sedimentary

Yellow-brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely iron-stained chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque mustard-yellow to brown, earthy/waxy luster, very fine-grained cryptocrystalline quartz, with no visible cleavage and conchoidal fracture. Its rounded shape indicates natural water abrasion or tumbling.

Identified September 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Silica-rich microcrystalline rock formed by precipitation or replacement in sedimentary environments, commonly later silicified; iron oxides produce the yellow-brown color. Precise age and locality cannot be determined from the image.

Uses & applications

Used as a flaking stone, aggregate, landscaping pebble, lapidary material, and inexpensive cabochons or decorative objects.

Geological facts

Chert and jasper are varieties of microcrystalline quartz; jasper is typically more opaque and strongly colored by impurities. A steel file should scratch it only weakly or not at all, while it can scratch glass.

Field identification & locations

Common in gravel beds, stream deposits, limestone regions, and glacial sediments worldwide. A glassy wax-like surface and conchoidal fracture support identification, but acid testing is generally uninformative.