Rare earth metals comprise the 17 naturally occurring rare earth elements (REEs) found in the Earth’s crust.

Commonly associated with the radioactive metal thorium (Th), the term “rare” earth elements is misleading since the more abundant light REEs are more prevalent in the earth’s crust than industrial metals such as chromium, nickel, zinc and lead.

They are essential for today’s global high-tech industry for products like smartphones, computers, medical CAT scans, wind turbines and hybrid cars.

Because of their lack of concentrated quantities, challenges in processing and a lengthy environmental permitting processes (seven to ten years) to open new mines, exploiting REE oxide ore deposits has been economically challenging in the United States.

Rare earth elements are found in:

• Lanthanum is a metal used in hybrid car batteries and lanterns.

• Misch metal, is a cerium alloy that generates a spark when struck. It’s used in the flints of cigarette lighters.

• Praseodynium adds to the emission of bright yellow light and is found in carbon arc lamps used in the motion picture industry.

• Neodymium-iron-boron magnets are used in stereo audio speakers.

• Lightweight promethium batteries are the preferred choice for satellites or space probes.

• Samarium, when combined with cobalt, is used as a magnet for specialized airplane motors.

• Europium is found in color cathode-ray tubes and liquid-crystal displays used in computers and televisions.

• Gadolinium is credited for control rods in nuclear power plants and in ear tumor detection.

• X-ray screens use phosphors that contain terbium to improve image quality.

• Dysprosium alloys are noted for their magnetic properties and used in CD Players.

• Holium lasers are used to treat glaucoma and reduce abnormal eye

• pressure.

• Eribium optical fibers are used in high-definition television (HDTV) signals carrying more information than their copper counterparts.

• Satellite imagery of the Earth’s surface uses lasers containing thulium.

• Ytterbium is used in making lasers.

• Lutetium is used as a catalyst in the petroleum industry to speed up or slow down chemical reactions.

• Bicycle frames and specialized lamps rely on scandium alloys.

• Often found in cutting tools and jet engines, are corrosion resistant yttrium alloys.

Both thorium and rare earth metals in Arizona are found in pegmatites, igneous rocks composed of rare elements and large crystals. Rare-earth bearing pegmatite localities in Arizona include the Rare Metals mine in the Aquarius Cliffs in Mohave County, producing rare-earth and thorium minerals such as allanite, chevkinite, euxenite, gadolinite and monzonite.

Found at the Kingman Feldspar mine in the Cerbat Mountains five miles north of Kingman, is allanite. Other deposits include the Bechetti Lease northeast of Prescott, the rare-earth-and thorium-bearing mineral davidite in the Quijotoa Mountains, the Uranium Basin claims in Mohave County wherein the thorium mineral uranothorite is found, and the Scott Lode near Quartzite with thorite deposits.

Holocene placers of rare-earth thorium minerals are found at the Cottonwood Ranch, 11 miles southwest of the San Xavier Mission, wherein dry steambeds yield slightly radioactive black sands composed of trace amounts of allanite several miles across.

By the mid-1960s, color television accelerated United States mining of rare earth minerals. Production decreased in the 1990s because of China’s entry into the rare earth mineral market. China currently supplies 97 percent of the 210,000 tons of world annual demand for rare earth minerals. Since 2010, the United States has renewed its interest in mining rare earth minerals after China cut back on exports.

While the Mountain Pass REE mine operated by Molycorp in the Mojave Desert California is the only domestic supplier of REE in the United States, recent discoveries of REE localities include tailings piles of mines in Arizona. Those in the Kingman area, Tombstone and Bisbee are currently initiating a heightened interest in future REE mining operations in Arizona.