chalcedony \chalced"ony\ ka^lse^d"-ony^ or
   ka^l"s-ed-ony^; 277, n.; pl. chalcedonies
   -ni^z.  l. chalcedonius, fr. gr. chalkhdw`n chalcedon, a
   town in asia minor, opposite to byzantium: cf. calc'edoine,
   oe. calcidoine, casidoyne. cf. cassidony. min.
   a cryptocrystalline, translucent variety of quartz, having
   usually a whitish color, and a luster nearly like wax.
   written also calcedony.
   1913 webster

   note: 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.
         1913 webster
see also:
chalcedonies cassidony calcedony agate onyx chrysoprase 
carnelian sard