sedimentary

Tumbled chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque tan, orange-brown, and cream coloration with a dull-to-waxy luster and very fine cryptocrystalline quartz texture. No visible cleavage; typically conchoidal fracture, though tumbling has rounded the edges.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich material replaces or accumulates in sedimentary settings; jasper is an iron-rich opaque variety. The specimen’s exact geological age and source cannot be determined from the photograph; its rounded form indicates natural water wear or tumbling.

Uses & applications

Used as decorative stone, lapidary material, beads, cabochons, and occasionally toolstone; attractive examples are collected but generally inexpensive.

Geological facts

Chert and jasper can look similar; jasper is commonly red, yellow, or brown from iron oxides, while chert may be gray, cream, or multicolored.

Field identification & locations

Identify by its glassy-to-waxy appearance, lack of visible grains, high hardness, and inability to scratch with a steel knife easily; common in river gravels and sedimentary formations worldwide.