General Information:
Chemical Formula:CaAl2Si2O8
Composition:(Molecular Weight = 277.41 gm)Sodium 0.41 %
NaCalcium 13.72 %
CaAluminum 18.97 %
AlSilicon 20.75 %
SiOxygen 46.14 %
O Empirical Formula: Na0.05Ca0.95Al1.95Si2.05O8
Environment:Magmatic and metamorphic rocks.
Locality:Monte Somma and Valle di Fassa, Italy.
Name Origin:From the Greek, an + orthos, "not upright" in allusion to the oblique crystals.
Physical Properties: Cleavage:[001] Perfect, [010] Good
Color:colorless, gray, white, red, or reddish gray.
Density:2.72 - 2.75, Average = 2.73
Diaphaniety:Transparent to Subtransparent to translucent
Habits:Granular - Generally occurs as anhedral to subhedral crystals in matrix., Euhedral Crystals - Occurs as well-formed crystals showing good external form., Striated - Parallel lines on crystal surface or cleavage face.
Hardness:6 - Orthoclase
Luminescence:None.
Luster:Vitreous (Glassy)
Streak:white
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