The Mountain Pass Rare Earth Mine is an open-pit
mine of rare-earth elements on the south flank
of the Clark Mountain Range, just north of
the unincorporated community of Mountain Pass,
California, United States.
The mine once supplied most of the world's
rare-earth elements.
Owned by MP Materials, it is the only rare
earth mining and processing facility in the
United States.
== Geology ==
The Mountain Pass deposit is in a 1.4 billion-year-old
Precambrian carbonatite intruded into gneiss.
It 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, and europium.
In 2008, remaining reserves using a 5% cutoff
grade were estimated to exceed 20 million
tons of ore that averages 8.9% rare-earth
oxides.
== Ore processing ==
To process bastnäsite ore, it is 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 dissolve as a result
of the acid treatment are subjected to solvent
extraction to capture the europium and purify
the other individual components of the ore.
A further product includes a lanthanide mix,
depleted of much of the cerium, and essentially
all of samarium and heavier lanthanides.
The calcination of bastnäsite drives off
the carbon dioxide content, leaving an oxide-fluoride,
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, which can cause reduction
of quadrivalent cerium, leads to an incomplete
separation of cerium and the trivalent lanthanides.
== History ==
The Mountain Pass deposit was discovered in
1949 by a uranium prospector who noticed anomalously
high radioactivity.
The Molybdenum Corporation of America bought
the mining claims, and began small-scale production
in 1952.
Production expanded greatly in the 1960s,
to supply demand for europium used in color
television screens.
Between 1965 and 1995, 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.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, though processing
of previously mined ore continued, in response
to both environmental restrictions and competition
from Chinese suppliers.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, 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.
Affiliates of two U.S. investment fund advisors,
JHL Capital Group LLC and QVT Financial LP
and Shenghe Resources Holding Co., a Chinese
minority shareholder, acquired Mountain Pass
in July 2017 with the goal of reviving America’s
rare earth industry.
The venture does business under the name MP
Materials (www.mpmaterials.com).
MP Materials resumed mining and refining operations
in January 2018.
=== Environmental impact ===
In the 1980s, the company began piping wastewater
up to 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 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 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 ===
Since 2007, China has restricted exports of
REEs 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
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.As
a result of the US-China trade war, MP Materials
has said it will start its own processing
operation in the United States by 2020, after
China doubled import duties on concentrates
to 25%.
According to Bloomberg, "China Has a Rare
Earths Plan Ready to Go if Trade War Deepens
