Grossular is the calcium aluminum garnet and forms in contact or regional metamorphic enviroments as does andradite the calcium iron garnet. It is believed that these garnets form from the metamorphism of impure siliceous limestones. Grossular has many color possibilities and is probably the most colorful of the garnets. The orange variety is the most common and specimens of orange grossular crusts are prized by many collectors. Green variety is called tsavorite and is occassionally cut as a gem.
Hessonite is a red variety of grossular and is also sometimes used as a gem.
Color is colorless, yellow, orange, green, red, grey and black. Luster is vitreous. Transparency crystals are transparent to translucent. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive and granular occurrences are also seen.