Thorite

Formula: (Th,U)SiO4

Origin of name: from composition

 

Crystal system: Tetragonal, commonly metamict

Crystal class: 4/m 2/m 2/m

Twinning: Penetration

Unit cell: a = 7.117, c = 6.295

 

Colour: Brownish yellow, yellow to orange-yellow, brownish black to dark brown, reddish

Diaphaneity: Nearly opaque, transparent in thin fragments

Luster: Vitreous to resinous or greasy

Habit: Crystals square prisms, terminated by {111}, pseudo-octahedral, to 8 cm, massive, compact

Hardness: 4.5 (approximate)

Specific gravity: 6.6-7.2

Cleavage: 1, {110} distinct

Tenacity: Brittle, conchoidal fracture

Streak: Light orange to dark brown

 

Synonyms/varieties: Orangite

 

Comments: dimorphous with huttonite, density increases with increase in water content. Radioactive, paramagnetic

 

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