General Information:
Chemical Formula:
CaSO4·2(H2O)
Composition:
(Molecular Weight = 172.17 gm)
Calcium 23.28 % Ca
Hydrogen 2.34 % H
Sulfur 18.62 % S
Oxygen 55.76 % O
Empirical Formula:
Ca(SO4)·2(H2O)
Environment:
Sedimentary evaporite deposits.
Locality:
Numerous localities worldwide. Naica, Chihuahua, Mexico.
Name Origin:
From the Greek, gyps meaning "burned" mineral. Selenite from the Greek in allusion to its pearly luster (moon light) on cleavage fragments.
Physical Properties:
Cleavage:
[???] Perfect, [???] Good
Color:
white, colorless, yellowish white, greenish white, or brown.
Density:
2.3
Diaphaniety:
Transparent to translucent
Habits:
Tabular - Form dimensions are thin in one direction., Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Massive - Fibrous - Distinctly fibrous fine-grained forms.
Hardness:
2 - Gypsum
Luminescence:
None.
Luster:
Pearly
Streak:
white
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