The Collaborative International Dictionary of English v.0.48:

Augite \Au"gite\ ([add]"j[imac]t), n. [L. augites, Gr.
   a'ygi`ths, fr. a'ygh` brightness: cf. F. augite.]
   A variety of pyroxene, usually of a black or dark green
   color, occurring in igneous rocks, such as basalt; -- also
   used instead of the general term pyroxene.
   [1913 Webster]

WordNet (r) 3.0 (2006):

augite
    n 1: dark-green to black glassy mineral of the pyroxene group
         containing large amounts of aluminum and iron and magnesium