Dunilite
Dunilite is just a rare member of the Olivine Group that features Dunilite, Fayalite, Forsterite and Peridot (Olivine) although Peridot is not recognized as a mineral that is separate. Dunilite is a very rare and recently discovered variety of Olivine that had been found in 1996 in gem gravels at Katukubura hill, Kolonne, Sri Lanka it was initially thought to be a color variation of Peridot, and later determined to be a gem variety that is new. The RI values of Dunilite are very different from those of Peridot in addition to the dichroic color distinctions with Peridot. The GIA issued their report on Dunilite in 1998.
| Crystallography: | Orthorhombic – Dipyramidal |
| Crystal Habit: | Crystals are tabular, flattened, rectangle shape corners often modified by a six-sided rhomb shape crystal faces. |
| Cleavage: | [001] Good, [010] Distinct |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.5 |
| Density: | 3.48 (g/cm3) |
| Radioactivity: | Not Radioactive |
| Color: | Greenish Yellow |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.677 – 1.718 Biaxial ( – ) |
| Birefringence: | 0.041 |
| Dispersion: | Relatively Weak |
| Pleochroism: | Strong : Brownish Yellow/ Greenish Yellow |
