Grossular (Garnet)
Grossular, also known as Grossularite, is a known member for the Garnet band of minerals that includes Almandine, Andradite, Grossular, Pyrope, Spessartine and Uvarovite. The title Grossular is based on the title that is botanical the gooseberry, Ribes Grossularium, in reference towards the green variety of Garnet that was originally found in the Vilyui River Basin, Eastern-Siberian Region, Russia. Other shades of Grossular include cinnamon-orange to brown, red, and yellow.
The more variety that is common of is called Hessonite through the Greek word “hesson” meaning “inferior”, because of its substandard hardness to many other kinds of Garnet. Hessonite Garnets range in color from cinnamon-brown to orange and have been called the “Cinnamon Garnet” as a result of its color. The color arrives to the addition of iron to its chemical formula. Gem quality Hessonite is situated in Sri Lanka, Tanzania, Brazil and California, United States Of America.
Another variety of Grossular is the very highly wanted after deep Grossular that is green known Tsavorite. It was discovered in 1971 by British treasure gemologist and prospector Campbell R. Bridges. The name Tsavorite was proposed in 1974 by Tiffany and Company president Sir Henry Platt in honor associated with the Tsavo National Park in Kenya were Bridges discovered it. Tsavorite’s deep color that is green due to trace amounts of vanadium or chromium.
Rosolite, also referred to as Rose Garnet or Xalostocite, is really a variety that is rose-pink of from Sierra de la Cruz, Mun. de Sierra Mojada, Coahuila, Mexico.
Viluite is another variety of Grossular that is not really well understand. It will always be olive green though sometimes reddish or brownish and comes through the Wilui River Basin area of Eastern Siberia, Russia.
Hessonite, Tsavorite, Rosolite and Viluite are kinds of Grossular and generally are perhaps not recognized as distinct mineral species. Grossular in addition has been given nicknames such as African Jade and Transvaal Jade.
Grossular Garnets are found at many localities, even for fine crystals and gem material. In Russia, near Chernyshevsk, at the confluence regarding the Vilyui and Akhtaragda streams, Yakutia. Within the Ala Valley, Piedmont, Italy. From the Zillertal, Tirol, Austria. At Ocna de Fier, Romania. In the Jeffrey mine, Asbestos, Quebec, Canada. In the USA, at Standish, Cumberland County, Maine, and at the Belvidere Mountain quarries, Lowell, Orleans County, Vermont. The Old Cosumnes copper mine, El Dorado County, San Carlos mine, Mazourka Canyon, Inyo number, Inyo County, and Santa Rosa, Sonoma County; on Vesper Peak, Sultan basin, Snohomish County, Washington in California, from Crestmore, Riverside County. In Mexico, large crystals from Xalostoc and Morelos, Chihuahua, and from the Sierra de la Cruces, near Lake Jaco, Coahuila. Gems from the Merelani Hills, southeast of Arusha, Tanzania. In the Taita Hills, near Voi, Kenya.
| Chemical Formula: | Ca3Al2(SiO4)3 |
| Calcium Aluminum Silicate | |
| Molecular Weight: | 450.45 gm |
| Composition: | Calcium | 26.69 % | Ca | 37.35 % | CaO |
| Aluminum | 11.98 % | Al | 22.64 % | Al2O3 | |
| Silicon | 18.71 % | Si | 40.02 % | SiO2 | |
| Oxygen | 42.62 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | Commonly in dodecahedra or trapezohedra, up to 15 cm, with striated faces. Also granular, compact, and massive. |
| Twinning: | None observed |
| Cleavage: | None observed. Parting rarely observed on {110}. |
| Fracture: | Irregular/Uneven, Sub-Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.5 – 7.0 |
| Density: | 3.594 (g/cm3) |
| Luminescence: | Almost always non-fluorescent; may be a weak golden yellow under LW & SW UV. |
| Radioactivity: | Not Radioactive |
| Color: | Yellow-Green, pale to dark Green; golden Yellow, Pink, Red, Orange, Brownish Red, Yellowish Brown; Colorless, White, Gray, Black; may be sectored: Colorless in thin section. |
| Transparency: | Transparent to Opaque |
| Luster: | Vitreous, Sub-Vitreous, Resinous |
| Refractive Index: | 1.731 – 1.754 Isotropic. RI increases with increasing iron contents (usually Fe3+). |
| Birefringence: | 0.000 (Isotropic); may have weak strain birefringence of 0.0 – 0.005 |
| Dispersion: | Strong |
| Pleochroism: | None |
