Sanidine Value, Price, and Jewelry Information

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

Sanidine

Sanidine Information

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

  • A component of acid igneous rocks. Oregon; California.
  • Near Koblenz, Germany: brown transparent gems; S.G. 2.57-2.58; birefringence 0.007; indices: 1.516-1.520/ 1.520-1.525/1.522-1.526.
  • Ashton, Idaho: sanidine crystals in volcanic luff, up to 1 cm, colorless, well formed. Indices: 1.516-1.519/ 1.520-1.522/1.521-1.523; 2V=8-19°; birefringence 0.003-0.005.

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.

by Joel E. Arem, Ph.D., FGA