![Mountainpass 2011](https://upload.wikimedia.org/wikipedia/commons/d/df/Mountainpass_2011.jpg)
The Mountain Pass Mine, owned by
MP Materials
MP Materials Corp. is an American rare-earth materials company headquartered in Las Vegas, Nevada. MP Materials owns and operates the Mountain Pass mine, the only operating rare earth mine and processing facility in the United States. MP Materia ...
, is an open-pit mine of
rare-earth element
The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...
s on the south flank of the
Clark Mountain Range in California, southwest of
Las Vegas, Nevada
Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Vegas ...
. In 2020 the mine supplied 15.8% of the world's rare-earth production. It is the only rare-earth mining and processing facility in the United States.
As of 2022, work is ongoing to restore processing capabilities for domestic light rare earth elements (LREEs) and work has been funded by the
United States Department of Defense
The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...
to restore processing capabilities for heavy rare earth metals (HREEs) to alleviate supply chain risk.
Geology
The Mountain Pass deposit is in a 1.4 billion-year-old
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...
intruded into
gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
. It contains 8% to 12% rare-earth oxides, mostly contained in the mineral
bastnäsite
The mineral bastnäsite (or bastnaesite) is one of a family of three carbonate-fluoride minerals, which includes bastnäsite-( Ce) with a formula of (Ce, La)CO3F, bastnäsite-( La) with a formula of (La, Ce)CO3F, and bastnäsite-( Y) with a formul ...
.
Gangue
In mining, gangue () is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit. It is thus distinct from overburden, which is the waste rock or materials overlying an ore or mineral body t ...
minerals include
calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
,
barite
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
, and
dolomite Dolomite may refer to:
*Dolomite (mineral), a carbonate mineral
*Dolomite (rock), also known as dolostone, a sedimentary carbonate rock
*Dolomite, Alabama, United States, an unincorporated community
*Dolomite, California, United States, an unincor ...
. It is regarded as a world-class rare-earth mineral deposit. The metals that can be extracted from it include:
cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...
,
lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...
,
neodymium
Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes i ...
, and
europium
Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
.
At 1 July 2020,
Proven and Probable Reserves, using a 3.83% total rare-earth oxide (REO) cutoff grade, were 18.9 million tonnes of ore containing 1.36 million tonnes of REO at an average grade of 7.06% REO.
Ore processing
To process
bastnäsite
The mineral bastnäsite (or bastnaesite) is one of a family of three carbonate-fluoride minerals, which includes bastnäsite-( Ce) with a formula of (Ce, La)CO3F, bastnäsite-( La) with a formula of (La, Ce)CO3F, and bastnäsite-( Y) with a formul ...
ore, it is finely ground and subjected to
froth flotation
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...
to separate the bulk of the bastnäsite from the accompanying
barite
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
,
calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
, and
dolomite Dolomite may refer to:
*Dolomite (mineral), a carbonate mineral
*Dolomite (rock), also known as dolostone, a sedimentary carbonate rock
*Dolomite, Alabama, United States, an unincorporated community
*Dolomite, California, United States, an unincor ...
. Marketable products include each of the major intermediates of the ore dressing process: flotation concentrate, acid-washed flotation concentrate,
calcined
Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), genera ...
acid-washed bastnäsite, and finally a
cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...
concentrate, which was the insoluble residue left after the calcined bastnäsite had been leached with
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
.
The lanthanides that dissolve as a result of the acid treatment are subjected to
solvent extraction
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
to capture the
europium
Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
and purify the other individual components of the ore. A further product includes a
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...
mix, depleted of much of the cerium, and essentially all of
samarium
Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...
and heavier lanthanides. The calcination of bastnäsite drives off the
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
content, leaving an
oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
-
fluoride
Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...
, in which the cerium content oxidizes to the less-basic quadrivalent state. However, the high temperature of the calcination gives less-reactive oxide, and the use of
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
, which can cause reduction of quadrivalent cerium, leads to an incomplete separation of cerium and the
trivalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
lanthanides.
History
![Rareearth production](https://upload.wikimedia.org/wikipedia/commons/9/93/Rareearth_production.svg)
The Mountain Pass deposit was discovered in 1949 by Herbert S. Woodward, Clarence Watkins and P. A. Simon, who noticed anomalously high radioactivity. Molybdenum Corporation of America bought most of the mining claims, and began small-scale production in 1952.
Production expanded greatly in the 1960s, to supply demand for
europium
Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
used in color television screens. Between 1965 and 1995, the mine supplied most of the worldwide rare-earth metals consumption.
Molybdenum Corporation of America changed its name to
Molycorp
Molycorp Inc. was an American mining corporation headquartered in Greenwood Village, Colorado. The corporation, which was formerly traded on the New York Stock Exchange, owned the Mountain Pass rare earth mine in California. It filed for bankrup ...
in 1974. The corporation was acquired by
Union Oil
Union Oil Company of California, and its holding company Unocal Corporation, together known as Unocal was a major petroleum explorer and marketer in the late 19th century, through the 20th century, and into the early 21st century. It was headqu ...
in 1977, which in turn became part of
Chevron Corporation
Chevron Corporation is an American multinational energy corporation. The second-largest direct descendant of Standard Oil, and originally known as the Standard Oil Company of California (shortened to Socal or CalSo), it is headquartered in S ...
in 2005.
[David Danelski]
Expansion in works for S.B. County mine with troubled environmental past
, The Biz Press, February 9, 2009.
In 1998, the mine's separation plant ceased production of refined rare earth compounds; it continued to produce bastnäsite concentrate.
The mine closed in 2002 after a toxic waste spill and wasn't reopened due to competition from Chinese suppliers, though processing of previously mined ore continued.
In 2008, Chevron sold the mine to privately held Molycorp Minerals LLC, a company formed to revive the Mountain Pass mine. Molycorp announced plans to spend $500 million to reopen and expand the mine, and on July 29, 2010, it raised about $400 million through an
initial public offering
An initial public offering (IPO) or stock launch is a public offering in which shares of a company are sold to institutional investors and usually also to retail (individual) investors. An IPO is typically underwritten by one or more investment ...
, selling 28,125,000 shares at $14 under the ticker symbol MCP on the New York Stock Exchange.
In December 2010, Molycorp announced that it had secured all the environmental permits needed to build 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. On August 27, 2012, the company announced that mining had restarted.
The processing plant was in full production on June 25, 2015, when Molycorp filed for Chapter 11 bankruptcy with outstanding bonds in the amount of $US 1.4 billion. The company's shares were removed from the NYSE.
In August 2015, it was reported that the mine was to be shut down.
On August 31, 2016, Molycorp Inc. emerged from bankruptcy as Neo Performance Materials, leaving behind the mine as Molycorp Minerals LLC in its own separate Chapter 11 bankruptcy. As of January 2016, its shares were traded OTC under the symbol MCPIQ.
Mountain Pass was acquired out of bankruptcy in July 2017 with the goal of reviving America's rare earth industry. MP Materials resumed mining and refining operations in January 2018.
Current ownership
MP Materials is 51.8%-owned by US hedge funds JHL Capital Group (and its CEO James Litinsky) and QVT Financial LP, while Shenghe Resources Holding Co. Ltd., a partially
state-owned enterprise
A state-owned enterprise (SOE) is a Government, government entity which is established or nationalised by the ''national government'' or ''provincial government'' by an executive order or an act of legislation in order to earn Profit (econom ...
of the
Government of China
The Government of the People's Republic of China () is an Authoritarianism, authoritarian political system in the China, People's Republic of China under the exclusive political leadership of the Chinese Communist Party (CCP). It consists of Leg ...
, holds an 8.0% stake. Apart from institutions, the public owns 18%.
Environmental impact
In the 1980s, the company began piping wastewater up to 14 miles to evaporation ponds on or near
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 no ...
, 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 is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
and
radium
Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather t ...
, 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 and chemical processing at the mine were 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
Union Oil Company of California, and its holding company Unocal Corporation, together known as Unocal was a major petroleum explorer and marketer in the late 19th century, through the 20th century, and into the early 21st century. It was headqu ...
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 passed a key county inspection in 2007.
Current activity
![Mountain Pass Rare Earth Mine & Processing Facility](https://upload.wikimedia.org/wikipedia/commons/4/4e/Mountain_Pass_Rare_Earth_Mine_%26_Processing_Facility.jpg)
Since 2007, China has restricted exports of REEs (rare earth elements) and imposed export tariffs, both to conserve resources and to give preference to Chinese manufacturers. In 2009, China supplied more than 96% of the world's REEs. 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 so reliant on a single supplier country.
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
The Committee on Science, Space, and Technology is a committee of the United States House of Representatives. It has jurisdiction over non-defense federal scientific research and development. More specifically, the committee has complete jurisdic ...
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.
After China doubled import duties on rare earth concentrates to 25% as a result of the
US-China trade war, MP Materials said, in May 2019, it will start its own partial processing operation in the United States by 2020, though full processing operations without Shenghe Resources have been delayed to 2022.
[ (published 05-26-2019)] According to Bloomberg, China in 2019 established a plan for restricting U.S. access to Chinese heavy rare earth elements, should the punitive step be deemed necessary.
In 2022, the company announced that it had secured
Department of Defense Department of Defence or Department of Defense may refer to:
Current departments of defence
* Department of Defence (Australia)
* Department of National Defence (Canada)
* Department of Defence (Ireland)
* Department of National Defense (Philippin ...
grants to support both light rare earth elements (LREEs) and heavy rare earth elements (HREEs).
References
Other sources
*
*
*
*
External links
* {{Official website, http://www.mpmaterials.com, MP Materials
Carbonatite occurrences
Geography of San Bernardino County, California
Surface mines in the United States
Buildings and structures in San Bernardino County, California
Mines in California
Rare_earth_mines