The study of rocks is known as-

Petrology - the scientific study of how rocks are made and what they are made of.
Sinology - the study of Chinese language, history, customs and politics
Geology - the scientific study of the physical structure of the earth, including the origin and history of the rocks and soil of which the earth is made.
Numismatics - the study of coins and medals.
[source: oxfordlearnersdictionaries.com]