Orthoclase is a mineral series in the feldspar group.

Gemological information

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
Similar Stones Chalcedony and Quartz
Treatments Blue or Black Coating on Reverse
Country of Origin sri Lanka, Myanmar, India
Orthoclase Feldspar Care
Ultrasonic Cleaning Mever
Steam Cleaning Never
Warm Soapy Water Safe
Chemical Attack Hydrofluoric Acid
Light Sensitivity Stable
Heat Sensitivity Can Crack or Cleave when Heated


Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 103-105.

Newman, Harold. An Illustrated Dictionary of Jewelry, New York: Thames and Hudson, 1981. Pp. 224.

Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 164.