sedimentary

Weathered chert or jasper nodule

Microcrystalline quartz (SiO₂), likely chert/jasper

AI-generated identification · may be incorrect

Typically hardness 6.5–7, vitreous to waxy luster, opaque cream, tan, yellow, and brown coloration, and no visible cleavage; the irregular dark veins may be iron-oxide staining or fractures. Its rounded form suggests stream abrasion and weathering.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or cement sediment, often in limestone or marine sedimentary environments; jasper is an opaque, iron-rich variety. The specimen’s exact geological age cannot be determined from the image.

Uses & applications

Common chert is used for tools, aggregate, and landscaping; attractive jasper is cut and polished for cabochons, carvings, and ornamental objects.

Geological facts

Chert can fracture conchoidally, producing very sharp edges; prehistoric peoples widely used it for spear points and fire-starting. Iron oxides create the yellow, orange, and brown colors.

Field identification & locations

Look for a very hard, fine-grained, waxy material that scratches glass and lacks obvious mineral grains; a fresh broken surface should be smooth and conchoidal. Common in gravel bars, limestone regions, and sedimentary outcrops.