A geologist who is also a mineralogist would generally study:

A) minerals, like quartz and halite
B) vitamins and minerals, like potassium and calcium
C) coal mining techniques
D) mine collapses

Mineralogist

A scientist who specializes in the study of minerals, their composition, structure, properties, and the processes that lead to their formation.

Minerals

Naturally occurring, inorganic solids with a definite chemical composition and a crystalline structure, found in rocks and the Earth's crust.

Quartz

A hard, crystalline mineral composed of silicon and oxygen atoms, widely used in jewelry and electronics.