Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
An overview on Sellaite Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of Sellaite gems.
Sellaite Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Sellaite Information
| Data | Value |
| Name | Sellaite |
| Crystallography | Tetragonal: crystals prismatic, acicular, fibrous aggregates. |
| Colors | Colorless, white. |
| Luster | Vitreous. |
| Hardness | 5-5 .5. |
| Density | 3.15. |
| Birefringence | 0.012. |
| Cleavage | Poorly observed although literature indicates perfect in 2 directions. Fracture conchoidal; brittle. |
| Stone Sizes | The Brazilian sellaite is the w0rld‘s only extant cuttable material, and the largest crystals found thus far are only 5 cm long with small transparent areas. Thus, gems of only a few carats have or could be produced. This is an exceedingly rare gemstone, both in occurrence and number of cut stones. |
| Luminescence | None reported. |
| Spectral | None. |
| Formula | MgF2. |
| Pleochroism | None. |
Optics: o=1.378; e= 1.390.
Uniaxial (+).
Occurrence: Sellaite occurs in a wide vaiiety of geologica environments.
Vesuvius, Italy: in volcanic fumaroles.
Harz Mountains, Germany: in evaporite beds.
Italy; France: in veins.
Nertschin, USSR: in pegmatites.
Oslo Region, Norway: cavities in a soda-granite.
Brumado Mine, Bahia, Brazil: gemmy crystals in a metamorphic magnesite deposit.
Name: After the Italian mining engineer and mineralogist, Quintino Sella.
