Sardonyx
What is Sardonyx?
Sardonyx is a variant of onyx, which is itself a variety of chalcedony. Sardonyx is characterized by its layers of sard and onyx, showing contrasting bands of colors like red, white, and brown. It’s primarily found in India, Brazil, and Uruguay.
Sardonyx is a unique gemstone that comes in layers of contrasting colors, often including red, white, and brown. Its banded appearance makes it a popular choice for cameos, beads, and other ornamental uses.
| Chemical Classification | Inorganic - Silicate (Chalcedony) |
| Color | Sardonyx displays alternating bands of reddish-brown sard and black, white, or clear onyx. |
| Streak | White |
| Luster | Waxy to vitreous. |
| Transparency | Opaque. |
| Occurrence | India, Brazil, and Uruguay. |
| Formation | Sardonyx forms in hydrothermal veins and in cavities in volcanic rocks. |
| Diaphaneity | Translucent to opaque |
| Cleavage | None |
| Mohs Hardness | 6.5 to 7. |
| Specific Gravity | 2.58-2.64. |
| Diagnostic Properties | Banded red and white chalcedony. |
| Chemical Composition | SiO2 |
| Pleochroism | None. |
| Crystal System | Hexagonal (variety of Quartz) |
| Optical Properties | Uniaxial (+) |
| Refractive Index | 1.530 - 1.539 |
| Birefringence | 0.009 |
| 2V angle | Not applicable (isometric) |
| Dispersion | Not notably high. |