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, and sunstone. From the Greek word klasis meaning cleaving (clase) with a cleavage direction as the prefix.
- Microcline
- Orthoclase
- Plagioclase
- Labradorite
- Oligoclase
- Spectrolite (trade name for Labradorite)
- Sunstone (variety of Labradorite or Oligoclase depending on the color)
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 |
| Durability: | Poor |
| Hardness: | 6 to 6.5 |
| Family: | Feldspar |
| 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 |
Sources
- 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.