Spinel is a mineral composed of magnesium aluminate. It crystallizes in the isometric system, usually in hexahedral crystals with a vitreous luster. Various amounts of impurities, such as iron, manganese, and chromium impart different colors to the mineral, including red, lavender, blue, green, brown, or black.

The clear red variety, which is almost pure magnesium aluminate, is known as ruby spinal or balas ruby. Spinel containing iron is dark in color, and is known as pleonaste or ceylonite. Spinel containing chromium is yellowish to greenish brown and is known as picotite. The hardness of the mineral is 8, and the specific gravity ranges from 3.5 to 4.1.

Transparent and finely colored specimens are used as gemstones. Most spinel gemstones are the red ruby spinel variety. Ruby spinels are found in the sands of Ceylon and Madagascar. In the United States ordinary spinel occurs in New York and New Jersey.

Magic & Myth

Spinel was recognized as a mineral only 150 years ago; prior to this it was classified as a ruby and shared the ruby's reputed medicinal and prophetic power. It was also used as a remedy for hemorrhages.