Sardonyx is a gemstone made of layered sard (reddish-brown chalcedony) and onyx (banded chalcedony), giving it its distinctive striped appearance. Since both sard and onyx are varieties of chalcedony, which is a type of agate, sardonyx is considered a form of agate. Historically valued for jewelry and carvings, it is also believed in metaphysical traditions to bring strength, courage, and protection.
