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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.