sedimentary

Rounded chert or jasper pebble

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, ochre, cream, and brown coloration with waxy to dull luster, very fine-grained texture, and no visible cleavage. It is dense and typically breaks with conchoidal fracture, though this specimen is naturally water-rounded and wet-polished.

Identified August 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids replaced or cemented fine sediment, commonly in limestone or volcanic-associated settings; iron oxides create the yellow-brown colors. The rounded shape indicates prolonged transport in a stream or gravel deposit; exact age and locality cannot be determined from the image.

Uses & applications

Used as an aggregate, landscaping stone, lapidary material, cabochons, and tumbled stone; attractive patterned jasper may be used in jewelry.

Geological facts

Chert and jasper are varieties of microcrystalline quartz, and their boundary is largely based on opacity, color, and impurities. A steel file should not scratch it, while it can scratch ordinary glass.

Field identification & locations

Common in streambeds worldwide; inspect for conchoidal edges, glass-scratching hardness, and a uniformly cryptocrystalline interior. A precise identification requires a fresh fracture or thin section.