Formula: BeAlSiO4(OH)
Origin of name: From Greek for good and fracture
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell: a = 4.76 Ǻ, b = 14.29 Ǻ, c = 4.62 Ǻ, β = 100.3°
Colour: Colourless, whitish, pale green, pale blue
Diaphaneity:
Luster: Vitreous
Habit: Crystals long prismatic, or short and stout prismatic
Hardness: 7.5
Specific gravity: 3.05 to 3.10
Cleavage: 3; {010} perfect, {110} and {001} imperfect
Tenacity: Conchoidal; brittle
Streak: White
Synonyms/varieties:
Comments:
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