Geigerite

Geigerite is a mineral, a complex hydrous manganese arsenate with formula: Mn5(AsO3OH)2(AsO4)2·10H2O. It forms triclinic pinacoidal vitreous colorless, red to brown crystals. It has a Mohs hardness of 3 and a specific gravity of 3.05.It was discovered in Grischun, Switzerland in 1989. It was named in honor of Dr. Thomas Geiger (1886–1976), Wiesendangen, Switzerland, who studied the Falotta manganese ores.
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General Information:
 Chemical Formula:
Mn5(AsO3OH)2(AsO4)2·10(H2O)
 Composition:
(Molecular Weight = 1,012.54 gm)
Manganese 27.13 % Mn
Arsenic 29.60 % As
Hydrogen 2.19 % H 
Oxygen 41.08 % O 
 Empirical Formula:
Mn2+5(AsO3OH)2(AsO4)2·10(H2O)
 IMA Status:
Approved IMA
Physical Properties:
 Cleavage:
[???] Perfect
 Color:
red or colorless.
 Density:
3.05
 Diaphaniety:
Transparent to Translucent
 Hardness:
3 - Calcite
 Luster:
Vitreous - Pearly
 Streak:
white
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