What Are Rocks?

Rocks are combinations of one or more minerals that we find in nature.

For example:

• Limestone is composed of only one mineral – calcite
• Basalt is commonly composed of three minerals – feldspar, pyroxene, and olivine
• Granite is commonly composed of five minerals – two kinds of feldspar, mica, amphibole, and quartz

Just like minerals, there are many different kinds of rocks. Geologists group rocks into three different categories; igneous, sedimentary, and metamorphic.

• Igneous rocks form from magma or lava
• Sedimentary rocks form from pieces of other rocks or are formed by minerals being precipitated from water
• Metamorphic rocks form by recrystallizing the minerals in a rock under high pressures or temperatures