Wyoming's Rare Earth Elements

What are Rare Earth Elements?

REEs are a group of 17 metallic elements with similar physical and chemical properties that occur together in the periodic table. Sixteen of these occur in nature and are typically found in varying proportions in the same ore deposits. REEs are vital to industrialized societies worldwide as they are used in a range of products, including nuclear reactor components, cell phones, magnets, camera lenses, and batteries.

During the last 18 years, REE production and processing have centered in China, which by 2010 provided 95 to 97 percent of the world’s supply. When China reduced REE exports by 40 percent in 2010, as compared to 2009, world demand exceeded the supply. This inspired heightened REE exploration and development by other countries to meet demand and offset the elevated price. Molycorp’s Mountain Pass Mine in California reopened in 2010 and increased the United States’ supply for a short time. However, its 2015 closure and China’s stronghold on global supply has continued driving interest in securing REE resources to maintain U.S. national security.

World Deposits and Reserves

The largest known REE deposits occur in China, Australia, and North America, with much smaller reserves found in India, Brazil, Malaysia, and South Africa. Production has been dominated by China, with additional production from Australia, India, Malaysia, Russia, and Thailand. China's reserves are the largest. Estimates project that China has the largest percentage worldwide of REE reserves at about 36 percent, compared to the United States at about 13 percent. The Commonwealth of Independent States (Azerbaijan, Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, Uzbekistan, and Ukraine) controls about 19 percent, followed by Australia with more than 5 percent and India with 3 percent.

Current U.S. Production

In 2017, China supplied more than 80 percent of world REE production, with none produced in the United States. According to the U.S. Geological Survey, deposits of REE-bearing ore exist in California (MP Materials Mountain Pass mine), Nebraska, Colorado, New Mexico, Texas, New York, Alaska, and Wyoming.

Mining was in the planning stages for one major Wyoming REE deposit in the Bear Lodge Mountains in Crook County. Unfortunately, weak market conditions and a lengthy permitting process caused Rare Element Resources, Ltd. to temporarily suspend the project as of January 2016. The potential exists for the occurrence of additional REE deposits across the state.

Awareness of the diversity of REE deposit types is beneficial to exploration efforts. Economically, exploitable concentrations of REE are primarily derived from crystalline rocks. REEs are more common in alkaline igneous rocks and carbonatites than in mafic rocks. Rare earths typically occur as trivalent cations in rock-forming minerals in carbonates, oxides, phosphates, and silicates. REEs are chemically similar to thorium and are often found in minerals and rocks in association with this element. Economic concentrations of REE-host minerals are known from alkaline igneous rocks, carbonatites, and from a wide variety of dikes and veins that cross-cut alkaline intrusions and surrounding rocks.

REEs occur in a variety of rock units across Wyoming. Reported Precambrian REE occurrences are hosted by pegmatites, veins and dikes, faults and shear zones, metacarbonate rocks, disseminated minerals in generally alkalic igneous rocks, and metasediments. Sedimentary occurrences in paleoplacers are found primarily in the Cambrian Flathead Sandstone and the Cretaceous Mesaverde Formation as well as local, smaller deposits in numerous units. Disseminations of REEs are also reported within phosphate-rich rock of the Permian Phosphoria Formation. Tertiary-aged hosts include alkaline igneous rocks, carbonatite veins, dikes, hydrothermal zones, paleoplacers, and apparent depositions from solution movement within sandstones. Quaternary REE hosts can be found in alluvial placers and paleoplacers (King and Harris, 2002; Sutherland and others, 2013).

Numerous minerals are known to contain REEs as essential constituents, and a greater number contain REEs as accessory elements. Only a few of these minerals host large enough concentrations of REEs to be considered ore minerals. Allanite and monazite occur as relatively common accessory minerals within many types of felsic igneous rocks. Other REE-bearing minerals can be uncommon and are often hosted in generally uncommon rock types. Worldwide, the principal commercial sources of REE are the minerals bastnasite, loparite, monazite, and xenotime, and rare earth ion-adsorption clays. When discussing principal REE-bearing minerals specific to the United States, Long and others (2010) omit loparite and ion-adsorption clays but add euxenite and allanite, although other REE-bearing minerals are also present.

Of the principal REE-bearing minerals, allanite, bastnasite, euxenite, monazite, and xenotime are known to occur in Wyoming. Although not primary REE sources, ewaldite and mckelveyite were actually discovered with association to trona beds in the Green River Formation in Sweetwater County. The table below lists minerals reported in Wyoming that contain REEs. Mineral formulas are variable depending on the source cited and on subvarieties that may contain differing elemental substitutions.

REE-bearing minerals that occur in Wyoming.

Consumer products that rely on integral use of REEs include catalytic converters, cell phones, digital cameras, and computers. Additionally, neodymium, samarium, gadolinium, dysprosium, and praseodymium are used in high-power permanent magnets where weight and space are of concern. The table below shows typical uses of REEs. These applications range from computer hard drive motors and MRI scanners to wind generators. A typical hybrid car, such as a Toyota Prius, contains around 11.3 kg (25 lbs) of REEs, mostly lanthanum, in its rechargeable battery and about 2 kg (4.5 lbs) of neodymium and dysprosium in its drive motor. Smart phones and LED lights each contain less than a gram of REEs (Molycorp, 2015a).

REEs are also used for national security purposes. The U.S. Department of Defense uses REEs in lasers, precision-guided munitions, communications and radar systems, avionics, night-vision equipment, satellites, range finders, and control systems. These security-related uses make China’s control of REEs a subject of concern to many nations.

Typical uses of the rare earth elements.