Today the most popular shells for carving are the bull mouth carnelian shell, Cassis rufa, from the East African coast; this has white and orange or white and brownish-orange layers.
The most highly prized shell for carving is the emperor helmet shell, Cassis madagascariensis. This shell has white and dark brown layers and is known as sardonyx shell, and looks similar to the layered agate known as sardonyx. The world centre for cameo carving in shell is Torre del Greco, Italy. The shells are first marked with a series of ovals in a process called signing, then cut into oval blanks for the cameo carver. The actual cameo is mainly cut with a metal scraping tool called a bulino, an invention of Jewish artisan Antonio Cimeniello. A number of metal gravers are used: flat-faced, round and three-cornered. To speed production, grinding wheels are used to quickly remove excess material. When the details are completed, the shell is then soaked in olive oil, cleaned with soap and water and selectively polished with a hand brush.
Location - Italy