li·thol·o·gy \lə̇ˈthäləjē, -ji\noun (-es) Etymology:lith- + -logy 1.: the study of rocks 2.: the character of a rock formation or of the rock found in a geological area or stratum expressed in terms of its structure, mineral composition, color, and texture < a relation between the fossil content of a stratum and its lithology — F.J.Pettijohn >