Shell is probably the most popular material since the late 18th Century because less expensive than other precious material like agate or coral. But we know shell cameos from Renaissance or even from Roman Empire. Here a list of the most common shell used for cameos. Below are several samplees of shell cameos. Cassis Madascariensis (Sardonix) Cassis Cornuta (Carnelian) Strombus Giga (Pink Shell) Cypraea Tigris (Tigrina) Cassis Madagascariensis: ca 12 inches. Chestnut brown at bottom, and perfectly white on the surface for engraving. Cassis Rufa: ca 6 inches. Has an interior reddish layer; the exterior for engraving is pale flesh-coloured. Strombus Gigas: ca 11 inches. Its white and pink layers are not always perfectly distinct from each other; also used for necklaces and buttons, fished in the Bahamas. Cypraea Tigris: ca 2-4 inches. Has seven different layers of colour. In order: tiger brown on the surface. Then white-yellonwish, grey-blue, two tones of purple and finally a slightly blueish white. Fished in Indo-Pacific.