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Plagioclase is a sub-series of the feldspar group.

Gemological Information For Plagioclase

Color: Gray to Black for Labradorite, Yellow, Orange to Brown for Oligolcase
Crystal Structure: Monoclinic
Refractive Index: 1.599 to 1.568 Plagioclase
Durability: Poor
Hardness: 6 to 6.5
Family: Feldspar
Similar Stones:Beryl, Quartz, Scapolite, Goldstone Glass
Treatments: Wax Impregnation, Irradiation
Country of Origin: Brazil, Madagascar, Norway, US, Russia

Plagioclase Care

Ultrasonic Cleaning: Never
Steam Cleaning: Never
Warm Soapy Water: Safe
Chemical Attack: Hydrofluoric Acid attacks quickly. Impurities may react to other acids
Light Sensitivity: Stable
Heat Sensitivity: Can Crack, Fade and Cleave


  • Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 101-107.
  • Newman, Harold. An Illustrated Dictionary of Jewelry, New York: Thames and Hudson, 1981. Pp. 122.
  • Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 164-167.