General Information:
Chemical Formula:
(Na,Ca)(Si,Al)4O8
Composition:
(Molecular Weight = 265.42 gm)
Sodium 6.93 % Na
Calcium 3.02 % Ca
Aluminum 12.20 % Al
Silicon 29.63 % Si
Oxygen 48.22 % O
Empirical Formula:
Na0.8Ca0.2Al1.2Si2.8O8
Environment:
Magmatic and pegmatitic rocks.
Locality:
Twedestrand, Norway.
Name Origin:
From the Greek, oligos and kasein, "little cleavage."
Physical Properties:
Cleavage:
[001] Perfect, [010] Good
Color:
brown, colorless, greenish, gray, or yellowish.
Density:
2.64 - 2.66, Average = 2.65
Diaphaniety:
Transparent to Translucent
Habits:
Euhedral Crystals - Occurs as well-formed crystals showing good external form., Granular - Generally occurs as anhedral to subhedral crystals in matrix.,
Hardness:
7 - Quartz
Luminescence:
Fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
More details...