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 ...

Experts say that this previously overlooked gemstone is rocketing in desirability ... part of the British Crown Jewels, is in fact a spinel. In 2015, the auction house Bonhams sold the 50.13 ...

Portuguese gem traders traveled across the empire from ... Sadly, the bracelet doesn’t exist any more. Image A red spinel engraved with the names of six rulers by Sa’ida Gilani, an Iranian ...