General Information:
Chemical Formula:
NaCa4[Al8Si28O72·n(H2O) (n=28-32)
Composition:
(Molecular Weight = 2,877.96 gm)
Sodium 0.80 % Na
Calcium 5.57 % Ca
Aluminum 7.50 % Al
Silicon 27.32 % Si
Hydrogen 2.10 % H
Oxygen 56.70 % O
Empirical Formula:
NaCa4Al8Si28O72·30(H2O)
Environment:
Amygdaloidal cavities in basalts and similer rocks.
Locality:
Trentino, Italy.
Name Origin:
From the Greek stilbe - "luster" in allusion to the pearly to vitreous luster.
Physical Properties:
Cleavage:
[010] Perfect
Color:
white, red, yellow, brown, or cream.
Density:
2.1 - 2.2, Average = 2.15
Diaphaniety:
Transparent to Subtransparent to translucent
Habits:
Wheat Sheaf - Bundle shaped aggregates resembling wheat sheafs after hand reaping wheat., Fibrous - Crystals made up of fibers., Globular - Spherical, or nearly so, rounded forms (e.g . wavellite).
Hardness:
3.5-4 - Copper Penny-Flourite
Luminescence:
None.
Luster:
Vitreous - Pearly
Streak:
white
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