An ornamental stone that is a variety of agate, a kind of chalcedony. It is an onyx composed of two or more layers of milk-white chalcedony and transparent red sard. However, the contrasting layer is sometimes golden or brown. The red layer showing through the white one appeared much like the color of a fingernail to the Greeks, which was probably why they applied to it the Greek word oʹnyx (meaning “fingernail”). Sardonyx is found in various places, including Palestine and Arabia.