Phenakite
Phenakite is a rare beryllium silicate mineral that is often found in pegmatitic pockets associated with other gem minerals such as Topaz, Emerald, Chrysoberyl and Smoky Quartz. the chemical formula of Phenakite is Be2SiO4 (Beryllium Silicate) and its molecular weight is 110.11 gm. Phenakite is a beautiful gem that is ideal for use in jewelry because of its high hardness (7.5 – 8.0) and bright white color. Phenakite has a specific gravity of 2.93 – 3.00 (g/cm3) and the refractive index of 1.650 – 1.670 Uniaxial ( + ). Cut gems have little fire but are very bright. Red Phenakite gems from Russia are known but are very rare. Small gem quality crystals have been found on Pike’s Peak and Mount Antero in Colorado, USA.
Phenakite is one of the few silicate minerals that have a trigonal symmetry. This symmetry is far more common among carbonates than among silicates. Phenakite shares the same symmetry with the emerald green silicate Dioptase and the fluorescent and closely related Willemite.
Distribution: Numerous localities; some for fine crystals are: along the Tokovaya River, near Yekaterinburg (Sverdlovsk), Ural Mountains, and at Miass, Ilmen Mountains, Southern Ural Mountains, Russia. At several places around Kragerö, Norway. In France, in the Vosges Mountains, at Framont, Alsace. From near Reckingen, Valais, and many other places in Switzerland. At Leckbachrinne, Habachtal, Salzburg, Austria. In the USA, from near Florissant, El Paso County, and on Mt. Antero, Cha®ee County, Colorado; on Bald Face Mountain, North Chatham, Carroll County, New Hampshire; at Amelia, Amelia County, Virginia. In Brazil, exceptional crystals in the São Miguel de Piracicaba pegmatite, 50 km east of Belo Horizonte, and at Catuqi, Minas Gerais; in the Socotó mine, northwest of Salvador, Bahia, and elsewhere. At Klein Spitzkopje, Namibia. From Anjanabonoina, Madagascar.
| Category: | Nesosilicate |
| Chemical Formula: | Be2SiO4 |
| Beryllium Silicate | |
| Molecular Weight: | 110.11 gm |
| Composition: | Beryllium | 16.37 % | Be | 45.43 % | BeO |
| Silicon | 25.51 % | Si | 54.57 % | SiO2 | |
| Oxygen | 58.12 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Trigonal – Rhombohedral |
| Crystal Habit: | Crystals rhombohedral, tabular to prismatic, less commonly long prismatic to acicular, to 20 cm. In columnar aggregates, as spherulites, and granular. |
| Twinning: | Penetration twins, by rotation about [0001] |
| Cleavage: | Distinct on {1120}, Imperfect on {1011} |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 7.5 – 8.0 |
| Density: | 2.93 – 3.00 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Colorless, White, Yellow, Pink, Brown; may be mottled |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.650 – 1.670 Uniaxial ( + ) |
| Birefringence: | 0.0170 |
| Dispersion: | 0.005 (weak) |
| Pleochroism: | Only observed in strongly colored crystals |
