General Information:
Chemical Formula:
Be4Si2O7(OH)2
Composition:
(Molecular Weight = 238.23 gm)
Beryllium 15.13 % Be
Silicon 23.58 % Si
Hydrogen 0.85 % H
Oxygen 60.44 % O
Empirical Formula:
Be4(Si2O7)(OH)2
Environment:
Commonly found in Be-bearing pegmatites and may be derived from the alteration of beryl.
Locality:
Discovered at near Nantes, Loire-Inferieure, France. Also found at Irkutka and Altai Mountains, Siberia, Russia.
Name Origin:
Named after the French mineralogist, E. Bertrand.
Physical Properties:
Cleavage:
[001] Perfect, [110] Distinct, [101] Distinct
Color:
colorless or pale yellow.
Density:
2.59 - 2.6, Average = 2.59
Diaphaniety:
Translucent to transparent
Habits:
Crystalline - Fine - Occurs as well-formed fine sized crystals., Tabular - Form dimensions are thin in one direction., Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline ).
Hardness:
6-7 - Orthoclase-Quartz
Luminescence:
None.
Luster:
Vitreous (Glassy)
Streak:
white
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