Formula: (Mg,Al)8(Al,Si)6O20
Origin of name: from sapphire
Crystal system: monoclinic
Crystal class: 2/m
Twinning:
Unit cell:
Colour: pale blue to bluish or greenish gray, green
Diaphaneity: transparent
Luster: vitreous
Habit: crystals tabular, granular, disseminated
Hardness: 7.5
Specific gravity: 3.4 to 3.5
Cleavage: 3; {100}, {001} and {010} indistinct
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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