Spinel, MgAl 2 O 4 (download cif), is a rare gemstone that was used to imitate rubies. The structure has face-centered cubic symmetry, and is a little heavy to understand. The general formula is AB 2 ...

Spinel comes in a wide range of colors, including red, pink, orange, purple, blue and green. As a result, the symbolism of this gemstone depends on its color. For instance, red spinel is ...