Spinel

Spinel is a gemstone that comes in a variety of colors. Pure Spinel is colorless, but impurities are responsible for the wide range of colors. The most valuable and desirable Spinel color is a deep blood red, though blue, yellow, orange, pink, and purple colors also make fine gemstones.

Color Various; Red and Pink to Blue to Mauve, Dark Green, Brown, Black
Mohs scale hardness 8.0
Specific gravity 3.58 - 4.06
Refractive index 1.712 - 1.717