Formula: (Ca,Th,Mn)3Si4O11F.6H2O
Origin of name: From thorium and steenstrupine
Crystal system: amorphous (metamict due to radiation damage)
Crystal class: -
Twinning:
Unit cell:
Colour: Dark brown, nearly black
Diaphaneity: Opaque, translucent in splinters
Luster: Greasy to vitreous
Habit: Crystals platy, rough faces, 2 to 5 mm, uncommon to 1 cm
Hardness: about 4
Specific gravity: 3.02
Cleavage:
Tenacity: Brittle, conchoidal fracture
Streak: Dark brown
Synonyms/varieties:
Comments: Weakly magnetic, radioactive
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