The Collaborative International Dictionary of English v.0.48:

Ceria \Ce"ri*a\ (s[=e]"r[i^]*[.a]), n. (Chem.)
   Cerium oxide, CeO2, a white infusible substance
   constituting about one per cent of the material of the common
   incandescent mantle.
   [Webster 1913 Suppl.]