Question

how do rocks differ from minerals

Answer 1

Well, rocks are composed of minerals while minerals are made of one or more elements.

Answer 2

Rocks are made up of minerals. Sometimes the rocks are quite pure samples of those minerals. For instance, chalk is a mineral (calcite), and a rock (limestone) and can be found in great seams - the white cliffs of Dover are an example - though where I live, the chalk deposits have great chunks of flint (quartz = mineral) in them. When a mineral is present in sufficiently pure form that it is the bulk of the material, we tend to call it a rock, and use a different name.