General Information:
Chemical Formula:
Al6.5-7(BO3)(SiO4)3(O,OH)3
Composition:
(Molecular Weight = 630.73 gm)
Aluminum 29.94 % Al
Silicon 13.36 % Si
Boron 3.43 % B
Oxygen 53.27 % O
Empirical Formula:
Al7O3(BO3)(SiO4)3
Environment:
Pegmatites, pneumatolytic, and metamorphic rocks.
Locality:
San Diego Co., California.
Name Origin:
Named after the French paleontologist, M. E. Dumortier (1803-1873).
Physical Properties:
Cleavage:
[100] Good, [110] Indistinct
Color:
blue, brown, violet, greenish blue, or pink.
Density:
3.3 - 3.4, Average = 3.34
Diaphaniety:
Transparent to translucent
Habits:
Columnar - Forms columns, Fibrous - Crystals made up of fibers., Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Hardness:
8.5 - Chrysoberyl
Luminescence:
None.
Luster:
Vitreous (Glassy)
Streak:
white
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