Spinel (/spɪˈnɛl, ˈspɪnəl/) is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4 in the cubic crystal system. The name comes from the Latin word spinella, a diminutive form of spine, in reference to its pointed crystals. Spinel crystallizes in the isometric system; common crystal forms are octahedra, usually twinned. It has no true cleavage, but shows an octahedral parting and a conchoidal fracture. Its hardness is 8, its specific gravity is 3.5–4.1...
