Onyx, the seventh anniversary stone, is the name given to finely textured chalcedony, colored black. Sometimes onyx has white banding or ribbons in the black of the stone. The stone was very popular in ancient Greece and Rome. Its name, in fact, comes from the Greek word "onux", meaning fingernail. As it is with most gemstones, onyx too has legends attached to it. One such legend relates that Cupid cut the fingernails of the Goddess Venus. He used an arrowhead and did the cutting while she slept. The fingernail clippings were “collected” by the fates, who not wanting any part of the Goddess disposed of irrelevantly, turned them into stone. Albeit that black isn't really the color fingernails, in ancient Greece, the colors of chalcedony went from white to dark brown and black. Later on the Romans reclassified the stone and considered only black and dark brown to be onyx.

There are other shades of onyx, specifically those stones that are reddish brown and white. These are called sardonyx. In ancient Rome, the unique property of sardonyx, which did not stick to wax, was very valuable because it was used to fashion royal seals. Roman General Publius Cornelius Scipio was known for wearing lots of sardonyx.

Black onyx’s fine texture makes it a perfect medium for carving. In history, it was often used as a “backdrop” for carved rock crystal, or, in Art Deco, “against” rubies. If the onyx layers are even, it can be carved into cameos. Today, it continues to be popular in use with marcasite jewelry.