| Tremolite | |
|---|---|
 | |
| General | |
| Category | Inosilicates |
| Formula | Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2 |
| IMA symbol | Tr[1] |
| Strunz classification | 9.DE.10 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (sameH-M symbol) |
| Space group | C2/m (no. 12) |
| Unit cell | a = 9.84 Å, b = 18.02 Å c = 5.27 Å; β = 104.95°; Z = 2 |
| Identification | |
| Color | White, gray, lavender to pink, light green, light yellow |
| Crystal habit | Elongated prismatic, or flattened crystals; also as fibrous, granular or columnar aggregates |
| Twinning | Simple or multiple, common parallel to {100}; rarely parallel to {001} |
| Cleavage | Perfect on {110} at 56° and 124°; partings on {010} and {100} |
| Tenacity | Brittle |
| Mohs scale hardness | 5–6 |
| Luster | Vitreous and silky |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.99–3.03 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.599 – 1.612 nβ = 1.613 – 1.626 nγ = 1.625 – 1.637 |
| Birefringence | δ = 0.026 |
| 2V angle | Measured: 86° to 88° |
| Ultravioletfluorescence | Short UV=yellow, Long UV=pink |
| References | [2][3][4][5][6] |
Tremolite is a member of theamphibole group ofsilicate minerals with composition Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms bymetamorphism of sediments rich indolomite andquartz, and occurs in two distinct forms, crystals and fibers. Tremolite forms a series withactinolite andferro-actinolite. Puremagnesium tremolite is creamy-white, but the color grades to dark green with increasingiron content. It has a hardness onMohs scale of 5 to 6.Nephrite, one of the two minerals known as the gemstonejade, is a green crystalline variety of tremolite.
The fibrous form of tremolite is one of the six recognised types ofasbestos. Inhalingasbestiform tremolite can lead toasbestosis,lung cancer and bothpleural andmalignant mesothelioma. Fibrous tremolite is sometimes found as a contaminant invermiculite,chrysotile (itself a type of asbestos), andtalc.
Tremolite is an indicator of metamorphic grade since at high temperatures it converts todiopside.
Tremolite occurs as a result ofcontact metamorphism of calcium- and magnesium-rich siliceoussedimentary rocks and ingreenschist facies metamorphic rocks derived fromultramafic or magnesiumcarbonate bearing rocks. Associated minerals includecalcite,dolomite,grossular,wollastonite,talc, diopside,forsterite,cummingtonite,riebeckite, andwinchite.[3]
Tremolite was first described in 1789 for an occurrence inCampolungo, Piumogna Valley,Leventina,Ticino (Tessin),Switzerland.[2]
One of the six recognized types ofasbestos, approximately 40,200 tons of tremolite asbestos is mined annually in India.[7] It is otherwise found as a contaminant.
