Sardonyx is a brown and white banded variety of onyx primarily used in glyptography.

Antique Victorian Sardonyx Seal Fob.

Gemological Information for Sardonyx

Color:Brown and White Layers
Crystal Structure:Hexagonal (Trigonal)
Refractive Index:1.535 to 1.539
Hardness:6.5 to 7
Similar Stones:Dyed Onyx
Treatments:Dyeing, Heating
Country of Origin:Brazil

Sardonyx Care

Ultrasonic Cleaning:Usually Safe (Watch for Glued Together White and Brown Cameo Imitations)
Steam Cleaning:Usually Safe
Warm Soapy Water:Safe
Chemical Attack:Attacked by Hydrofluoric Acid and Nitric Acid May Remove Dye
Light Sensitivity:Stable
Heat Sensitivity:May Alter Color


  • Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 45-48.
  • Newman, Harold. An Illustrated Dictionary of Jewelry, New York: Thames and Hudson, 1981. Pp. 269.
  • Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 142.