Sardonyx is generally formed hydrothermally in the hollows of other rocks. Although found worldwide, major concentrations found in the eastern US are what is generally available in todays marketplace.
When used in jewelry, you may see it many times as a black and white or as an orange and white stripe pattern. It gets its name from basically being a composite of reddish brown Sard (Carnelian) and Onyx. While it is another ‘combination’ gem, it has its own unique healing qualities, but also contains the benefits of its makeup gems of Onyx, Carnelian and Chalcedony in varying degrees.