Rocks are aggregates of minerals.
These three groups are distinguished by the way the rock forms. Igneous rocks may form from magma that cools after being erupted onto earth's surface, or the magma might never reach the surface, but cool underground instead. The texture of igneous rocks reflect their cooling history, and their mineral composition depends on the chemical composition of the magma from which they formed. Magma composition is partly related to the chemical composition of the original rock that melted, certain igneous rock types are associated with certain plate tectonic settings. In this lab we will learn how to describe igneous rocks, give them names, and a little about the plate tectonic settings in which the different igneous rock types typically form.