Sardonyx
Named after its ancient place of origin, Sardis, it is an agate derived from sard (originally brownish) that features white banding. In ancient Rome, it was frequently used for cameos and intaglios that took advantage of its stripes.
The contrast between white bands and reddish-brown to orange
Basic Information
| English Name | Sardonyx |
|---|---|
| Japanese Name | Beni-shima Menou (Red Striped Agate) |
| Chemical Composition | SiO2 (cryptocrystalline) |
| Crystal System | Hexagonal (cryptocrystalline) |
| Hardness | 7 |
| Specific Gravity | Approx. 2.60 |
Classification, Treatment, and Related
- Sardonyx with dark red lines, or carnelian sardonyx with orange-red carnelian bands.
- Treatment: Dyeing by long-term immersion in iron salt solutions followed by heating is common.
- Related Techniques: Etched agate (originating in ancient Mesopotamia). Caustic soda is used to partially bleach iron content to create white patterns. Currently produced in Germany and China as well.
- Cameo/Intaglio: General terms for relief carving and sunken carving, respectively. Materials are considered higher quality the purer white their white bands are.
※Related materials: chalcedony and agate.