Arsenolite

Arsenic trioxide is the most important commercial compound of arsenic, and the main starting material for arsenic chemistry. It is the highly toxic byproduct of certain kinds of ore processing, for example gold mining.
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General Information:
 Chemical Formula:
As2O3
 Composition:
(Molecular Weight = 197.84 gm)
Arsenic 75.74 % As
Oxygen 24.26 % O 
 Empirical Formula:
As2O3
 Environment:
Secondary mineral from As bearing rocks.
 Locality:
Amargosa mine, San Bernadino Co., California, USAl
Physical Properties:
 Cleavage:
[111] Perfect, [111] Perfect, [111] Perfect
 Color:
blue, white, light yellow, or red.
 Density:
3.7
 Diaphaniety:
Transparent to translucent
 Habits:
Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite)., Encrustations - Forms crust-like aggregates on matrix.,
 Hardness:
1.5 - Between Talc and Gypsum
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous - Dull
 Streak:
white
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ARSENOLITE