In high-temperature sodic volcanic and hypabyssal rocks.
IMA Status:
Valid Species (Pre-IMA) 1885
Locality:
Rather abundant worldwide. Some localities for well-characterized material include: on Pantelleria and Ustica Islands, Italy. At Larvik, Norway. From Berkum, North Rhine-Westphalia, Ge
Link to MinDat.org Location Data.
Name Origin:
From the Greek for "oblique" and "fracture," descriptive of the cleavage
Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Habit:
Disseminated - Occurs in small, distinct particles dispersed in matrix.
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Hardness:
6 - Orthoclase
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Anorthoclase
Gladstone-Dale:
CI meas= 0.007 (Superior) - where the CI = (1-KPDmeas/KC) CI calc= 0.027 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2001,KPDmeas= 0.2043,KC= 0.2057 Ncalc = 1.53 - 1.54
Optical Data:
Biaxial (-), a=1.519-1.529, b=1.524-1.534, g=1.527-1.536, bire=0.0070-0.0080, 2V(Calc)=64-74, 2V(Meas)=34-60. Dispersion r > v.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Pleochroism (z):
colorless.
Calculated Properties of Anorthoclase
Electron Density:
Bulk Density (Electron Density)=2.56 gm/cc note: Specific Gravity of Anorthoclase =2.59 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEAnorthoclase = 1.98 barns/electron U=PEAnorthoclase x relectron= 5.08 barns/cc.
Radioactivity:
GRapi = 52.50 (Gamma Ray American Petroleum Institute Units)
Concentration of Anorthoclase per GRapi unit = 1.90 (%)
Estimated Radioactivity from Anorthoclase - barely detectable
Chemical Formula: 
- barely detectable