The Collaborative International Dictionary of English v.0.48:

Phonolite \Pho"no*lite\, n. [Phono- + -lite: cf. F. phonolithe.]
   (Min.)
   A compact, feldspathic, igneous rock containing nephelite,
   ha["u]ynite, etc. Thin slabs give a ringing sound when
   struck; -- called also clinkstone.
   [1913 Webster]