Spinel, MgAl2O4, is a very attractive and historically important gemstone. In fact, many rubies of crown jewel collections were actually red spinels. Although the most common spinel color is red, it also comes in green, blue, purple, brown and black. Spinel is very hard, being 7.5 to 8.0 on the mohs scale. The refractive index is 1.71 to 1.76 with an isometric crystal system. Important sources are Burma, Sri Lanka, Afghanistan and Brazil. Keep in mind that we can mount any of these loose spinel gemstones in jewelry of your choice. Our finished spinel jewelry can be viewed here.