Spinel is found in a wide range of colours due to the presence of various impurities, and is transparent to almost spinel by chromium and iron is the most popular, although for many years it was thought to be a variety of ruby. The orange- yellow or orange-red variety is called rubicelle(a diminutive of the French word for ruby) Blue spinel is coloured by iron, and less commonly by cobalt. Occasionally, inclusions of crystals such as magnetite or apatite may occur, and some Sri Lankan spinels may include con crystals surrounded by brown haloes. Star stones are rare, but when cut en cabochon may show 4-rayed or 6-rayed stars.
|Composition||Magnesium Aluminium Oxide|