Haüyne

Formula:  Na₃Ca(Si₃Al₃)O₁₂(SO₄)

Origin of name:   For Abbe Rene Hauy, French crystallographer

Crystal system:  Cubic

Crystal class:  -43m

Twinning:  Common on {111}, rarely as penetration; also polysynthetic or contact

Unit cell: a = 9.082 Ǻ

Colour:  Blue, white, gray, green, yellow, red

Diaphaneity: 

Luster:  Vitreous to greasy

Habit:  Crystals dodecahedral or octahedral; rounded grains

Hardness:  5.5 to6

Specific gravity:  2.44 to 2.50

Cleavage:  1; {110} distinct

Tenacity:  Brittle

Streak:  Bluish to colourless

Synonyms/varieties:  Hauynite

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