Source : Webster's Revised Unabridged Dictionary (1913)

Mineralogy \Min`er*al"o*gy\, n.; pl. {Mineralogies}. [Mineral +
   -logy: cf. F. min['e]ralogie.]
   1. The science which treats of minerals, and teaches how to
      describe, distinguish, and classify them.

   2. A treatise or book on this science.

Source : WordNet®

mineralogy
     n : the branch of geology that studies minerals: their structure
         and properties and the ways of distinguishing them