Uvite
Uvite is a rare member of the Tourmaline Group of minerals that includes Achroite, Dravite, Liddicoatite, Povondraite,Rubellite, Schorl and Uvite. Uvite is a magnesium/iron rich member of the Tourmaline Group. Uvite was once considered to be a very rare variety of the Tourmaline Group but has recently become more readily available on the gem and mineral markets. Other more common and more well know Tourmalines are Elbaite (various colors and colorless, lithium rich), Schorl (opaque black, iron rich), Dravite and Liddicoatite. Most colored Tourmaline used as gemstones are Elbaite Tourmaline. Uvite is named for the Type Locality area, Uva Province, Sri Lanka and is available in colors of light to dark green, yellowish brown, red, brown, blackish brown, black, colorless and may be zoned parallel to prism faces.
Distribution: In Uva Province, Sri Lanka. From the Sagaing district, Myanmar (Burma). In the USA, from Franklin and Hamburg, Sussex County, New Jersey; in New York, at Gouverneur, Pierrepont, Dekalb and elsewhere in St. Lawrence County, and at Horicon, Warren County; and from East Hampton, Middlesex County, Connecticut. From Brumado, Bahia, Brazil. At Hnústa, Slovakia.
| Chemical Formula: | (Ca,Na)(Mg,Fe2+)3Al5Mg(BO3)3Si6O18(OH,F)4 |
| Calcium Sodium Magnesium Iron Aluminum Boro-Silicate Hydroxide Fluoride | |
| Molecular Weight: | 970.23 gm |
| Composition: | Sodium | 0.59 % | Na | 0.80 % | Na2O |
| Calcium | 3.10 % | Ca | 4.33 % | CaO | |
| Magnesium | 5.64 % | Mg | 9.35 % | MgO | |
| Aluminum | 13.90 % | Al | 26.27 % | Al2O3 | |
| Iron | 4.32 % | Fe | 5.55 % | FeO | |
| Silicon | 17.37 % | Si | 37.16 % | SiO2 | |
| Boron | 3.34 % | B | 10.76 % | B2O3 | |
| Hydrogen | 0.31 % | H | 2.79 % | H2O | |
| Oxygen | 49.47 % | O | |||
| Fluorine | 1.96 % | F | 1.96 % | F | |
| – % | F | -0.82 % | -O=F2 | ||
| 100.00 % | 98.14 % | = TOTAL OXIDE | |||
| Crystallography: | Trigonal – Ditrigonal Pyramidal |
| Crystal Habit: | Crystals prismatic to equant, may be tabular, pyramidal, in radiating groups, to 15 cm. Cross sections are typically triangular with curved, convex sides. |
| Twinning: | None |
| Cleavage: | Indistinct on {1011} |
| Fracture: | Irregular/Uneven, Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 7.5 |
| Density: | 2.97 – 3.14 (g/cm3) |
| Luminescence: | May fluoresce a weak mustard-yellow under SW UV. |
| Radioactivity: | Not Radioactive |
| Other: | Piezoelectric and Pyroelectric |
| Color: | Light to dark green, yellowish brown, red, brown, blackish brown, black, colorless; may be zoned parallel to prism faces. |
| Transparency: | Semi-Transparent, Translucent, Opaque |
| Luster: | Vitreous, Resinous, Greasy |
| Refractive Index: | 1.637 – 1.668 Uniaxial ( – ) |
| Birefringence: | 0.0180 – 0.0290 |
| Dispersion: | n/a |
| Pleochroism: | Weak; O = pale yellow; E = colorless |
