cameo

A small-scale, low relief carved in a stratified or banded material, usually a gemstone such as onyx or sardonyx, but also in shell, clay or glass. The cameo technique results in a background of one color and an image in relief of another color.

UntitledThe Gemma Augustea, a cameo carved from a piece of onyx. Early 1st century CE. Kunsthistorisches Museum, Vienna.