Formula: MnO2
Origin of name: from Greek for fire and to wash
Crystal system: tetragonal
Crystal class: 4/m 2/m 2/m
Twinning: rare on {031} or {032}, may be polysynthetic
Unit cell: a = 4.400 Å, c = 2.874 Å
Colour: black, dark steel-gray
Diaphaneity:
Luster: metallic, dull
Habit: crystals short to long prismatic, elongated along c-axis, or equant, massive, compact, columnar, fibrous, stalactitic
Hardness: 6 to 6.5
Specific gravity: 5.06
Cleavage: 1; {110} perfect
Tenacity: uneven, brittle
Streak: black, bluish black
Synonyms/varieties: polianite
Comments: trimorphous with ramsdellite and akhtenskite
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