Granite is an igneous rock, which means it formed from magma, or melted rock. It forms deep inside the Earth under a mountain or volcano when melted rock cools or crystallizes into solid rock. Over time, wind, ice, and water wear away at the mountain or volcano above it, and the granite is exposed to the surface. Granite is used as a building material because it's a hard stone.

Image credits: main image, © AMNH; Christine Tappen: courtesy of AMNH.