lithology
noun
li·thol·o·gy li-ˈthä-lə-jē 
plural lithologies
1
: the study of rocks
2
: the character of a rock formation
also : a rock formation having a particular set of characteristics
lithologic
ˌli-thə-ˈlä-jik
adjective or lithological
ˌli-thə-ˈlä-ji-kəl
lithologically
ˌli-thə-ˈlä-ji-k(ə-)lē
adverb 
Word History
Etymology
litho- + -logy, probably after New Latin lithologia or French lithologie
First Known Use
1716, in the meaning defined at sense 1