Granite Cobble

Physical Properties

Hardness: 6-7 (Mohs); Color: Tan, beige, and orange with black flecks; Luster: Vitreous to dull; Structure: Phaneritic (visible crystals); Cleavage: None (fractures irregularly); Specific gravity: 2.63-2.75

Formation & Geological History

Formed from the slow cooling and crystallization of felsic magma beneath the Earth's surface. This specific specimen has been polished into a rounded shape by river or beach water action over thousands of years.

Uses & Applications

Granite is used extensively in construction, countertops, and floor tiles. Cobble-sized pieces like this are often used in landscaping or as decorative garden stones.

Geological Facts

Granite is one of the most common rocks in the Earth's continental crust. It contains quartz, feldspar, and mica (the black flecks seen here are likely biotite or hornblende).

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and hardness (cannot be scratched by a steel knife). Commonly found in mountainous regions or as displaced glacial erratics and river rocks.

Identified on: 5/3/2026

Mode: Standard