Part of the EASP Geology Walk Granite is an intrusive igneous rock formed deep in the earth. When magma cools, minerals within it form crystalline grains. On the earth’s surface lava cools quickly to form small crystalline grains (and therefore rocks such as rhyolite), but beneath the surface of the earth, magma takes a much longer time to cool. This allows the minerals to develop into much larger grains. Rocks with these larger grains are said to have a coarse-grained texture. Granite is composed mainly of feldspar and quartz. Department of Earth, Atmospheric, and Planetary Sciences
