Chrysotile
Chrysotile or white asbestos is the most commonly encountered form of asbestos, accounting for approximately 95% of the asbestos in the United States and a similar proportion in other countries. It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group. Its idealized chemical formula is Mg3(Si2O5)(OH)4. The material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled.
| Chrysotile | |
|---|---|
| General | |
| Category | Phyllosilicates Kaolinite-serpentine group |
| Formula (repeating unit) | Mg3(Si2O5)(OH)4 (ideal) |
| IMA symbol | Ctl |
| Strunz classification | 9.ED.15 |
| Crystal system | Monoclinic: clinochrysotile (most common) Orthorhombic: orthochrysotile and parachrysotile (both rare) |
| Crystal class | Clinochrysotile: prismatic (2/m) Orthochrysotile and parachrysotile: pyramidal (mm2) |
| Space group | Clinochrysotile: C2/m Orthochrysotile and parachrysotile: Ccm21 |
| Identification | |
| Formula mass | 277.11 g/mol (ideal) |
| Colour | White to greyish green |
| Crystal habit | Acicular |
| Fracture | Fibrous |
| Mohs scale hardness | 2.5–3 |
| Lustre | Silky |
| Streak | White |
| Diaphaneity | Translucent |
| Density | 2.53 g/ml |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.569, nγ = 1.570 |
| Birefringence | 0.001 (max) |
| Dispersion | Relatively weak |
| Extinction | parallel |
| Melting point | 600–850 °C (1,112–1,562 °F) (decomposes) |
| Fusibility | dehydrates at 550–750 °C (1,022–1,382 °F) |
| Diagnostic features | White to grayish green thin, flexible curved fiber |
| Solubility | Insoluble in water Fibres degrade in dilute acid |
| References | |
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