Onyx
black · Chalcedony family
| Also known as | Chalcedony (Chalcedony family) |
|---|---|
| Colour | Black, White, Red, Brown |
| Mohs hardness | 6.5–7 |
| Lustre | Vitreous, silky |
| Streak | White |
| Crystal system | Trigonal (quartz), Monoclinic (moganite) |
| Transparency | Translucent |
| Cleavage | None |
| Fracture | Uneven, conchoidal |
| Chemical formula | SiO 2 (silicon dioxide) |
| Specific gravity | 2.55–2.70 |
What is Onyx?
Onyx is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. Sardonyx is a variety with red to brown bands alternated with black or white bands. The name "onyx" is also frequently used for level-banded (parallel-banded) agates, but in proper usage it refers to color pattern not band structure. Onyx, as a descriptive term, has also been incorrectly applied to parallel-banded varieties of alabaster, marble, calcite, obsidian, and opal, and misleadingly to materials with contorted banding, such as "cave
How to identify Onyx
- Lustre: Vitreous, silky.
- Hardness: Mohs 6.5–7 — about as hard as a steel knife.
- Streak: White.
- Habit: Trigonal (quartz), Monoclinic (moganite) crystal system.
Onyx in different forms
Stones often confused with Onyx
Frequently asked questions
How hard is Onyx?
Onyx is Mohs 6.5–7 on the hardness scale.
What colour is Onyx?
Onyx is typically black, white, red, brown (Black and white; red to brown with black or white (sardonyx)).