Brownish-black Grossular Garnet (from Tanzania of Africa)

Description: Matrix specimen of sparkling, lustrous brownish-black Grossular crystals.

Locality: Tanzania

Dimensions:  39x29x28 mm

Weight: 53.6 gram

***

Grossular Garnet

Grossular is member of the Garnet group, and is its most varicolored form, occurring in almost all colors except for blue. Grossular is often dark in color, but it also forms the lightest colored forms of Garnet, and can even be white or colorless. Although not as famous as Almandine and Pyrope, Grossular has some important gem varieties. These include the rare emerald-green Tsavorite and the orange to orange-brown Hessonite.

Grossular forms a solid solution series with Andradite, and can be virtually indistinguishable from it in localities where they both occur together. In some localities such as Mali, a distinction between these two Garnets is sometimes too complex, and a specimen may just be called "Andradite/Grossular since its full identification is lacking. Grossular is named for its color resemblance to gooseberries, which are scientifically known as ribes grossularium.

Chemical Formula Ca3Al2Si3O12

Composition Calcium aluminum silicate, often with some iron, manganese, or chromium replacing some aluminum

Color Brown, orange, green, yellow-green, and gray. Less often pink, red, and yellow. Rarely white, and colorless. Some massive specimens may be multicolored white, light green, and pink.

Hardness 6.5 - 7.5

Crystal System Isometric

Transparency Transparent to nearly opaque

Luster Vitreous