Vesuvianite (Idocrase)
Vesuvianite (also known as Idocrase) is found in colors ranging from green to brown and also a blue variety called Cyprine. The complexities of its chemistry leads to the wide range of colors and properties. The green variety is similar in color to Peridot gems. Cyprine, the blue variety of Vesuvianite, is colored by the addition of copper to its chemistry and is also refered to as Cupreous Idocrase or Cupreous Vesuvianite.
There are many sources of Vesuvianite such as Asbestos, Quebec, Canada; California, Colorado and the New England region of USA; Mt. Vesuvius, Italy; Ural Mountains, Russia, Switzerland, Tanzania and Kenya. However, there are only a few sources of gem quality crystals. A small amount of gemmy material has come from Asbestos, Quebec, Canada. Recent finds in Tanzania and Kenya have brought some very nicely colored gems to the market. One source of material is from California, USA and has been nick-named Californite or California Jade. This bright green opaque to translucent material comes from near Happy Jack mine, Siskiyou County and near Pulga, Butte County, California.
| Category: | Sorosilicate |
| Chemical Formula: | Ca19Al4Fe(Al,Mg,Fe)8Si18O7 |
| Calcium Aluminum Iron Silicate | |
| Molecular Weight: | 1,422.09 gm |
| Composition: | Calcium | 28.18 % | Ca | 39.43 % | CaO |
| Magnesium | 3.42 % | Mg | 5.67 % | MgO | |
| Aluminum | 7.59 % | Al | 14.34 % | Al2O3 | |
| Silicon | 17.77 % | Si | 38.03 % | SiO2 | |
| Hydrogen | 0.28 % | H | 2.53 % | H2O | |
| Oxygen | 42.75 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Tetragonal – Dipyramidal |
| Crystal Habit: | Crystals commonly as short pyramidal to long prismatic crystals, to 15 cm, morphologically complex, with up to 30 forms reported on one crystal; columnar, granular, massive. Californite is found in massive form, not as crystals. |
| Twinning: | Twinned domains observed at a very fine scale. |
| Cleavage: | Indistinct on {110}, {100} and {001] |
| Fracture: | Irregular/Uneven, Sub-conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.0 – 7.0 |
| Density: | 3.32 – 3.47 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Green, Brown, Colorless to White, Blue (Cyprine), Violet, Bluish green, Pink, Red, Black, commonly zoned; in transmitted light, Colorless to light Yellow, Green, Brown |
| Transparency: | Transparent, Translucent |
| Luster: | Vitreous, Resinous |
| Refractive Index: | 1.698 – 1.742 Uniaxial (+/-) |
| Birefringence: | 0.0040 – 0.0060 |
| Dispersion: | Strong; 0.019 – 0.025 |
| Pleochroism: | Weak; O = colorless to yellowish, E = yellowish, greenish, brownish |
