Feldspar var. Moonstone.

Feldspar is a gem group that includes microcline, orthoclase, and plagioclase varieties. Each variety varies as to crystal structure, refractive index, color and other specifics. Gemstones include: amazonite, moonstone, labradorite, sunstone. From the Greek word klasis meaning cleaving (clase) with a cleavage direction as the prefix.

Gemological Information for Feldspar

Color:Light Green, Greenish Blue, White for Microcline, Green, Colorless, White, Yellow, Brown, Gray and Black for Orthoclase, Gray to Black for Labradorite, Orange, Brown, Colorless for Oligoclase
Crystal Structure:Triclinic (microcline) Monoclinic (orthoclase and plagioclase)
Refractive Index:1.522 to 1.530 (microcline) 1.518 to1.526(orthoclase) 1.599 to 1.568 Labradorite, 1.537 to 1.547 Oligoclase
Hardness:6 to 6.5
Similar Stones:Aventurine Quartz, Chalcedony, Turquoise
Treatments:Wax Impregnation, Irradiation
Country of Origin:Worldwide Deposits

Feldspar 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.