A rock is a solid material made of one or more minerals. The minerals the rock is made of help determine the properties of that rock. All of the rocks in the earth's crust can be grouped into three categories based on how they formed. Rocks are classified into three groups. The way a rock formed determines which group it is in. They may range in size from tiny pebbles to huge mountains. Rocks make up the earth’s crust. Many rocks are not solid -- such as magma, dirt, and clay. In general, the only people interested in rocks are geologists. Different mineral deposits can be found in related rock formations, providing use by estimating what minerals rock formations may contain.
Types of Rocks
- Interactive Rock Cycle Learn how to distinguish between types of rocks and discover how rocks change over time.