Formula: Mn7(AsO4)2(OH)8
Origin of name: From Greek for to change (strong pleochroism)
Crystal system: Monoclinic
Crystal class: 2/m
Unit cell: a = 11.03 Å, b = 12.12 Å, c = 5.51 Å, b = 114.1°
Colour: Light to dark brownish red or purplish-red
Diaphaneity: Translucent
Luster: Vitreous, slightly greasy to oily on fresh fracture
Habit: Crystals slender prismatic or tabular; rosette-like aggregates
Hardness: 4.5
Specific gravity: 3.83
Cleavage: 1; {001} distinct
Streak: Grey to faint brown
Synonyms/varieties: Chloroarsenian
Comments: Formed as a rare secondary mineral in veinlets through metamorphosed manganese deposits; in a metamorphosed stratiform zinc ore body.
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