High tensile strength along with chemical, electric, fire and heat resistance have made asbestos a valuable industrial material worldwide.

More than 95 percent of the asbestos used in the United States is the chrysotile type in the serpentine family, which is the least harmful of the six different silicate minerals which comprise asbestos.

Those in the amphibole family include amosite, crocidolite, anthophyllite, tremolite and actinolite.

The word chrysotile is derived from the Greek “krysos” meaning gold and “tilos” meaning fiber.

Chrysotile deposits in Arizona were formed by contact metamorphism, a reaction of rock minerals to magma.

Minor asbestos deposits were discovered at the Grand Canyon in 1872, however; Arizona’s greatest asbestos deposits of commercial value are located in Gila County in the Salt River District, named for the salt springs that occur along the river.

Found in Mescal limestone intruded by diabase, Arizona’s asbestos deposits have the unique quality of naturally iron-free chrysotile spinning fiber used by the U.S. navy in electric-cable coverings on warships.

Its high strength and non-conductive qualities make it the preferred material for fire-proofing and insulation. It’s used in woven brake linings, safety clothing, textiles, roofing tiles and home siding.

The first commercial production of asbestos in Arizona occurred in 1903 when the Hance Asbestos Mining Co. secured several tons at the bottom of the Grand Canyon, opposite Grand View.

Several years later, William Wallace Bass — who filed over a dozen copper and asbestos claims along the rim of the Grand Canyon in the late 19th century — sold six tons of asbestos to China, France and the United States valued at $1,500 per ton.

Bass designed trails and built a cable tram across the Colorado River at Hakatai Canyon to transport ore. Other minor localities in Arizona for asbestos include the Abril Mine and Empire No. 2 Shaft in Cochise County, Cemetery Ridge in Yuma County, Putnam Wash in Pinal County and the Dome Rock Mountains in La Paz County.

Since 1913 over 160 asbestos mines operated in Central Arizona, notably around the Salt River Canyon region. Covering over 2,000 square miles of rugged terrain and steep canyons, the region produced a minimum of 75,000 tons of asbestos before the closure of the mines in the early 1980s.

Burro pack trains transported asbestos from Ash Creek to the rail at Globe. The small town of Chrysotile, 37 miles northeast of Globe, was established in 1916 and operated for several decades under the Johns-Manville Co., which employed over 150 miners in the area.

Chrysotile included a post office, tents, stone houses, a blacksmith shop and power plant. It contributed asbestos for insulation in the hydroelectric plant of the Hoover Dam in the 1930s.

By the 1970s, scientific studies began to link respiratory issues including lung and mesothelioma cancer to high levels of exposure of microscopic fibers of asbestos measuring less than 5 microns in diameter.

Asbestos usage in the United States peaked in 1973 with 800,000 tons compared to 1,000 tons in 2012 after the U.S. government implanted laws strictly regulating its usage. The last asbestos mines closed in Arizona during the early 1980s.

The last asbestos mine to operate in the United States was the KCAC mine in San Benito County, California, which closed in 2002.

Asbestos mining continues in other countries, including the world’s current greatest producer, Russia, which mined over 1 million tons in 2012. The small city of Asbest, Russia, hosts the world’s largest open pit asbestos mine, Uralasbest, (seven miles long and one and a half miles wide) exporting its product to China and India.

The Phillips Asbestos Mine in the Salt River District remains a popular locality for mineral collectors to find specimens of chrysotile, aragonite and serpentine.

William Ascarza is an archivist, historian and author. Email him at mining@tucson.com

Sources: Raymond Harris (2004), “Asbestos in Arizona,” Arizona Geology, Arizona Geological Survey Vol. 34, No. 1; Gene Knuckey (2007), “Chrysotile, Arizona,” 1914 to 1945; L.A. Stewart (1955), “Chrysotile-Asbestos Deposits in Arizona,” Bureau of Mines Information Circular 7706; B.S. Van Gosen and J.P. Clinkenbeard (2011), “Reported Historic Asbestos Mines, Historic Asbestos Prospects and Other Natural Occurrences of Asbestos in California: U.S. Geological Survey Open-File Report 2011-1188.”