trawler captain in a territorial dispute. Because Japan and China are the only current sources for rare-earth magnetic material used in the US, a permanent disruption of Chinese rare-earth supply to Japan would leave China as the sole source. Jeff Green, a rare-earth lobbyist, said, "We are going to be 100 percent reliant on the Chinese to make the components for the defense supply chain." The House Committee on Science and Technology scheduled on September 23, 2010, the review of a detailed bill to subsidize the revival of the American rare-earths industry, including the reopening of the Mountain Pass mine.
The mine was once owned by Molycorp Minerals LLC, a subsidiary of Molycorp Inc..[13] Molycorp planned to invest $500 million to reopen and expand the mine.[14]The money was raised through an initial public offering of stock in Molycorp Inc.[15] Full mining operations were planned to resume by the second half of 2011 as a result of increased demand for rare-earth metals.[16] In December 2010, Molycorp announced that it had secured all the environmental permits needed to begin construction of a new ore processing plant at the mine; construction would begin in January 2011, and was expected to be completed by the end of 2012.[17] The company announced its resumption of operations on a start-up basis at the Mountain Pass mine on August 27, 2012.[18] As of 2015, the plant was in full production.[19]Molycorp filed for bankruptcy in June 2015. In August 2015, it was reported that the mines was to be shutdown.[20] On August 31, 2016 Molycorp Inc. emerged from chapter 11 bankruptcy as Neo Performance Materials, leaving behind the mine as Molycorp Minerals LLC in its own separate chapter 11 bankruptcy.
In July 2017, MP Mine Operations LLC ("MPMO") purchased Mountain Pass. MPMO is currently working to recommence operations at Mountain Pass.
ReferencesEdit
Other referencesEdit
- Castor, Stephen B. (2008). "Rare Earth Deposits of North America". Resource Geology. 58 (4): 337. doi:10.1111/j.1751-3928.2008.00068.x.
- Jones, Adrian P; Wall, Frances; Terry Williams, C (1996). "origin and ore deposits". Rare earth minerals: chemistry. Springer. p. 105. ISBN 978-0-412-61030-1.
- Jaffe, Howard W. (1955). "Precambrian Monazite and Zircon from the Mountain Pass Rare-Earth District, San Bernardino County, California". Geological Society of America Bulletin. 66 (10): 1247-56. Bibcode:1955GSAB...66.1247J. doi:10.1130/0016-7606(1955)66[1247:PMAZFT]2.0.CO;2. ISSN 0016-7606.
- Kay, Robert W; Gast, Paul W (1973). "The Rare Earth Content and Origin of Alkali-Rich Basalts". The Journal of Geology. JSTOR. 81 (6): 653-682. Bibcode:1973JG.....81..653K. doi:10.1086/627919. JSTOR 30058994.
- Olmez, Ilhan; Sholkovitz, Edward R.; Hermann, Diane; Eganhouse, Robert P. (1991). "Rare earth elements in sediments off Southern California: a new anthropogenic indicator". Environmental Science & Technology. 25 (2): 310. Bibcode:1991EnST...25..310O. doi:10.1021/es00014a015.
- Olson, J. C.; Shawe, D. R.; Pray, L. C.; Sharp, W. N. (1954). "Rare-Earth Mineral Deposits of the Mountain Pass District, San Bernardino County, California". Science. 119 (3088): 325-6. Bibcode:1954Sci...119..325O. doi:10.1126/science.119.3088.325. PMID 17754332.
External linksEdit
- Molycorp Minerals official website
Source of article : Wikipedia
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