THE MATERIAL LIBRARY
Onyx
In gemological usage, parallel-banded chalcedony.
Colors & patterns
Black and white bands are familiar; solid black commercial onyx is commonly treated.
Typical origins
Chalcedony sources include Brazil, India and Uruguay.
Hardness
6.5–7 for chalcedony on the Mohs scale.
Choosing & setting this material
Confirm that a product is chalcedony. Decorative stone sold as onyx marble is usually calcite-rich and has different hardness and care requirements.
Care & cleaning
Clean gently with lukewarm water, a little mild soap and a soft cloth, then dry. Avoid steam, ultrasonic cleaners, harsh chemicals and sudden temperature changes, especially when treatments are unknown.
Origins above describe typical sources of the material, not the origin of an illustrated or stocked stone. Hardness measures scratch resistance, not resistance to breaking. Confirm the identity and treatments of the actual piece.
Further reading: Material reference · GIA: gem treatments