Formula: (Na,K)ThSi11(O,F,OH)25.8H2O
Origin of name: from elements in composition (Th, Na, Si)
Crystal system: Hexagonal, metamict (amorphous due to radiation damage)
Crystal class: 32 or 3m
Twinning:
Unit cell: a = 29.124, c = 17.2602
Colour: colourless, white to pale green, beige
Diaphaneity: Opaque to transparent
Luster: Vitreous to waxy or greasy, may be pearly
Habit: Anhedral to parallel prismatic crystals, to 1.5 mm
Hardness: n.d.
Specific gravity: 2.62
Cleavage:
Tenacity: Brittle, subconchoidal to uneven fracture
Streak: White
Synonyms/varieties:
Comments: Fluoresces bright apple green under LW and SW ultraviolet light, slightly metamict. Pyroelectric, radioactive
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