Ferroglaucophane

General Information:
 Chemical Formula:
[ ]Na2(Fe++3Al2)Si8O22(OH)2
 Composition:
(Molecular Weight = 878.17 gm)
Sodium 5.24 % Na
Aluminum 6.14 % Al
Iron 19.08 % Fe
Silicon 25.59 % Si
Hydrogen 0.23 % H 
Oxygen 43.73 % O 
 Empirical Formula:
Na2Fe2+3Al2(Si8O22)(OH)2
 IMA Status:
Approved IMA 1978
Physical Properties:
 Cleavage:
[110] Perfect
 Color:
blue, blue black, gray, or gray blue.
 Density:
3.04 - 3.23, Average = 3.13
 Diaphaniety:
Transparent to Translucent
 Hardness:
6 - Orthoclase
 Luster:
Vitreous - Dull
 Streak:
blue gray
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