Demantoid Garnet
Demantoid is just a variety of Andradite Garnet which is really a known member of this Garnet Group of minerals that includes Almandine, Andradite, Grossular, Pyrope, Spessartine and Uvarovite. All Garnets fall into these varieties which are basic some Garnets are a definite combination of two. The Garnets are a definite family that is complex of all with similar crystalline structures but varying greatly in chemical structure and properties. Demantoid is from the Andradite variety and is colored deep green by chromium. Topazolite may be the variety that is yellow of Garnet. The dispersion of Andradites could be the greatest of all of the Garnets and gems of this variety have a fire that is tremendous. Demantoid from Russia is identified by its “horse-tail” inclusions of byssolite (fibrous amphibole). Demantoid is available from several sources across the international world but many prized from the Urals Region of Russia.
Demantoid Garnet was named by Nils Gustaf Nordenskiøld from the archaic word that is germanDemant” which means “diamond” in allusion to its quite high brilliance resembling that of a diamond. The name Andradite is named after the mineralogist that is Brazilian Bonifácio de Andrada e Silva (1763-1838) (1763-1838). The name Garnet comes from the Latin word granatus meaning grain. This is the contrast of garnet grains in rock looking just like the deep red seeds of the Pomegranite good fresh fruit scattered on the floor.
| Category: | Mineral |
| Chemical Formula: | Ca3Fe2(SiO4) Calcium chromium silicate |
| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | Commonly well-crystallized dodecahedra, trapezohedra, or combinations, to 5 cm. Also granular to massive. |
| Twinning: | None |
| Cleavage: | None |
| Fracture: | Uneven to Conchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 6.5 – 7.0 |
| Density: | 3.82 – 3.89 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Greenish Yellow, Green, Emerald Green, Dark Green |
| Transparency: | Transparent, Translucent |
| Luster: | Adamantine, Resinous, Dull |
| Refractive Index: | 1.887 Isotropic |
| Birefringence: | 0.000 (Isotropic) |
| Dispersion: | 0.057 (high) |
| Pleochroism: | None |
| Other: | Weakly Anisotropic |
