Crystal system: Cubic (crystals usually octahedra or dodecahedra)
Hardness: 8
Density: 3.5
Colour: Red when pure but can be colourless, yellow, green, or blue.
Streak: White.

Spinel occurs in magmatic and contact metamorphic rocks. Occurrence is rare. Primary use is as gemstones.

The picture shows lovely blue terminated spinel crystals from Aliabad, Hunza Valley, Pakistan.