1. Min. Chalcedony in parallel layers of different shades of color. It is used for making cameos, the figure being cut in one layer with the next as a ground.
Onyx marble, Mexican onyx, a banded variety of marble or calcium carbonate resembling onyx. It is obtained from Mexico in various colors ranging from white to deep black.
n : a hard compact kind of calcite [syn: alabaster, oriental
alabaster, onyx marble]