What is Asbestos?
Asbestos is composed of minerals, known since antiquity, with long, thin fibrous crystals. The word "asbestos" is derived from a Greek adjective meaning inextinguishable. The Greeks termed asbestos the "miracle mineral" because of its soft and pliant properties, as well as its ability to withstand heat.
Asbestos became increasingly popular among manufacturers and builders in the late 19th century due to its resistance to heat, electricity and chemical damage, sound absorption and tensile strength. When asbestos is used for its resistance to fire or heat, the fibres are often mixed with cement or woven into fabric or mats. Asbestos is used in brake shoes and gaskets for its heat resistance, and in the past was used on electric oven and hotplate wiring for its electrical insulation at elevated temperature, and in buildings for its flame-retardant and insulating properties, tensile strength, flexibility, and resistance to chemicals.
The inhalation of asbestos fibres can cause serious illnesses, including mesothelioma and asbestosis. Since the mid 1980s, many uses of asbestos are banned in many countries.
Types of asbestos and associated fibres
Six minerals are defined as "asbestos" including: chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite.
Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks which is common throughout the world. The rocks are called serpentine because their fibres curl; chrysotile fibres are curly as opposed to fibres from amosite, crocidolite, tremolite, actinolite, and anthophyllite which are needlelike. Chrysotile, along with other types of asbestos, has been banned in dozens of countries and is only allowed in the United States and Europe in very limited circumstances. Chrysotile is used more than any other type and accounts for about 95% of the asbestos found in buildings in America. Applications where chrysotile might be used include the use of joint compound. It is more flexible than amphibole types of asbestos; it can be spun and woven into fabric.
Amosite, CAS No. 12172-73-5, is a trade name for the amphiboles belonging to the Cummingtonite - Grunerite solid solution series, commonly from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for amosite is Fe7Si8O22(OH)2. It is found most frequently as a fire retardant in thermal insulation products and ceiling tiles.