Formula: Na(Al,Fe)Si2O6
Origin of name: From Spanish, piedra de yjada = stone of the side
Crystal system: Monoclinic
Crystal class: 2/m
Twinning: On {100} or {001}, simple or lamellar
Unit cell: a = 9.44 Ǻ, b = 8.57 Ǻ, c = 5.23 Ǻ, β = 107.6°
Colour: Crystals colourless with green tips; massive in many colours
Diaphaneity:
Luster: Vitreous, massive is greasy to vitreous
Habit: Crystals elongated prismatic, small, rare; massive fine granular to coarse granular; as small to large alluvial boulders
Hardness: 6
Specific gravity: 3.25
Cleavage: 1; {110} good
Tenacity: Tough when massive
Streak: Colourless
Synonyms/varieties: Chloromelanite (compact dark green to black var.), feitsui, imperial jade (compact translucent emerald-green gem var.), jade (compact gem var.)
Comments:
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