Mineralogy is the science that involves the study of minerals. A scientist who studies in this field is known as a mineralogist.
Prixus, a science division Starfleet officer serving aboard the USS Enterprise-D specialized in the fields of mineralogy and metallurgy.
In 2365, as mineralogy was one of many areas of focus for acting ensign Wesley Crusher's mission to a planet in the Selcundi Drema system, he chose Prixus to be on the away team. (TNG: "Pen Pals")