General Information:
Chemical Formula:
SiO2·n(H2O)
Composition:
(Molecular Weight = 87.11 gm)
Silicon 32.24 % Si
Hydrogen 3.47 % H
Oxygen 64.29 % O
Empirical Formula:
SiO21.5(H2O)
Environment:
Sedimentary and secondary from the alteration of high silica igneous extrusive rocks.
Locality:
World wide occurrences.
Name Origin:
From the Old Indian upala - "precious stone."
Physical Properties:
Cleavage:
None
Color:
white, yellow, red, brown, or blue.
Density:
1.9 - 2.3, Average = 2.09
Diaphaniety:
Transparent to translucent to opaque
Habits:
Amorphous - No crystalline form or imitative shape., Massive - Uniformly indistinguishable crystals forming large masses., Reniform - "Kidney like" in shape (e.g.. hematite).
Hardness:
5.5-6 - Knife Blade-Orthoclase
Luminescence:
Fluorescent, Short UV=greenish yellow, Long UV=white.
Luster:
Vitreous - Dull
Streak:
white
More details...