Brookite
Brookite is an extremely rare gem mainly because crystals are usually very dark colored and transparent only in small, thin fragments. Facet grade crystals are very small and rare and attractive faceted gems are among the rarest of all gems. Brookite is one of the three forms of Titanium Dioxide found in gemstones. The other two are Rutile and Anatase.
Brookite is a widespread mineral, but only a few localities afford fine crystals. At Fron Oleu, near Tremadog, Gwynned, Wales. From Bourg d’Oisans, Isère, France. In Switzerland, in the Maderanthal and Griessertal, Uri, at Salvan, Valais, and elsewhere. In Austria, found near Prägraten and Virgen, Tirol. From Hardangervidda, Norway. In Russia, at Italians, near Miass, Ilmen Mountains, Southern Ural Mountains, and large crystals in the Dodo mine, about 100 km west-northwest of Saranpaul, Subpolar Ural Mountains. In Italy, at Monte Bregaceto, near Genoa, Liguria. In Brazil, in the diamond placers of Bahia and Diamantina, Minas Gerais. In the USA, at Magnet Cove, Hot Spring County, Arkansas; Ellenville, Ulster County, New York; and near Powderhorn, Gunnison County, Colorado.
| 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: | Orthorhombic – Dipyramidal |
| Crystal Habit: | As crystals, to 12 cm, typically tabular and elongated and striated; commonly pyramidal or pseudohexagonal. |
| Twinning: | None |
| Cleavage: | Poor/Indistinct on {120}, in traces on {001} |
| Fracture: | Irregular/Uneven, Sub-conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.5 – 6.0 |
| Density: | 4.08 – 4.18 (g/cm3) |
| Luminescence: | White to grayish white or yellowish white |
| Radioactivity: | Not Radioactive |
| Color: | Light to dark brown, Dark reddish brown, Red, Orange |
| Transparency: | Opaque to translucent, transparent in thin fragments |
| Luster: | Metallic adamantine to submetallic |
| Refractive Index: | 2.583 – 2.741 Biaxial ( + ) |
| Birefringence: | 0.1220 – 0.1570 |
| Dispersion: | 0.131 (very strong) |
| Pleochroism: | Very weak; yellowish, reddish, orange to brown |
