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Armbruster T , Oberhansli R , American Mineralogist , 73 (1988) p.595-600, Crystal chemistry of double-ring silicates: Structures of sugilite and, brannockite, Note: x-coordinate of Na has been corrected
Physical Properties of Sugilite
Cleavage:
{0001} Indistinct
Color:
Brownish yellow, Violet, Reddish violet, Pale pink.
Density:
2.74
Diaphaneity:
Transparent to Translucent
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Habit:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Hardness:
6-6.5 - Orthoclase-Pyrite
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Sugilite
Dichroism (e):
pink.
Dichroism (w):
pale pink.
Gladstone-Dale:
CI meas= 0.064 (Fair) - where the CI = (1-KPDmeas/KC) CI calc= 0.1 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2082,KPDmeas= 0.2166,KC= 0.2314 Ncalc = 1.63 - 1.66