The Collaborative International Dictionary of English v.0.48:

Ammite \Am"mite\ ([a^]m"m[imac]t), n. [Gr. 'ammi`ths, 'ammi`tis,
   sandstone, fr. 'a`mmos or "a`mmos sand.] (Geol.)
   O["o]lite or roestone; -- written also hammite. [Obs.]
   [1913 Webster]