Formula: KAl2(Si3Al)O10(OH,F)
Origin of name: Form Russian name Muscovy glass
Crystal system: Monoclinic
Crystal class: 2/m
Twinning: On {001} about [310] axis, stellate
Unit cell: a = 5.21 Ǻ, b = 9.00 Ǻ, c = 10.28 Ǻ, β = 101.6˚
Colour: Colourless, gray, green, yellow, brown, violet, rose-red, deep red
Diaphaneity:
Luster: Vitreous to pearly or silky
Habit: Crystals tabular, hexagonal or diamond-shaped cross section; massive, scaly or lamellar; plumose or stellate aggregates
Hardness: 2.5 to 4
Specific gravity: 2.77 to 2.88
Cleavage: 1; {001} perfect
Tenacity: Thin laminae flexible
Streak: Colourless
Synonyms/varieties: Fuchsite/mariposite (Cr-rich variety), sericite (fine grained variety), roscoelite (V-rich variety), phengite (Al-poor variety), alurgite (Mg, Fe,Mn-rich variety), astrolite
Comments:
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