Formula: Ba9Fe2Ti2(SiO3)12(OH,Cl,F)6.6H2O
Origin of name: for John Boardman Trask (1824-1879), first state geologist of California, U.S.A.
Crystal system: Hexagonal
Crystal class: 6m2
Twinning:
Unit cell: a = 17.98, c = 12.33
Colour: Brownish red
Diaphaneity: Transparent to translucent
Luster: Vitreous
Habit: Rarely euhedral pyramidal crystals , commonly equant anhedral grains, to 3 mm
Hardness: about 5
Specific gravity: 3.71
Cleavage: None
Tenacity: Conchoidal fracture
Streak: Pale reddish brown
Synonyms/varieties:
Comments: Found in sanbornite-bearing metamorphic rocks along a granodiorite contact.
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