Arsenolite

Formula:  As₂O₃

Origin of name:  From composition, arsenic

Crystal system:  Cubic

Crystal class:  4/m -3 2/m

Twinning:

Unit cell:   a = 11.08 Å

Colour:  White, yellowish, bluish or reddish if impure

Diaphaneity: Transparent

Luster:  Vitreous to silky

Habit:  Crystals octahedral or capillary; crusts; stalactitic, botryoidal, earthy

Hardness:  1.5

Specific gravity:  3.86 to 3.88

Cleavage:  1; {111} distinct

Tenacity:  

Streak: White to pale yellowish white

Synonyms/varieties:

Comments:  Dimorphous with claudetite. Taste astringent, sweetish, a very toxic substance. Occurs as an oxidation product of other arsenic-bearing sulphides in hydrothermal veins, may be formed in mine fires or in burning coal seams.