Aerugite

Aerugite is a rare complex nickel arsenate mineral with a variably reported formula: Ni9(AsO4)2AsO6. It forms green to deep blue-green trigonal crystals. It has a Mohs hardness of 4 and a specific gravity of 5.85 to 5.95.It was first described in 1858 in either the South Terres mine of Cornwall, England or in Erzgebirge, Saxony, Germany. The origin is disputed. The most common occurrence is as an incrustation on furnace walls in which ores are roasted. Its name comes from the Greek word aerugo for copper rust.
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General Information:
 Chemical Formula:
([ ],Ni)9(AsO4)2(AsO6) (?)
 Composition:
(Molecular Weight = 976.97 gm)
Nickel 54.07 % Ni
Arsenic 23.01 % As
Oxygen 22.93 % O 
 Empirical Formula:
Ni9As3O14
 Environment:
Found in the walls of furnaces used to roast ore.
 IMA Status:
Approved IMA 1965
 Locality:
TL: South Terres mine, St Austell, Cornwall, England.
 Name Origin:
Named from the Greek for 'copper rust', in allusion to its appearance.
Physical Properties:
 Color:
deep blue green or green.
 Density:
5.85 - 5.95, Average = 5.9
 Diaphaniety:
Opaque
 Habits:
Massive - Uniformly indistinguishable crystals forming large masses., Euhedral Crystals - Occurs as well-formed crystals showing good external form., Encrustations - Forms crust-like aggregates on matrix.
 Hardness:
4 - Fluorite
 Streak:
greenish white
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