River Pebbles (Sandstone and Quartzite)

Physical Properties

Hardness: 6-7 (Mohs/Quartz based), Color: Grey, tan, buff, and reddish-brown, Luster: Dull to matte (waxy when wet), Structure: Granular or microcrystalline, Cleavage: None/Conchoidal fractures, Specific Gravity: 2.6 - 2.8

Formation & Geological History

Formed through the accumulation of sand grains (sandstone) or the heat/pressure alteration of sandstone (quartzite). These specimens have been smoothed and rounded by high-energy water transport (fluvial or beach action) over many years.

Uses & Applications

Landscaping, drainage control, decorative aquarium use, small-scale construction aggregate, and as 'pocket stones' for casual collectors.

Geological Facts

River stones can travel hundreds of miles from their geological source. Their perfectly rounded shape is a direct result of 'abrasion'—the grinding of stones against each other in moving water.

Field Identification & Locations

Identify in the field by their smooth, rounded edges and lack of sharp corners. They are ubiquitous in riverbeds, glacial deposits, and coastal shorelines. Collectors look for unique patterns or colors within the smoothness.

Identified on: 4/16/2026

Mode: Standard