Carnelian
Chalcedony (quartz)JewelryWiki Editorial·2 sources·Reviewed 2026-08-04
Translucent orange to reddish-brown chalcedony, one of the oldest gem materials in continuous use — it was carved into seals and signet rings in antiquity precisely because hot wax does not stick to it. Much modern carnelian is heat-treated or dyed agate.
Properties
| Property | Value | Authority |
|---|---|---|
| Mohs hardness | 7 [1] | — |
| Specific gravity | 2.55–2.91 [1] | — |
| Chemical formula | SiO2 Read from the species entry, Chalcedony. A variety shares its species’ formula. [2] | — |
| Crystal system | Hexagonal (trigonal), microcrystalline [1] | — |
| Common treatments | Dyeing is listed by IGS among chalcedony’s typical treatments, and heating is widely used to deepen orange to red. A very even, saturated colour is a sign of treatment; natural carnelian is usually cloudier and less uniform. [1] | — |
| Care cautions | Hard enough for daily wear at Mohs 7. If dyed, keep away from solvents and prolonged sunlight. [1] | — |
Sources
- International Gem Society — gemstone articles — International Gem Society (IGS, gemstone information articles (gemsociety.org))
- Handbook of Mineralogy — Mineral Data Publishing / Mineralogical Society of America (Handbook of Mineralogy, Mineral Data Publishing)