sedimentary

Banded Chert (or River Jasper)

Microcrystalline Quartz (SiO2) with iron oxide impurities

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs). Color: Tan, brown, white, and yellow banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7. Highly durable and smooth surface texture.

Hardness: 6
Color: Tan, brown, white, and yellow banding
Luster: Waxy to vitreous

Identified June 19, 2026More sedimentary →

Explore Banded Chert (or River Jasper) 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

Formed by the accumulation of silica-rich organic or chemical remains in deep-sea or shallow-water environments. Over millions of years, silica replaces other minerals or fills voids. Weathering and water transport in rivers often round these stones into smooth pebbles.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to sharp edges. Today used for landscaping, rock tumbling, lapidary cabochons, and as a collector's hobby item.

Geological facts

Chert is essentially the same mineral as flint, though 'flint' usually refers to dark nodules in chalk. Banded varieties are often called 'Jasper' by river rock collectors when they display vibrant colors. It is one of the most common rocks used by prehistoric humans.

Field identification & locations

Identified by its extreme hardness (will scratch glass), waxy feel, and smooth curves where it has broken (conchoidal fracture). Commonly found in riverbeds, gravel pits, and coastal eroded areas. Look for the distinct parallel banding patterns.