The Probert Encyclopaedia of Rocks & Minerals

SPINEL

Spinel is a common metamorphic mineral occurring imbedded in crystalline limestone, gneisses, and serpentine. Spinel occurs as a common accessory mineral in many dark igneous rocks. When transparent and finely coloured it is often confused for ruby and is used as a gem stone. An oxide of magnesium and aluminium it has the formulae MgAl2O4 and a relative hardness of 8.
Research Spinel