Judging quality
Bands should be flat and parallel rather than concentric. Much commercial sardonyx is dyed banded agate, which shows unnaturally crisp color boundaries.
Chalcedony
Sardonyx
Straight-banded chalcedony alternating reddish-brown sard with white — the classic cameo material, because a carver can cut through the pale layer to reveal the dark one beneath.
Care
Durable; ordinary cleaning.
History & lore
Roman signet rings in sardonyx were the standard of legal identity, and the Gemma Augustea is carved from a two-layer piece.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Sardonyx
- What is Sardonyx?
- Straight-banded chalcedony alternating reddish-brown sard with white — the classic cameo material, because a carver can cut through the pale layer to reveal the dark one beneath.
- How hard is Sardonyx and what is it made of?
- Sardonyx is a Chalcedony-family mineral with the composition SiO2. It crystallizes in the trigonal system and rates 6.5-7 on the Mohs hardness scale. It occurs in red, white, brown, banded.
- Where does Sardonyx come from?
- Notable localities for Sardonyx include India, Brazil, Germany (Idar-Oberstein), Uruguay.
- How do you tell good Sardonyx from filler?
- Bands should be flat and parallel rather than concentric. Much commercial sardonyx is dyed banded agate, which shows unnaturally crisp color boundaries.
- How do you care for Sardonyx?
- Durable; ordinary cleaning.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.