pe·trol·o·gy /pəˈtrɑləʤi, pɛ-/
  巖石學
  Pe·trol·o·gy n.
  1. The department of science which is concerned with the mineralogical and chemical composition of rocks, and with their classification: lithology.
  2. A treatise on petrology.
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  petrology
       n : the branch of geology that studies rocks: their origin and
           formation and composition