Granite

Physical Properties

Hardness (Mohs scale): 6 to 7; Color: Salt and pepper (white, gray, black, pink); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: None (though constituent minerals like mica and feldspar have it); Specific gravity: 2.63 - 2.75

Formation & Geological History

Formed through the slow crystallization of magma below the Earth's surface (intrusive). They can be found in mountain belts and continental crust spanning billions of years to the present day.

Uses & Applications

Extensively used in construction for countertops, floor tiles, paving stone, 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 granite batholith in the Black Hills of South Dakota.

Field Identification & Locations

Identify in the field by its speckled appearance and interlocking coarse crystals of quartz and feldspar. It is commonly found in the cores of mountain ranges and shield areas of continents.

Identified on: 4/24/2026

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