Magnesiocummingtonite

General Information:
 Chemical Formula:
(Mg,Fe++)7Si8O22(OH)2
 Composition:
(Molecular Weight = 836.02 gm)
Magnesium 15.26 % Mg
Iron 11.69 % Fe
Silicon 26.88 % Si
Hydrogen 0.24 % H 
Oxygen 45.93 % O 
 Empirical Formula:
Mg5.25Fe2+1.75Si8O22(OH)2
Physical Properties:
 Cleavage:
[110] Good
 Color:
brown, gray green, white, light gray, or dark green.
 Density:
3.13
 Hardness:
5-6 - Between Apatite and Orthoclase
 Luster:
Silky
 Streak:
white
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