what is gypsum used for


Gypsum - Wikipedia, the free encyclopedia

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** Gypsum **

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This article is about the mineral. For other uses, see Gypsum
(disambiguation).

Gypsum
SeleniteGypsumUSGOV.jpgFibrous gypsum selenite showing its translucent
property
General
Category Sulfate minerals
Formula
(repeating unit) CaSO[4]·2H[2]O
Strunz classification 07.CD.40
Crystal symmetry 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
Color Colorless to white; may be yellow, tan, blue, pink, brown, reddish
brown or gray due to impurities
Crystal habit Massive, flat. Elongated and generally prismatic crystals
Crystal system Monoclinic 2/m – Prismatic
Twinning Very common on {110}
Cleavage Perfect on {010}, distinct on {100}
Fracture Conchoidal on {100}, splintery parallel to [001]
Tenacity Flexible, inelastic.
Mohs scale hardness 1.5–2 (defining mineral for 2)
Luster Vitreous to silky, pearly, or waxy
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.31–2.33
Optical properties Biaxial (+)
Refractive index n[α] = 1.519–1.521
n[β] = 1.522–1.523
n[γ] = 1.529–1.530
Birefringence δ = 0.010
Pleochroism None
2V angle 58°
Fusibility 5
Solubility Hot, dilute HCl
References ^[1]^[2]^[3]
Major varieties
Satin spar Pearly, fibrous masses
Selenite Transparent and bladed crystals
Alabaster Fine-grained, slightly colored

Gypsum crystals in the Cave of the Crystals in Mexico. Note person for
scale.

*Gypsum* is a soft sulfate mineral composed of calcium sulfate dihydrate,
with the chemical formula CaSO[4]·2H[2]O.^[3] It can be used as a
fertilizer, is the main constituent in many forms of plaster and in
blackboard chalk, and is widely mined. A massive fine-grained white or
lightly tinted variety of gypsum, called alabaster, has been used for
sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient
Rome, Byzantine


Source: en.wikipedia.org/wiki/Gypsum

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