Magnesio-arfvedsonite

General Information:
 Chemical Formula:
NaNa2(Mg4Fe++)Si8O22(OH)2
 Composition:
(Molecular Weight = 832.72 gm)
Sodium 8.28 % Na
Magnesium 11.67 % Mg
Iron 6.71 % Fe
Silicon 26.98 % Si
Hydrogen 0.24 % H 
Oxygen 46.11 % O 
 Empirical Formula:
Na3Mg4Fe3+(Si8O22)(OH)2
 IMA Status:
Approved IMA 1978
Physical Properties:
 Color:
black or gray.
 Density:
3.17
 Diaphaniety:
Subopaque
 Hardness:
5-6 - Between Apatite and Orthoclase
 Luster:
Vitreous (Glassy)
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