Mountain Pass rare earth mine
Encyclopedia
The Mountain Pass rare earth mine is an open-pit mine of rare earth element
s (REEs) on the south flank of the Clark Mountain Range
and 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. The facility is currently undergoing expansion and modernization, and expected to be back up to full production in 2011.
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:
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.
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.
The deposit was mined in a larger scale between 1965 and 1995. During this time the mine supplied most of the world wide 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.
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.
The mine is owned by Molycorp Minerals LLC, which is a subsidiary of Molycorp Inc.. Molycorp plans to invest $500 million to reopen and expand the mine. The money was raised through an initial public offering of stock in Molycorp Inc. Current plans are for full mining operations to resume by the second half of 2011 as a result of increased demand for rare earth metals. In December 2010, Molycorp announced that it secured all the environmental permits needed to begin construction of a new ore processing plant at the mine; construction will begin in January 2011, and is expected to be completed by the end of 2012.
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
s (REEs) on the south flank of the Clark Mountain Range
Clark Mountain Range
The Clark Mountain Range is located in southeastern California, north of Interstate 15 and the community of Mountain Pass. The range stretches approximately 15 miles in a southwest-northeasterly direction, beginning in the Mojave National Preserve, and ending near Stateline Pass, about one mile ...
and just north of the unincorporated community of Mountain Pass, California
Mountain Pass, California
Mountain Pass is an unincorporated community in San Bernardino County, California, United States. It is situated on Interstate 15 in the southeast mountainous desert region of the state approximately from the Nevada border at an elevation of - the highest point along I-15 between California and...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The mine, owned by Molycorp Inc., once supplied most of the world's rare earth elements. The facility is currently undergoing expansion and modernization, and expected to be back up to full production in 2011.
Geology
The Mountain Pass deposit is in a 1.4 billion year old PrecambrianPrecambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
carbonatite
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
intruded into gneiss
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
, and contains 8% to 12% rare earth oxides, mostly contained in the mineral bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
. Gangue
Gangue
In mining, gangue is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit. The separation of mineral from gangue is known as mineral processing, mineral dressing or ore dressing and it is a necessary and often significant aspect of mining...
minerals include calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, barite
Barite
Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...
, and dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
. It is regarded as a world-class rare-earth mineral deposit. The metals that can be extracted from it include:
- CeriumCeriumCerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...
- LanthanumLanthanumLanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
- NeodymiumNeodymiumNeodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite...
- EuropiumEuropiumEuropium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
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.
Ore processing
The bastnäsiteBastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
ore was finely ground, and subjected to froth flotation
Froth flotation
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries...
to separate the bulk of the bastnäsite from the accompanying barite
Barite
Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...
, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, and dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
. 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
Cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...
concentrate, which was the insoluble residue left after the calcined bastnäsite had been leached with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
.
The lanthanides that dissolved as a result of the acid treatment were subjected to solvent extraction, to capture the europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
, and purify the other individual components of the ore. A further product included a lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
mix, depleted of much of the cerium, and essentially all of samarium
Samarium
Samarium is a chemical element with the symbol Sm, atomic number 62 and atomic weight 150.36. It is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3...
and heavier lanthanides. The calcination of bastnäsite had driven off the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
content, leaving an oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
-fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
, 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
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, which can cause reduction of quadrivalent cerium, led to an incomplete separation of cerium and the trivalent lanthanides.
History
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 world wide 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
Chevron Corporation
Chevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining,...
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
Molycorp
Molycorp Inc. is an American mining corporation headquartered in Greenwood Village, Colorado. The corporation, which is traded on the New York Stock Exchange, owns the Mountain Pass rare earth mine in California, a currently inactive mine which it proposes to reopen in 2011.The company’s...
, Inc. became a publicly-traded firm by selling 28,125,000 shares at $14 in its IPO
Initial public offering
An initial public offering or stock market launch, is the first sale of stock by a private company to the public. It can be used by either small or large companies to raise expansion capital and become publicly traded enterprises...
. The shares trade under the ticker symbol MCP on the NYSE.
Environmental impact
In 1998, chemical processing at the mine was stopped after a series of wastewater leaks. Hundreds of thousands of gallons of water carrying radioactive wasteRadioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
spilled into and around Ivanpah Dry Lake
Ivanpah Dry Lake
Ivanpah Lake is a dry lake bed in the Mojave Desert of San Bernardino County, California on the border of California and Nevada. Nestled in the Ivanpah Valley near Primm on Interstate 15, the lake is almost entirely within California. At the north edge of the lake lie the Nevada Welcome Center ...
.
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
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
and radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
, 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 activity
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 United States, 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 is owned by Molycorp Minerals LLC, which is a subsidiary of Molycorp Inc.. Molycorp plans to invest $500 million to reopen and expand the mine. The money was raised through an initial public offering of stock in Molycorp Inc. Current plans are for full mining operations to resume by the second half of 2011 as a result of increased demand for rare earth metals. In December 2010, Molycorp announced that it secured all the environmental permits needed to begin construction of a new ore processing plant at the mine; construction will begin in January 2011, and is expected to be completed by the end of 2012.