Chalcedony
Chalcedony (kal*sed"o*ny or kal"se*do*ny; 277) , noun
[ Latin chalcedonius, from Greek CHalkhdw`n Chalcedon, a town in Asia Minor, opposite to Byzantium: compare calcédoine, Old English calcidoine, casidoyne. Compare Cassidony.]
(Mineralogy) A cryptocrystalline, translucent variety of quartz, having usually a whitish color, and a luster nearly like wax.
When chalcedony is variegated with with spots or figures, or arranged in differently colored layers, it is called agate; and if by reason of the thickness, color, and arrangement of the layers it is suitable for being carved into cameos, it is called onyx. Chrysoprase is green chalcedony; carnelian, a flesh red, and sard, a brownish red variety.