Spinel

Spinel (pronounced Spin-el) known for is vibrant royal colors was a very popular gem in the Renaissance era. It comes in a few colors such as Red, Blue, Black, Gray, and Pink. It belongs to the cubic crystal system but forms octahedron crystals, imagine taking 2 pyramids and putting the bottoms together to make this sort of 3 dimensional diamond shape. Its formed when magnesium rich limestone is subjected to intense heat and pressure allowing the magnesium and aluminum to combine with oxygen to form Spinel crystals

Hardness: 8
Composition: MgAl₂O₄