Formula: NaCaAlF6.H2O
Origin of name: For Hans Peter Jorgen Julius Thomsen (1826-1909), Daniosh physical chemist and founder of the Greenland cryolite industry.
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell: a = 5.57, b = 5.5, c = 16.1, β = 96.383°
Colour: Colourless, white, reddish or brownish from hematite inclusions
Diaphaneity: Transparent to translucent
Luster: Vitreous, somewhat pearly on cleavage
Habit: Crystals prismatic parallel [001], tabular on{001} or often nearly cubic through development of {001} and {110}, rarely spherulitic, massive, stalactitic, chalcedonic crusts
Hardness: 2
Specific gravity: 2.98
Cleavage: 2; {001} perfect, {110} distinct
Tenacity: Brittle, uneven fracture
Streak: White
Synonyms/varieties:
Comments: dimorphous with pachnolite. Alteration product of cryolite.
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