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 ...

In 2016, jeweler Olivia Young of Ouroboros sold a red spinel ring for £6,000 ($7,700 ... gemstone is rocketing in desirability and value, as collectors look beyond the so-called “Big Four ...