Sardonyx is an orange version of onyx. Sardonyx is a variety of agate with reddish-brown and white bands with a hardness of 6.5. Sard is the brownish-red variety of chalcedony. Sardonyx has straight bands of white, together with bands of brownish red sard thus, the name sardonyx. Sard takes its name from the Greek “Sardis,” the capital of ancient Lydia. Until the middle Ages sard shared the name “sardion” with carnelian.
Ancient Egyptians wore sardonyx as a talisman. Romans also believed that it gave courage when going into war and in Renaissance Europe, wearing a sardonyx stone was believed to bestow eloquence on speakers.
Sardonyx is found in India where it has been mined since ancient times. It still remains a major source. It is also found in the Ural Mountains of central Russia, and in the United States in Tampa Bay, Florida, and El Paso County, Texas. Major deposits of sard are found in Ratnapura, Sri Lanka. Other sources are India, Brazil, and Uruguay.
Sardonyx is an alternative birthstone for the month of August.