River Pebble (Quartz/Jasper)

Physical Properties

Hardness: 6.5-7.0 (Mohs scale), Color: tan, brown, or earthy mottled tones, Luster: Waxy or dull when found, glassy when polished, Crystal structure: Microcrystalline, Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed through the accumulation of silica-rich material in sedimentary environments or as secondary fill in volcanic rocks. This specific specimen has been chemically and mechanically weathered into a smooth rounded shape by water transport in a river or beach environment.

Uses & Applications

Common pebbles are used in decorative landscaping, as river rock, in construction aggregates, and small polished versions (tumbled stones) are popular for beginner rock collectors.

Geological Facts

The rounding of a pebble is called 'clast rounding' and is a direct result of the distance and energy of the water that carried it. This specimen likely lived in a riverbed for thousands of years to achieve this shape.

Field Identification & Locations

Identify in the field by its smooth, rounded surface and high hardness (cannot be scratched by a steel knife). Commonly found in riverbeds, glacial deposits, and along coastlines worldwide.

Identified on: 4/22/2026

Mode: Standard