Spinel

Spinel is both an individual mineral as well as a group of metal-oxide minerals. The minerals in the groupe include gahnite, franklinite, and chromite. The red variety is called Ruby spinel. It can be glassy, hard octahedra, as grains, or masses. It is common to find in crystalline limestone, gneisses, and serpentine.

Species: spinel ♦ Chemistry: MgAl2O4 ♦ Color: red, pink, blue, lavender/violet, dark green, brown, black, colorless ♦ Cleavage: none ♦ Fracture: irregular ♦ Transparency: transparent to opaque ♦ Luster: vitreous ♦ Crystal System: cubic ♦ Moh's Hardness: 7.5-8 ♦ Localities: Burmal, Canada, Italy, Germany, Madagascar, Tajikistan, USA.