sedimentary

Rounded brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely ferruginous chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque reddish-brown to brown, dull-to-waxy luster, very fine cryptocrystalline structure, no visible cleavage, and typically conchoidal fracture. Its smooth shape indicates water abrasion or tumbling.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or lithify sediments, often from biogenic silica; iron oxides create the brown-red color. The specimen’s exact geological age cannot be determined visually and may range from Paleozoic to recent gravel deposits.

Uses & applications

Commonly used as aggregate, road material, landscaping stone, and occasionally as a lapidary material for cabochons, beads, or tumbled stones.

Geological facts

Chert can produce an exceptionally sharp edge when fractured and was widely used for prehistoric tools and fire-starting. Jasper is the opaque, impure, iron-colored variety of microcrystalline quartz.

Field identification & locations

Look for a uniform fine texture, waxy surface, high hardness, and conchoidal chips; it should scratch glass but not be scratched by a steel knife. Common in river gravels, glacial deposits, and sedimentary terrains worldwide.