Asbestos is a generic term for six naturally-occurring fibrous minerals: chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite. Chrysotile, a fibrous form of serpentine, is the most common type of asbestos, followed by amosite and crocidolite. Asbestos has been mined in China, Italy, Russia, South Africa, the United States, and Zimbabwe. The largest known deposit of asbestos is found in Quebec; Canada produces 40 percent of the world's supply of fibrous minerals.

Asbestos has many useful properties. It is highly resistant to chemical corrosives and heat, has high tensile strength, and is a good nonconductor of electricity. Its hollow fibers make asbestos an excellent insulator. It is flexible and inflammable. Some types of asbestos occur in long fibers which may be spun into pure mineral yarns; shorter-fibered grades of asbestos may be blended with such materials as cotton or glass wool, and "nonspinning" asbestos, grades with fibers too short to...