Asbestos
| Asbestos | |
|---|---|
|
|
| General | |
| Category | Mineral |
| Strunz classification | 09.ED.15 |
| Dana classification | 71.01.02d.03 |
| Crystal system | Orthorhombic |
| Identification | |
| Formula mass | 277.11 g |
| Color | Green, red, yellow, white, blue |
| Crystal habit | Amorphous, granular, massive |
| Fracture | Fibrous |
| Mohs scale hardness | 2.5–3 |
| Luster | Silky |
| Streak | White |
| Optical properties | Biaxial |
| Birefringence | 0.008 |
| 2V angle | 20° to 60° |
| Dispersion | relatively weak |
| Ultraviolet fluorescence | Non-fluorescent |
Asbestos is a set of six naturally occurring silicate minerals, which all have in common their eponymous asbestiform habit: long (roughly 1:20 aspect ratio), thin fibrous crystals, with each visible fiber composed of millions of microscopic "fibrils" that can be released by abrasion and other processes. They are commonly known by their colors, as blue asbestos, brown asbestos, white asbestos, and green asbestos.
Asbestos mining existed more than 4,000 years ago, but large-scale mining began at the end of the 19th century, when manufacturers and builders began using asbestos for its desirable physical properties:sound absorption, average tensile strength, resistance to fire, heat, electricity, and affordability. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. These desirable properties made asbestos very widely used. Asbestos use continued to grow through most of the 20th century until public knowledge (acting through courts and legislatures) of the health hazards of asbestos dust outlawed asbestos in mainstream construction and fireproofing in most countries.
Prolonged inhalation of asbestos fibers can cause serious and fatal illnesses including lung cancer, mesothelioma, and asbestosis (a type of pneumoconiosis). Concern of asbestos-related illness in modern times began in the 20th century and escalated during the 1920s and 1930s. By the 1980s and 1990s, asbestos trade and use were heavily restricted, phased out, or banned outright in an increasing number of countries.
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