NOUN (1)

1. a white or greenish aluminum silicate mineral (resembles talc);

The Collaborative International Dictionary of English v.0.48:

Pyrophyllite \Py*roph"yl*lite\, n. [Pyro- + Gr. ? leaf.] (Min.)
   A mineral, usually of a white or greenish color and pearly
   luster, consisting chiefly of the hydrous silicate of
   alumina.
   [1913 Webster]