Formula: MnO(OH)
Origin of name: From composition
Crystal system: Monoclinic
Crystal class: 2/m
Twinning: On {011}, contact or penetration; on {100}, lamellar
Unit cell: a = 8.98 Å, b = 5.28 Å, c = 5.71 Å, β = 90°
Colour: Black to dark steel-gray
Diaphaneity:
Luster: Submetallic to dull
Habit: Crystals short to long prismatic, vertically striated, often grouped in bundles; massive, fibrous to columnar
Hardness: 4
Specific gravity: 4.33
Cleavage: 3; {010} perfect, {110} and {001} imperfect
Tenacity: Uneven; brittle
Streak: Reddish brown to black
Synonyms/varieties:
Comments: Trimorphous with feitknechtite and groutite
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