How to Buy Sardonyx
Sardonyx makes a great gift for people born in August who want something a little different than the traditional peridot birthstone. Readily available and relatively inexpensive, sardonyx makes an affordable addition to anyone’s collection.
The most attractive sardonyx shows high contrast between reddish layers of sard stone and white bands of onyx. It may be translucent or opaque, seldom showing flaws or fractures.
Sardonyx is widely available and moderately priced in sizes up to 10 carats. The most common cut is cabochon, though it is popularly carved into cameos, intaglios, inlays and broaches to emphasize the contrast between layers.
Artificial and imitation sardonyx has been produced from common chalcedony and plain agate as far back as Roman times, according to writings from first-century naturalist, Pliny. Some gems are also stained with iron oxide pigment or treated with nitric acid to enhance color.
These enhancements make stones less valuable than natural sardonyx, so watch for imitations when buying these gems.