The word Cameo literally means figure carved in low relief. Among the shells used in the work of the most valued Cameos are the "cassis madagascariensis" and "cassis rufa", respectively called sardonic and carnelian because they are of the same color of these stones.
The sardonic is from the Caribbean and the Bahamas, the carnelian is instead of African origin.
The shells are cut and carved by hand. Working on two layers of different colors you can represent anything you want.
Cameo can be achieved by any material. In fact, we have those in lava, bone, shell pink, pearl, coral, turquoise etc.