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Sanidine is a potassium-rich feldspar which is related to amazonite (microcline) and orthoclase by its chemistry. Sanidine gems that display adularescence, a mystical internal glow, are called moonstone. Colorless to yellow and pale brown gems have been found in Germany, Mexico, and Madagascar.

Sanidine Polished
Sanidine Classification
Common Name Sanidine
Species Feldspar
Sanidine Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: Weak Fire Value: 0.012
Refractive Index 1.518-1.531
Birefringence 0.003-0.007
Optic Character Biaxial
Optic Sign Negative
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert to weak red-orange
LWUV: Inert to weak red-orange
Pleochroism Unobservable
Sanidine Characteristic Physical Properties
Hardness 6-6.5
Streak White
Specific Gravity Typical:2.600
Luster Vitreous
Fracture Conchoidal, Uneven
Cleavage Perfect, in two directions
Sanidine Chemistry & Crystallography
Chemical Name Potassium or Sodium Aluminum Silicate
Chemical Formula (K, Na)(AlSi3O8)

Crystal System Monoclinic
Chemistry Classification Silicate

Sanidine Colors

  • Brown Sanidine Brown
  • Yellow Sanidine Yellow
  • Colorless Sanidine Colorless

Countries of Origin


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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.