Formula: MgAl2O4

Colour: Black, blue, red, violet , green, brown, pink

Lustre: Vitreous

Hardness: 7½ – 8

Specific Gravity: 3.6 – 4.1

Crystal System: Isometric

Member of: Spinel Subgroup > Oxyspinel Group > Spinel Supergroup; Spinel-Hercynite Series, Gahnite-Spinel Series, and the Magnesiochromite-Spinel Series.

Name: Named in 1779 by Jean Demeste from Latin “spinella”, little thorn, alluding to its sharp octahedral crystals. Confused with carbuncle = ruby in former times.

Intensely coloured varieties due to the incorporation of various impurity elements. A few spinels from Sri Lanka can show an alexandrite colour change effect.