Orthoclase is a mineral series in the feldspar group.
- Moonstone
- Colorless
- Yellow
Colorless orthoclase is a pegmatitic gemstone found in igneous rocks. It is also found in metamorphic rock such as schist and gneiss. Commonly mined in Madagascar. Yellow orthoclase is a fragile sone colored by iron. It can be cut en cabochon to exhibit the cat’s-eye phenomenon. Moonstone is the most popular form of orthoclase feldspar and is the one most often found in jewelry.
Gemological Information for Orthoclase Feldspar
| Color: | Colorless, White, Green, Orange, Yellow, Brown, Gray and Black |
| Crystal Structure: | Monoclinic |
| Refractive Index: | 1.518 to 1.526 |
| Durability: | Not Very Durable |
| Hardness: | 6 to 6.5 |
| Family: | Feldspar |
| Similar Stones: | Chalcedony and Quartz |
| Treatments: | Blue or Black Coating on Reverse |
| Country of Origin: | Sri Lanka, Myanmar, India |
Orthoclase Feldspar Care
| Ultrasonic Cleaning: | Never |
| Steam Cleaning: | Never |
| Warm Soapy Water: | Safe |
| Chemical Attack: | Hydrofluoric Acid |
| Light Sensitivity: | Stable |
| Heat Sensitivity: | Can Crack or Cleave when Heated |
Related Reading
Sources
- Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 103-105.
- Hall, Cally. Gemstones, Smithsonian Handbooks. London, DK Penguin Random House, 2021.
Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 164.