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Anhydrite is a mineral—anhydrous calcium sulphate, CaSO4.
| Anhydrite | |
|---|---|
Anhydrite, Chihuahua, Mexico | |
| General | |
| Category | Sulphate mineral |
| Formula (repeatin unit) | Anhydrous calcium sulphate:CaSO4 |
| Strunz clessification | 07.AD.30 |
| Dana clessification | 28.3.2.1 |
| Creestal seestem | Orthorhombic – dipyramidal |
| Space group | Orthorhombic 2/m 2/m 2/m |
| Unit cell | a = 6.245(1) Å, b = 6.995(2) Å, c = 6.993(2) Å; Z = 4 |
| Identification | |
| Colour | Colourless tae fauch blae or violet gif transparent; white, mauve, rose, fauch broun or gray frae includit impurities |
| Creestal habit | Rare tabular an prismatic crystals. Uisually occurs as fibrous, parallel veins that break aff intae cleavage fragments. Occurs as grainy, massive, or nodular masses an aw. |
| Twinnin | Simple or repeatitly on {011} common; contact twins rare on {120} |
| Cleavage | [010] perfect [100] perfect [001] guid, resultin in pseudocubic fragments |
| Fractur | Conchoidal |
| Tenacity | Brickle |
| Mohs scale haurdness | 3.5 |
| Skinkle | Pearly on {010} vitreous tae glittie on {001} vitreous on {100} |
| Streak | White |
| Diaphaneity | Skyre tae leamin |
| Speceefic gravity | 2.97 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.567–1.574 nβ = 1.574–1.579 nγ = 1.609–1.618 |
| Birefringence | δ = 0.042–0.044 |
| Pleochroism | For violet varieties X = colourless tae fauch yellae or rose Y = fauch violet or rose Z = violet. |
| 2V angle | 56–84° |
| Fusibility | 2 |
| Ither chairacteristics | Some specimens fluoresce; mony mair fluoresce efter heatin |
| References | [1][2][3][4] |
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