Yellow-green Sanidine crystal from the small finds at Itrongay, Madagascar. Weighs 20 grams or 100 carats. By Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Yellow-green Sanidine crystal from the small finds at Itrongay, Madagascar. Weighs 20 grams or 100 carats. By Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Data | Value |
---|---|
Name | Sanidine |
Is a Variety of | Orthoclase |
Colors | Colorless, sometimes brown or yellow. |
Fracture | Uneven to splintery, Parting common |
Hardness | 6-6.5 |
Cleavage | Perfect and easy in two directions |
Wearability | Poor |
Crystallography | Monoclinic. |
Refractive Index | 1.516-1.526 |
Birefringence | 0.003-0 .007 |
Dispersion | None. |
Luminescence | None. |
Luminescence Present | No |
Absorption Spectrum | Not diagnostic. |
Pleochroism | None. |
Optics | Biaxial (-). 2V = 18-54º. |
Optic Sign | Biaxial - |
Luster | Vitreous. |
Specific Gravity | 2.57-2.58 |
Transparency | Transparent to translucent. |
Comments
Sanidine is a mineral of volcanic rocks, with little gem significance. It is uncommon and rarely seen as a gem. While occasionally brown or yellow, most examples are colorless. While the properties are closer to microcline, it is usually classed as a plagioclase.
Name
Sanidine is also from the Greek, sanis, meaning board, in reference to the tabular crystals. Anorthoclase is from Greek words for not upright because the cleavage is not 90°.
Occurrence
Stone Sizes
Sanidine is not a common mineral and is hardly ever seen as a gemstone. Crystals tend to be colorless and nondescript and are rare in cuttable sizes.