Armangite

General Information:
 Chemical Formula:
Mn26As+++18O50(OH)4(CO3)
 Composition:
(Molecular Weight = 3,704.99 gm)
Manganese 38.55 % Mn
Arsenic 36.40 % As
Hydrogen 0.11 % H 
Carbon 0.32 % C 
Oxygen 24.61 % O 
 Empirical Formula:
Mn2+26As18O50(OH)4(CO3)
Physical Properties:
 Cleavage:
[0001] Good
 Color:
black.
 Density:
4.43
 Diaphaniety:
Transparent to Opaque
 Hardness:
4 - Fluorite
 Streak:
brown
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