Sardonyx shell--not to be confused with the striped variety of Chalcedony, which is also known as sardonyx--is actually the shell of the giant sea snail, Cassis madagascariensis, otherwise known as the emperor or queen helmet shell.
Cassis madagascariensis is native to Bermuda, Venezuela, the West Indies and certain parts of the United States, including North Carolina. It is rare, however, so sardonyx shell is expensive.
Appearance
Sardonyx shells are roughly 12 inches in height, or length. They are dark, chestnut brown on the inside but perfectly white on the outside. The resemblance of sardonyx shell to marble adds to its value.
Uses
The coloration and thickness of sardonyx shell make it ideal for carving relief medallions, brooches and rings, known as cameos. Indeed, some of the most valuable cameos in the world are carved from sardonyx shell. A typical antique sardonyx cameo brooch could easily cost you as much as $2,500.
Tags: Cassis madagascariensis, ,