sedimentary

Polished iron-stained chert or jasper pebble

Microcrystalline quartz (SiO₂), likely ferruginous chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; mustard-yellow to brown with iron-oxide staining, dull to waxy luster, and a smooth conchoidal fracture surface. It appears rounded and polished, with dark curved internal bands or fractures; no visible crystal cleavage.

Identified September 21, 2026More sedimentary →

Explore Polished iron-stained 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

Chert forms when silica-rich fluids replace or cement sediments, commonly from biological silica or volcanic ash; iron oxides create the yellow-brown coloration. Its exact geological age cannot be determined from the photograph and may range from Paleozoic to recent alluvial reworking.

Uses & applications

Used as a decorative pebble, cabochon, carving material, and lapidary stone; historically, chert was knapped for tools and fire-starting. It has limited industrial value compared with ordinary quartz or flint.

Geological facts

The specimen may be called jasper if the opaque, iron-rich material is dominant, or chert if it is chiefly silica with finer texture. The curved markings likely reflect natural fracture, banding, or surface weathering rather than fossils.

Field identification & locations

Common in river gravels and sedimentary terrains worldwide, especially areas with iron-rich chert or jasper. A steel-file scratch test should not easily mark it; vinegar has no reaction, distinguishing it from carbonate rocks.