Granite River Pebble

Physical Properties

Hardness: 6–7 on Mohs scale; Color: Mottled salt-and-pepper (white, grey, tan, and black); Luster: Dull/earthy (weathered) to vitreous (on fresh surfaces); Crystal structure: Phaneritic (coarse-grained crystals); Specific gravity: approx. 2.63 to 2.75.

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface. This specific specimen has been chemically and physically weathered and rounded by water transport in a river or coastal environment, likely over thousands of years.

Uses & Applications

River pebbles are used in landscaping, decorative ground cover, and as aggregate in high-strength concrete. Large granite deposits are used for countertops, monuments, and paving.

Geological Facts

Granite makes up a large portion of the Earth's continental crust. Because of its high quartz content, it is extremely resistant to erosion, which is why granite pebbles often survive long journeys downstream while softer rocks disintegrate.

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally in riverbeds, glacial tills, and mountainous regions. It cannot be scratched by a steel knife.

Identified on: 4/27/2026

Mode: Standard