Mineralogy was 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, considered to be "the best" within the discipline aboard the ship.
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")