Sard
Rock / aggregate
Sard is brownish-red chalcedony. It is a polycrystalline material rather than a single mineral species; its dominant component is Quartz.
Photos
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About Quartz
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Quartz species page.
| Formula | SiO2 |
|---|---|
| Hardness (Mohs) | 7 |
| Specific gravity | 2.6-2.64 |
| Density (calculated) | 2.65 |
| Crystal system | trigonal |
| Color range | black, blue, brown, colorless, green, red, yellow |
| Luster | dull, greasy, vitreous |
| Streak | white |