| Property |
Specification |
| Chemical Composition |
Sodium aluminum silicate with sulfur (Na8(Al6Si6O24)S2) |
| Color |
Deep blue, with golden pyrite inclusions |
| Hardness |
5 to 5.5 on the Mohs scale |
| Specific Gravity |
2.7 to 2.9 g/cm³ |
| Transparency |
Opaque |
| Luster |
Vitreous to sub-metallic |
| Texture |
Rough, uneven, often granular |
| Crystal Structure |
Massive, granular, occasionally columnar |
| Cleavage |
None |
| Fracture |
Conchoidal |
| Density |
2.7 – 2.9 g/cm³ |
| Refractive Index |
1.5 to 1.7 |
| Streak |
Pale blue to white |
| Associated Minerals |
Pyrite, Calcite, and other minerals |
| Origin |
Afghanistan, Chile, Russia, USA, and others |
| Uses |
Jewelry, carvings, ornamental stones |
