Granite is an intrusive igneous rock that forms underground in volcanic areas. During formation the magma cools slowly, resulting in a coarse-grained texture with crystal sizes ranging from 1 mm – 10 mm in diameter. Being non-vesicular, it is less prone to staining. It’s typically composed of potassium feldspar, quartz, plagioclase feldspar, biotite, and amphibole, making it a felsic rock (rich in silicon and aluminum). Famous granite formations include Devil’s Tower National Monument in Wyoming and Mount Rushmore in South Dakota.