General Information:
Chemical Formula:
Al2SiO4(F,OH)2
Composition:
(Molecular Weight = 182.25 gm)
Aluminum 29.61 % Al
Silicon 15.41 % Si
Hydrogen 0.50 % H
Oxygen 43.02 % O
Fluorine 11.47 % F
Empirical Formula:
Al2(SiO4)F1.1(OH)0.9
Environment:
Pegmatites and high temperature quartz veins. Cavities in granites and rhyolites.
Locality:
Topasos Island in the Red Sea.
Name Origin:
Named after its locality.
Physical Properties:
Cleavage:
[001] Perfect
Color:
colorless, pale blue, yellow, yellowish brown, or red.
Density:
3.5 - 3.6, Average = 3.55
Diaphaniety:
Transparent
Habits:
Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Massive - Granular - Common texture observed i n granite and other igneous rock.
Hardness:
8 - Topaz
Luminescence:
Fluorescent, Short UV=golden yellow, Long UV=cream.
Luster:
Vitreous (Glassy)
Streak:
white
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