Formula: SrMn2Si2O7(OH)2 . H2O
Origin of name: For Henno Martin, German geologist who escaped to South Africa from Nazi Germany.
Crystal system: Orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 6.255, b = 9.034, c = 13.397
Colour: Yellow-brown, brown
Diaphaneity: Translucent
Luster: Vitreous
Habit: Poikiloblasts about 1 mm across, rarely in felt-like masses, as irregular aggregates, embedded in other minerals
Hardness: 4
Specific gravity: 3.68
Cleavage: None
Tenacity:
Streak: Yellowish brown
Synonyms/varieties:
Comments:
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