sedimentary

Water-worn brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely ferruginous chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, olive, and reddish mottling from iron oxides; dull to waxy luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The rounded shape indicates stream abrasion.

Identified August 10, 2026More sedimentary →

Explore Water-worn brown chert or jasper pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms when silica replaces or cements sediment, commonly with iron-oxide staining; chert deposits range from Precambrian to Cenozoic in age. This specimen was likely transported and rounded in a freshwater stream.

Uses & applications

Used locally as durable aggregate, road material, landscaping stone, and historically for toolmaking; attractive jasper varieties are polished for cabochons and collectibles. This small natural pebble has limited commercial value.

Geological facts

Chert and jasper are varieties of microcrystalline quartz; jasper is typically opaque and impurity-rich, while chert may be more uniformly gray or translucent. Surface wetness intensifies its colors and gloss.

Field identification & locations

Look for hardness, opaque earthy coloration, waxy texture, and conchoidal chips; it should scratch glass but not be scratched by a steel blade. Common in gravel bars worldwide, especially near sedimentary or volcanic terrains.