Homilite

 Homilite is a borosilicate mineral belonging to the gadolinite group of minerals with formula Ca2(Fe,Mg)B2Si2O10.

Homilite
General
CategoryNesosilicate
Formula
(repeating unit)		Ca2(Fe2+,Mg)B2Si2O10
Strunz classification8/B.29-30
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
Space groupP21/b
Unit cella = 9.78 Å,
b = 7.61 Å,
c = 4.78 Å; β = 90.56°; Z = ?
Identification
ColorGreenish to brownish black
Mohs scale hardness5–5+1⁄2
LusterVitreous, resinous
DiaphaneityOpaque
Specific gravity3.34
Optical propertiesBiaxial (+)
Refractive indexnα = 1.715 nβ = 1.725 nγ = 1.738
Birefringenceδ =
2V angleMeasured: 80°

It occurs as brown monoclinic crystals (space group P21/a[1]) within feldspar masses in pegmatite and was discovered in 1876 in Stoko island, Langesundfiord, Norway. The name is from the Greek for to occur together, in allusion to its association with meliphanite and allanite.

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
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Note

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License.