Granite

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white, gray, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral (feldspar has 2 planes at 90 degrees); Specific Gravity: 2.63 to 2.75

Formation & Geological History

Formed through the slow crystallization of silica-rich magma below the Earth's surface (intrusive). They can range from Precambrian to Cenozoic in age and are found in continental crustal plates.

Uses & Applications

Extensively used in construction for countertops, floor tiles, paving stone, curbing, and monumental architecture. High-quality specimens are used in sculpture and interior design.

Geological Facts

Granite is the most common igneous rock found at the Earth's surface and makes up the bulk of the continental crust. Mount Rushmore is carved into a large granite batholith called the Harney Peak Granite.

Field Identification & Locations

Identify in the field by its coarse-grained 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It is found in large mountain ranges and shield areas globally.

Identified on: 5/1/2026

Mode: Standard