The Collaborative International Dictionary of English v.0.48:

Ampelite \Am"pe*lite\ ([a^]m"p[-e]*l[imac]t), n. [L. ampelitis,
   Gr. 'ampeli^tis, fr. 'a`mpelos vine.] (Min.)
   An earth abounding in pyrites, used by the ancients to kill
   insects, etc., on vines; -- applied by Brongniart to a
   carbonaceous alum schist.
   [1913 Webster]