Andradite

Andradite is a species of the Garnet Group. It is a nesosilicate, with formula Ca3Fe2Si3O12. Andradite includes 3 varieties:Melanite: Black in color, usually not cut as a gemstone.Demantoid: Vivid green in color, one of the most valuable and rare stones in the gemological world.Topazolite: Yellow-green in color and sometimes of high enough quality to be cut into a faceted gemstone.Andradite also is found in rarely colorless.
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Noun
1. a garnet consisting of calcium iron silicate and having any color ranging from yellow and green to brown and black; used as gemstone
(hypernym) garnet
(hyponym) demantoid

n. andradite, a garnet consisting of calcium iron silicate

General Information:
 Chemical Formula:
Ca3Fe+++2(SiO4)3
 Composition:
(Molecular Weight = 508.18 gm)
Calcium 23.66 % Ca
Iron 21.98 % Fe
Silicon 16.58 % Si
Oxygen 37.78 % O 
 Empirical Formula:
Ca3Fe2+2(SiO4)3
 Environment:
Igneous and metamorphic rocks.
 Locality:
Magnet Cove, Arkansas.
 Name Origin:
Andradite is named after the Brazilian mineralogist J. B. de Andrada e Silva (1763-1838). Demantoid is named after its adamantine luster.
Physical Properties:
 Cleavage:
None
 Color:
black, yellowish brown, red, greenish yellow, or gray.
 Density:
3.7 - 4.1, Average = 3.9
 Diaphaniety:
Transparent to translucent
 Habits:
Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Euhedral Crystals - Occurs as well-formed crystals showing good external form., Massive - Uniformly indistinguisha ble crystals forming large masses.
 Hardness:
6.5-7 - Pyrite-Quartz
 Luminescence:
None.
 Luster:
Vitreous (Glassy)
 Streak:
white
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ANDRADITE