ASBESTOS (Gk. inextinguishable, incombustible, from 4, a negat. sbcnnynai, to extinguish). A fibrous mineral, used chiefly for protection against heat, its structure permitting it to be matted or woven. The asbestos of commerce belongs to two mineral species—viz., true asbestos and chrysolite. The former is a variety of amphibole (q.v.), closely allied to tremolite, actinolite, and hornblende. It is a silicate of magnesia and lime together, and iron-oxide and its fibres are sometimes corn bined together in a compact mass, sometimes easily separable, elastic, and flexible. It is gen erally of a whitish or greenish color. The variety known as Rock-co•k, resembling vegetable cork, is soft, easil? cut, and lighter than water. Rock-leather and Rock-wood are varieties of true asbestos, somewhat similar to Rock-cork, hut not so light. Chrysolite, the second mineral called asbestos, is a fibrous variety of ser pentine, a silicate of magnesia. The Italian product is true asbestos, Canadian asbestos being chrysolite. The finest variety of asbes tos, with easily separable fibres, is called anti anthus (Gk. unpollutable). Amianthus cloth was indestructible by fire, and was used by the ancients to enwrap (lead bodies placed on the funeral pile, in order to preserve the ashes of the body. Asbestos deposits of commereial value occur in Italy, Tasmania, New South Wales, Canada, and the United States. Asbestos is
now employed for boiler coverings, for the radi ating surfaces of heating apparatus, as an ab sorhent in lamps, as an insulator in electric mechanisms, and for a great many other pur poses in connection with manufactures, such as making paint, which forms an almost fireproof coat that protects wood against sparks and small flames. Cloths made of asbestos are used for curtains in theatres, for firemen's clothing, etc. Made into a lining felt, asbestos serves as a good insulator for heat, and has great value for packing steam duets, pistons, hot-air joints, etc. Abestos paper and board is made in much the same manner as ordinary paper and pasteboard, by reduetion of the mineral to pulp, and sub sequent pressing, drying, etc. The asbestos pro duced in Canada is almost pure white, and has long fibres. It can be spun into fine thread and woven into rope or yarn. Although the prop erties of asbestos were known to the ancients, and even to some extent utilized by them, the substance has been extensively employed for practical purposes only in recent times. Most of the American supply of asbestos is obtained from Canada. See the articles AMPHIBOLE; SER PENTINE; and ASBESTIC: and consult. .Tones.
rtsbesto.s, Its Properties and Uses (London, 1890) ; article on "Asbestos" ill Mineral Industry, Vol. VI. (New York, 1897).