Granite

Physical Properties

Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and black (salt and pepper); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (fractures irregularly); Specific gravity: 2.63-2.75

Formation & Geological History

Formed by the slow cooling and crystallization of silica-rich magma deep beneath the Earth's surface (plutonic). Found in continental crust, often dating from the Precambrian to the Cenozoic eras.

Uses & Applications

Used extensively in construction for countertops, floor tiles, paving stones, monuments, and as a crushed stone for road base and concrete aggregate.

Geological Facts

Granite is one of the hardest and most common rocks on Earth. It makes up the core of most mountain ranges. Mount Rushmore is carved into a massive granite batholith in South Dakota.

Field Identification & Locations

Identify by its interlocking 'salt and pepper' crystalline texture where minerals like quartz, feldspar, and mica are large enough to see with the naked eye. It will not scratch with a pocket knife.

Identified on: 5/4/2026

Mode: Standard