Anatase
Anatase is a gem that is very rare because crystals are usually really dark, seldom transparent and tiny. Anatase has very dispersion that is high RI, but its dark colour often masks these. Lighter gems that are coloured quite bright and breathtaking and among the rarest of all of the gems. Anatase is certainly one of the three types of Titanium Dioxide found as gemstones. One other two are Brookite and Rutile. This means that the three minerals have the chemistry that is exact same TiO2, but they have various structures.
Anatase is really a very mineral that is wide-spread but just a few occurrences could be noted. In Alpine veins at many localities throughout the Swiss, French, and Italian and Tirolian Alps: big crystals from Binn, Valais, and at Cavradi, Tavetsch, Graubünden, Switzerland. From LaGrave, Hautes-Alpes, and Bourg d’Oisans, Isère, France. In Norway, at Kragerø; fine crystals from Hardangervidda, Ullensvang; Slidre, Valdres; and Gudbrandsdalen. From the Khorovod Mountains, Sakha, Russia. In the Lady that is virtuous mine Devonshire, England. At Fron Oleu, near Tremadog, Gwynedd, Wales. In several carbonatite deposits, aggregating 500 million tonnes, in Minas Gerais and Pará, Brazil. In the United States, at many localities in Burke County, North Carolina; Buckingham County, Virginia; from Quincy, Norfolk County, Massachusetts; at Placerville, Eldorado County, California. In Canada, at Sherbrooke Township, Nova Scotia, plus in Henry Township, Ontario.
| Category: | Oxide minerals |
| Chemical Formula: | TiO2 |
| Titanium Oxide | |
| Molecular Weight: | 79.88 gm |
| Composition: | Titanium | 59.94 % | Ti | 100.00 % | TiO2 |
| Oxygen | 40.06 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Tetragonal – Ditetragonal Dipyramidal |
| Crystal Habit: | Crystals typically acute dipyramidal, often highly modified; obtuse pyramidal or tabular; less commonly prismatic, to 3.75 cm. |
| Twinning: | Rare on {112} |
| Cleavage: | Perfect on {001} and {011} |
| Fracture: | Sub-Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.5 – 6.0; VHN = 616–698 (100 g load) |
| Density: | 3.82 – 3.97 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Colour: | Brown, Pale Yellow or Reddish Brown, Indigo, Black; Pale Green, Pale Lilac, Gray, rarely nearly Colourless; Brown, Yellow-Brown, Pale Green, Blue in transmitted light. |
| Transparency: | Transparent when the light coloured, to nearly opaque when deeply coloured. Pyramidal crystals may appear opaque because of total reflection. |
| Luster: | Adamantine to Splendent, Metallic |
| Refractive Index: | 2.488 – 2.564 (very high) Uniaxial ( – ) anomalously biaxial in deeply colored crystals |
| Birefringence: | 0.046 – 0.067 |
| Dispersion: | 0.213 – 0.259 (very high) |
| Pleochroism: |
Weak; stronger in deeply colored crystals |
