Granite

Physical Properties

Hardness: 6-7 on Mohs scale; Color: Pink, white, and gray speckled; Luster: Vitrous to dull; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Specific gravity: 2.63 to 2.75

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface. This specimen likely originates from a deep-seated pluton that was subsequently exposed by erosion. Ages can range from Precambrian to Cenozoic depending on the tectonic setting.

Uses & Applications

Used extensively in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also a popular material for rock climbing 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. It is one of the hardest and most durable natural stones used by humans since ancient times.

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz (glassy) and feldspar (opaque pink/white). It is common in mountainous regions and continental shields like the Canadian Shield.

Identified on: 4/14/2026

Mode: Standard