General Information:
Chemical Formula:
(Na,Ca)(Si,Al)4O8
Composition:
(Molecular Weight = 270.77 gm)
Sodium 4.25 % Na
Calcium 7.40 % Ca
Aluminum 9.96 % Al
Silicon 31.12 % Si
Oxygen 47.27 % O
Empirical Formula:
Na0.5Ca0.5Si3AlO8
Environment:
Igneous and metamorphic rocks.
IMA Status:
Not IMA Approved
Locality:
Common world wide occurrences.
Name Origin:
From the Greek plagios - "oblique" and klao - "I cleave" in allusion to the obtuse cleavage angles of the good cleavages.
Physical Properties:
Cleavage:
[001] Good, [010] Good
Color:
white, gray, bluish white, reddish white, or greenish white.
Density:
2.61 - 2.76, Average = 2.68
Diaphaniety:
Transparent to translucent
Habits:
Massive - Granular - Common texture observed in granite and other igneous rock., ,
Hardness:
6-6.5 - Orthoclase-Pyrite
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
More details...