Source : Webster's Revised Unabridged Dictionary (1913)

Chalcedony \Chal*ced"o*ny\ (k[a^]l*s[e^]d"[-o]*n[y^] or
   k[a^]l"s[-e]*d[-o]*n[y^]; 277), n.; pl. {Chalcedonies}
   (-n[i^]z). [ L. chalcedonius, fr. Gr. CHalkhdw`n Chalcedon, a
   town in Asia Minor, opposite to Byzantium: cf. calc['e]doine,
   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}.]

   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.

Source : WordNet®

calcedony
     n : a milky or grayish translucent to transparent quartz [syn: {chalcedony}]