Silicate of calcium and aluminium, belonging to the garnet group. The name grossular is due to the fact that some of these crystals resemble gooseberries, the Latin name for which is grossularia.
Crystal system Cubic.
Appearance Grossular also has the typical crystal form of garnets, occurring in isolated crystals which are often complete, in the shape of a rhombic dodecahedron, sometimes combined with a trapezohedron. They vary from transparent to semiopaque. The typical color is light (gooseberry) yellowish green; but they can be a strong to bluish green, honey yellow or pinkish yellow, or even perfectly colorless. When transparent, the crystals have good luster. Like other garnets, they have no cleavage. The greenish to yellowish varieties are used as gems.
Physical properties The hardness is 6.5-7.5 or a little more. The density is somewhat variable: from 3.58 to 3.69 g/cm“. The refractive index is about 1.74.
Occurrence Grossular is not a rare mineral. The types used as gems mainly come from the gem gravels of SriLanka (honey yellow variety); and the United States, Canada, Mexico, Madagascar, Kenya, and Tanzania (green variety).