The Collaborative International Dictionary of English v.0.48:

Nepheline \Neph"e*line\ (n[e^]f"[-e]*l[i^]n), Nephelite
\Neph"e*lite\ (n[e^]f"[-e]*l[imac]t), n. [Gr. nefe`lh cloud: cf.
   F. n['e]ph['e]line. Cf. Nebula.] (Min.)
   A mineral occuring at Vesuvius, in glassy hexagonal crystals;
   also elsewhere, in grayish or greenish masses having a greasy
   luster, as the variety elaeolite. It is a silicate of
   aluminia, soda, and potash.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nepheline
    n 1: a whitish mineral consisting of sodium aluminum silicate or
         potassium aluminum silicate in crystalline form; used in
         the manufacture of ceramics and enamels [syn: nepheline,
         nephelite]