The Collaborative International Dictionary of English v.0.48:

Sard \Sard\, n. [L. sarda, Gr. ?, or ? (sc. ?), i.e., Sardian
   stone, fr. ? Sardian, ? Sardes, the capital of Lydia: cf. F.
   sarde. Cf. Sardius.] (Min.)
   A variety of carnelian, of a rich reddish yellow or brownish
   red color. See the Note under Chalcedony.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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.]
   [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]

WordNet (r) 3.0 (2006):

sard
    n 1: a deep orange-red variety of chalcedony [syn: sard,
         sardine, sardius]