Mine Tales: Tungsten, Once Mined Here, Now an Import

Details: Category: Tungsten's News; Published on Friday, 29 August 2014 14:51

Tungsten’s hardness at elevated temperatures, tensile strength, corrosion resistance and good electrical and thermal conductivity make it a metal of choice used in industry. Tungsten has the highest melting point of all metals, at 6,170 degrees Fahrenheit (3,410 Celsius).

Tungsten minerals include wolframite, scheelite, powellite, cuprotungstite and tungstite. Wolframite and scheelite — the two main commercial ores — are often found in quartz veins and contact metamorphic scheelite deposits.

First discovered and isolated from its ore minerals in the 1780s, it was used chiefly in the manufacture of steel in the 19th century. By the 20th century, armor-piercing shells, electronics, high-speed tool steels and nuclear and aerospace applications increased demand for tungsten carbide.

Some states known for their tungsten deposits are California, Colorado, Montana, Utah and Arizona. Wolframite (Fe, Mn) WO4 was first identified in Arizona by territorial geologist W.P. Blake in 1896.

Arizona’s early tungsten mines included the Little Dragoon Mountains, started in 1900, and the Las Guijas district in Pima County, in 1901. Before World War I, the Blue Bird Mine in the Little Dragoon Mountains produced a record 2,200-pound nearly pure specimen of the wolframite tungsten mineral huebnerite.

Arizona’s most productive tungsten locality, the Boriana Mine in the Hualapai Mountains of Mohave County, 20 miles southeast of Kingman, yielded 149,000 units of tungsten trioxide (WO3) between 1915 and its closure in 1956.

Operated by the Yucca Tungsten Mining Co., which erected a 50-ton mill at the site, it was the largest producer of tungsten in Arizona during World War I. The Boriana Mining Co. acquired the mine in 1929. The Boriana Mine became the second-largest producer of tungsten in the United States in 1936-37, with a monthly output of 3,000 tons a month.

By the start of World War II, the mine consisted of 16,000 feet of workings with seven levels of drifts and received electric power from a transmission line from Boulder (later Hoover) Dam.

The Huachuca Mountains in Cochise County, notably the Hartford Mining District, was mined for tungsten found in skarns (metamorphic rock), veins or pegmatites (igneous rock).

Initially worked for gold and silver since the 1870s, 170 or more tons of tungsten concentrates varying between 60 percent to 78 percent WO3 had been produced by 1970 from mines including the Tungsten Reef Mine and James Group.

A small camp known as Reef was established in 1901 and lasted until 1926 with a post office, boarding house and population of 100.

In the early 1900s, W.F. Cody — better known as “Buffalo Bill” — worked 45 claims for gold and tungsten spread across 2,000 acres around Oracle known as the Campo Bonito District.

Scheelite, which turns bright blue under ultraviolet black light, was mined by the Cody-Dyer Arizona Mining & Milling Co. and shipped as an additive to a Pittsburgh steel company.

Thomas Edison used the high-grade tungsten ore mined by Cody’s operation, including the Maudina Tungsten and Pure Gold Tungsten Mines, in the manufacturing of tungsten filament light bulbs.

By 1965, total tungsten production in Arizona amounted to 280,000 short ton units WO3. Since the early 2000s, tungsten mines in China have supplied 85 percent of the world market, with Russia and Canada the next-greatest producers at a distant 4 percent and 3 percent, respectively.

The United States — the world’s largest tungsten consumer — stopped mining tungsten in 2000 with the closure of the Pine Creek Mine near Bishop, California, and now relies on imports or recycled scrap.

With a volatile geopolitical market coupled with new technologies in the 21st century, perhaps heightened domestic demand will renew exploration and exploitation of Arizona’s widely distributed tungsten deposits.

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