Egyptian Revival, Victorian Scarab Brooch, c.1870.
Egyptian Revival, Victorian Labradorite Scarab Brooch, c.1870.

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
Hardness:6 to 6.5
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.
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