A mineralogist is a scientist who studies minerals — the natural solid pieces that make up rocks, such as quartz, salt crystals, or gold in the rock. They ask what a mineral is made of, how it formed, and how to tell two look-alike minerals apart. The ending -logist names a person who studies a field, the way a biologist studies living things. The field itself is mineralogy, not mineralogist. You will meet the word in universities and museums, not in the market. Though actually, people sometimes mix this person up with a geologist. A geologist looks at the Earth in a wider way — rocks, mountains, time — while a mineralogist zooms in on the mineral pieces.