A mineral occuring in octahedrons of great hardness and various colors, as red, green, blue, brown, and black, the red variety being the gem spinel ruby. It consist essentially of alumina and magnesia, but commonly contains iron and sometimes also chromium.
A hard, glassy mineral occurring in many various attractive colors: red, rose, orange, brown, pink, yellow, blue, violet, purple, mauve, green, and black. Completely colorless (white) spinel is rare. Some years ago, synthetic white spinel was used in costume jewelry as a diamond substitute. Although natural spinel is quite hard, the synthetic spinels were not very hard, so spinel developed an undeserved reputation as a low-quality stone.
Spinel is the classification of a large group of related minerals that has a small group of gemstone quality stones. Spinel exhibits a wide range of colors including red, pink, orange, yellow, brown, blue, violet, purple, green and black. On Mohsâ€™ scale of hardness, spinel is 8. Sources include Burma (Myanmar), Cambodia, Sri Lanka, Afghanistan, Australia, Brazil, Madagascar, Nepal, Nigeria, Tadzhikistan, Tanzania, Thailand and the United States (New Jersey). (See Spinel Facts.) (Note: Sources listed in order of primary and secondary deposits.)