Concept:
Different branches of earth science study different materials and processes.
Step 1: Geology is the broad study of the earth, rocks, and earth processes.
Step 2: Petrology is the study of rocks.
Step 3: Metallurgy is the science of extraction and processing of metals.
Step 4: Mineralogy is the branch that deals with the study of minerals, their composition, structure, properties, and classification.
Therefore, the study of minerals is called:
\[
\boxed{\text{Mineralogy}}
\]