Grossular dodecahedral crystal. Grossular is a calcium-aluminium mineral species (Ca3.Al2.(SiO4)3), part of the garnet group of minerals. It most often occurs in contact metamorphic rocks. Of all garnets it can have the lightest colours, and can even be white or colourless, but most often occurs in colours ranging from light to dark green, yellow to reddish-brown, and translucent to opaque pink, but never blue. Its crystal system is cubic, and crystals can form as a dodecahedron. This crystal is well-developed and exceptionally large. Found at Lake Jaco in Chihuahua, Mexico, it is 11 centimetres across.