Mineralogy
Mineralogists (people who study minerals) study minerals in rocks with hand lenses (a magnifying glass), and in thin section (thin slices of rock) with microscopes. They record things about the minerals like how big they are, what shape they are, what color they are, and if the mineral changes colors when you turn it. Mineralogists also record what color minerals turn in a special light. These details can help mineralogists figure out what minerals they are looking at.