Sardonyx (sar-DON-ix or SAR-duh-nix) is a variety of onyx where some bands are sard (carnelian), meaning they are orange or red-orange. The remaining bands can be white, black, or both. Because it is a type of onyx, it is also a type of chalcedony. Like onyx, the planar bands in sardonyx make it an appealing medium for relief carvings.
Because sardonyx is a type of chalcedony, putting it in the quartz family, it has a Mohs hardness of 6.5 to 7 and a trigonal crystal structure.
It is the alternate birthstone for August (the main one being peridot).
Location: Sardonyx has been mined in India for thousands of years, and arguably produces the finest quality specimens. Other major sources include Brazil, Germany, Russia, the Czech Republic (Czechoslovakia), and the United States.
Properties: Sardonyx combines the properties of sard (carnelian) and onyx, so reading the entries for those stones will help clarify the nature of sardonyx. This stone also has some properties of its own to add; that is, it helps bring harmony to marriage or common-law relationships, attract good fortune and friendships, develop self-control, and instill courage.
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