Granite

Physical Properties

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

Formation & Geological History

Formed through the slow crystallization of magma below the Earth's surface (plutonic). It can take millions of years to cool. Granite is a major component of the continental crust and can range in age from the Precambrian to the Cenozoic.

Uses & Applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. It is also used as crushed stone (aggregate) for road building and concrete.

Geological Facts

Granite is the most common igneous rock found at the Earth's surface. Mount Rushmore is carved into a massive granite batholith in South Dakota. Because it is so hard and durable, it was the preferred building material for the pyramids of Egypt's internal chambers.

Field Identification & Locations

Identify by its 'salt-and-pepper' appearance and coarse texture. Look for visible crystals of quartz (clear/gray), feldspar (white/pink), and mica (shiny black/silver). It is found worldwide in mountain ranges and Shields (like the Canadian Shield).

Identified on: 4/25/2026

Mode: Standard