The Collaborative International Dictionary of English v.0.48:

Cornelian \Cor*nel"ian\ (k?r-n?lyan), n. [F. cornaline, OF.
   corneline, fr. L. cornu horn. So called from its horny
   appearance when broken. See Horn, and cf. Carnelian.]
   (Min.)
   Same as Carnelian.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cornelian
    n 1: a translucent red or orange variety of chalcedony [syn:
         carnelian, cornelian]