Mullite

Formula:  Al₆Si₂O₁₃

Origin of name:  After locality; Island of Mull, Scotland

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning: 

Unit cell: a = 7.55 Ǻ, b = 7.69 Ǻ, c = 2.88 Ǻ

Colour:  Colourless to pale pink

Diaphaneity:  Transparent to translucent

Luster:  Vitreous

Habit:  Crystals prismatic

Hardness:  6 to 7

Specific gravity:  3.03 to 3.08

Cleavage:  1; {010} distinct

Tenacity: 

Streak: 

Synonyms/varieties:

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