Granite

Physical Properties

Hardness: 6-7 on Mohs scale. Color: Gray, white, and pinkish speckles. Luster: Dull to vitreous (pearly on feldspar faces). Crystal structure: Phaneritic (coarse-grained). Cleavage: None (rock-wide), but individual minerals exhibit specific cleavage. Specific Gravity: 2.63 to 2.75.

Formation & Geological History

Formed from the slow crystallization of magma below Earth's surface (intrusive). Most granites are associated with mountain-building events and range from the Precambrian to Cenozoic eras.

Uses & Applications

Extensively used in construction (countertops, floor tiles, paving stones), monuments, and as crushed stone for road base.

Geological Facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. Commonly found in mountainous regions or shield areas. It is one of the most common rocks on Earth.

Identified on: 4/14/2026

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