Benitoite

Formula:  BaTiSi3O9

Origin of name:  Locality; San Benito Co., California

Crystal system:  Hexagonal

Crystal class:  -6m2

Twinning:  Rare by rotation around [0001] axis, penetration

Unit cell: a = 22.35 Ǻ, c = 21.41 Ǻ

 

Colour:  blue to deep blue, purple, pink, white, or colourless

Diaphaneity: Transparent to translucent

Luster:  Vitreous

Habit:  Crystals generally flattened and triangular, pyramidal or tabular

Hardness:  6 to 6.5

Specific gravity:  3.64 to 3.68

Cleavage:  1 {10-11} indistinct

Tenacity:  Conchoidal to uneven; brittle

Streak:  Colourless

 

Synonyms/varieties:

 

Comments:  Fluoresces bluish under short wavelength ultraviolet. Found in natrolite veins cutting glaucophane schist in serpentine body, in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting serpentinite

 

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