Mostly descriptive rock and mineral terminology
First off the most important: mineral is a naturally occurring solid substance formed by natural processes, with a specific chemical composition.
Rock is a naturally occurring solid substance of one (but usually at least two) or more minerals. Gem or gemstone are terms used loosely to describe the best minerals and rocks. And Stone is really not a scientific term but is used often in the commercial trade.
The fields of study and the people who study them include:
- Gemology/Gemologist the study of gemstones.
- Geology/Geologist the study of substance that makes up earth.
- Mineralogy/Mineralogist the study of minerals.
- Paleontology/Paleontologist the study of prehistoric life and fossils.
- Lapidary means "concerned with stone" and is used to encompass the entire field as well as the art of cutting stones and the person who does the cutting.