Sardonyx is a variety of chalcedony, with is a crystalline quartz. Also known as sardian onyx it is a blend of sard and onyx. Ancient texts noted that the only truly valuable colors of Sardonyx were black, red and white-the three ancient colors of the Triple Goddess.
The name of this stone is of course the combination of the names of two other healing stones, onyx and sard. The healing and protective properties of Sardonyx have been exhaulted since antiquity.