Jewelry auctions are in full swing for the holiday, and, in the spirit of the season, red-toned stones topped the lots for ...

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 ...

Image A red spinel engraved with the names of six rulers ... It was set with emeralds, diamonds, rubies and pearls, some from the emperor’s personal collection. The contemporary sources mention ...