Sphene (Titanite)
Titanite (also known as Sphene) is a beautiful gem with high dispersion, high refractive index (greater than Diamond), high birefringence and intense red, green and yellow colors. Unfortunately, it also has low hardness and is brittle so not recommenced for jewelry. Titanite is typically slightly to moderately included and clean gems are particularly rare and beautiful. Titanite may be mildly radioactive as defined in 49 CFR 173.403 (greater than 70 Bq/gram) due to the presence of the Rare Earth Elements (REE) Cerium (Ce), Lanthanum (La), Neodymium (Nd), Praeseodymium (Pr) and Samarium (Sm). Titanite may also be metamict. This means that the original crystal structure has been broken down and turned amorphous due to radiation damage. An intensly vivid green, chromium (Cr) rich variety of Titanite exists called Chromian Titanite. The main source of Chromian Titanite is the Saranovskii Mine, Saranovskaya Village, Gornozavodskii area, Permskaya Oblast’, Middle Urals Region, Russia.
Notable occurances of gemmy crystals of Titanite include Gilget and Badakhshan Provinces, Afghanistan; Pi~no Solo. From Campo do Boa, Capelinha, Minas Gerais, Brazil; Antsiranana and Tuléar Provinces, Madagascar; Skardu District, Baltistan, Northern Areas, Pakistan; and Subpolar Ural Mountains, Russia.
| Chemical Formula: | CaTiSiO5 |
| Calcium Titanium Silicate | |
| Molecular Weight: | 197.76 gm |
| Composition: | Calcium | 19.25 % | Ca | 26.94 % | CaO |
| La,Ce,Pr,Nd,Sm | 3.64 % | RE | 4.25 % | REE2O3 | |
| Titanium | 18.16 % | Ti | 30.29 % | TiO2 | |
| Aluminum | 2.73 % | Al | 5.16 % | Al2O3 | |
| Iron | 1.41 % | Fe | 2.02 % | Fe2O3 | |
| Silicon | 14.20 % | Si | 30.38 % | SiO2 | |
| Oxygen | 39.64 % | O | |||
| Fluorine | 0.96 % | F | 0.96 % | F | |
| — | — % | F | -0.40 % | -O=F2 | |
| 100.00 % | 99.60 % | = TOTAL OXIDE | |||
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals wedge-shaped, flattened or prismatic by extension along [110], to 16 cm; compact, massive |
| Twinning: | On [100], contact and penetration; less commonly lamellar on [221] |
| Cleavage: | Distinct on [110], Imperfect on [100] and [112]; parting due to twinning on [221] |
| Fracture: | Sub-Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.0 – 5.5 |
| Density: | 3.48 – 3.60 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Mild; GRapi = 3,805.77 (Gamma Ray American Petroleum Institute Units) |
| Other: | May be metamict |
| Color: | Colorless, Reddish Brown, Red, Yellow, Green, Gray, Black |
| Transparency: | Transparent to Translucent, Opaque |
| Luster: | Adamantine to Resinous |
| Refractive Index: | 1.843 – 2.110 Biaxial ( + ) |
| Birefringence: | 0.100 – 0.160 (high) |
| Dispersion: | Extreme; r > v |
| Pleochroism: | Visible; distinct when deeply colored; X = nearly colorless; Y = yellow to green; Z = red to yellow-orange |
