Granite

Physical Properties

Hardness: 6-7 Mohs; Color: Mottled brown, tan, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Quartz, Feldspar, and Biotite Mica.

Formation & Geological History

Formed from the slow crystallization of silica-rich magma below the Earth's surface (intrusive). Most granite formations date from the Precambrian to Cenozoic eras.

Uses & Applications

Widely used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as an aggregate in road building.

Geological Facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith, and the rock is famous for its extreme durability and resistance to weathering.

Field Identification & Locations

Identifiable by its 'salt and pepper' or multicrystalline appearance where individual minerals are visible to the naked eye. Commonly found in mountainous regions or shield areas like the Canadian Shield.

Identified on: 4/13/2026

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