Gypsum
Gypsum is a very saft sulfate mineral componed o calcium sulfate dihydrate, wi the chemical formula CaSO4·2H2O.
It can be uised as a fertilizer, is the main constituent in mony furms o plaister an is widely mined. A very fine-grained white or lichtly tinted variety o gypsum, cried alabast, haes been uised for sculpture bi mony culturs includin Auncient Egyp, Mesopotamie an the Nottingham alabasts o medieval Ingland. It is the definition o a hairdness o 2 on the Mohs scale o mineral hardness. It furms as an evaporite mineral an as a hydration product o anhydrite.
| Gypsum | |
|---|---|
 Fibrous gypsum selenite shawin its translucent property. | |
| General | |
| Category | Sulfate minerals |
| Formula (repeatin unit) | CaSO4·2H2O |
| Strunz clessification | 07.CD.40 |
| Creestal seestem | Monoclinic 2/m – Prismatic |
| Space group | Monoclinic 2/m |
| Unit cell | a = 5.679(5) Å, b = 15.202(14) Å, c = 6.522(6) Å; β = 118.43°; Z=4 |
| Identification | |
| Colour | Colourless tae white; mey be yellae, tan, blue, pink, broun, reiddish brown or gray due tae impurities |
| Creestal habit | Massive, flat. Elangatit an generally prismatic crystals |
| Twinnin | Very common on {110} |
| Cleavage | Perfect on {010}, distinct on {100} |
| Fractur | Conchoidal on {100}, splintery parallel tae [001] |
| Tenacity | Flexible, inelastic. |
| Mohs scale haurdness | 1.5–2 (definin mineral for 2) |
| Skinkle | Vitreous tae silky, pearly, or waxy |
| Streak | White |
| Diaphaneity | Transparent tae translucent |
| Speceefic gravity | 2.31–2.33 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.519–1.521 nβ = 1.522–1.523 nγ = 1.529–1.530 |
| Birefringence | δ = 0.010 |
| Pleochroism | None |
| 2V angle | 58° |
| Fusibility | 5 |
| Solubility | Het, dilute HCl |
| References | |
| Major varieties | |
| Satin spar | Pearly, fibrous masses |
| Selenite | Transparent and bladed crystals |
| Alabast | Fine-grained, slightly colored |
References
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