Stilbite
Stilbite is a member of the Zeolite Group of minerals that includes over 40 minerals and these gem-type minerals: Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite-Na, Goosecreekite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite and Yugawaralite. Stilbite is not a rare mineral but it is rarely available as a faceted or cabochon gem because it’s rarely transparent enough. Cabochon gems do have a beautiful chatoyance and pearly luster and creamy orange gems are particularly beautiful. It is available from many sources worldwide but exceptional crystals from the Bombay, Poona, and Nasik districts, Maharashtra, India.
| Category: | Tectosilicate, Zeolite |
| Formula: | Stilbite-Ca: NaCa4(Si27Al9)O72·28(H2O) Stilbite-Na: Na9(Si27Al9)O72·28(H2O) |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals typically thin tabular, to 14 cm; in fibrous, sheaf-like or globular aggregates. Twinning: Cruciform and Penetration twins. |
| Cleavage: | [010] Perfect |
| Fracture: | Concoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 3.5 – 4.0 |
| Density: | 2.10 – 2.20 (g/cm3) |
| Radioactivity: | Not Radioactive |
| Color: | White, Colourless, Red, Light Yellow, Light to Dark Brown, Cream, Orange, Pink |
| Transparency: | Transparent to Translucent, Opaque |
| Luster: | Vitreous, Pearly |
| Refractive Index: | 1.479 – 1.505 Biaxial ( – ) |
| Birefringence: | 0.0100 – 0.0130 |
| Dispersion: | Weak |
| Pleochroism: | None |
