Formula: (Mn,Ca,Mg)Mn3O7.H2O
Origin of name: after locality Todoroki mine, Hokkaido, Japan
Crystal system: Monoclinic
Crystal class: 2/m
Twinning: As contact twins or trillings on an unknown law
Unit cell: a = 9.764, b = 2.842, c = 9.551, β = 94.14°
Colour: Dusky purplish gray, dark brown to dark brownish black, sooty black
Diaphaneity: Opaque, transparent in thinnest slivers
Luster: Metallic to dull, silky in aggregates
Habit: crystals poor, thin plates, minute, nodular masses, columnar to fine fibrous aggregates, stalactitic, thin coatings
Hardness: Soft
Specific gravity: 3.66
Cleavage: 2; {100} and {010} perfect
Tenacity:
Streak: Black, dark brown
Synonyms/varieties:
Comments: Primarily found as a constituent mineral in deep sea nodules.
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