Igneous rocks are surprisingly common in Utah. The most common is granite, which is found throughout the state. Granite is an in extrusive rock, meaning that it is formed deep within the earth, and the magma forming it has cooled slowly, allowing large crystals to form. After many millennia of erosion, the rock that was once deep below the surface is now quite near the surface and available for mining. As a result, many historic buildings in the state are made of or contain granite. Granite is used commonly for countertops in homes and for educational and commercial buildings.
The interior of the Utah County Courthouse (151 South University Avenue, Provo) has granite facing. The stone came from Little Cottonwood Canyon and is similar to the granite used to build the Salt Lake Temple.
The Tanner Building on BYU campus (490 Tanner Building, Provo) is also made of granite.
Early Native Americans used obsidian (a glassy, intrusive igneous rock) that they found and mined for arrowheads and for trading.
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