sedimentary

Chert or jasper fragments

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; orange-red to tan, earthy to waxy luster, opaque, very fine-grained cryptocrystalline quartz with conchoidal fracture and no cleavage. The reddish colors indicate hematite or other iron oxides; pieces are roughly 2–5 cm across.

Identified September 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediment, commonly in marine chemical sediments, volcanic-sedimentary settings, or weathering zones. The specimens are likely Paleozoic–Mesozoic or younger, but age cannot be determined from the photograph.

Uses & applications

Used as aggregate, roadstone, abrasives, and historically for sharp tools; attractive material is cut or polished for cabochons, beads, and decorative objects. Common pieces generally have modest value.

Geological facts

The angular, shell-like fracture and uniform microcrystalline texture distinguish chert from ordinary sandstone. Red jasper is essentially iron-stained chert, though “jasper” is often used commercially for colorful opaque varieties.

Field identification & locations

Common in sedimentary outcrops, gravel beds, stream gravels, and exposed bedrock worldwide; notable sources include the western United States, England, India, Brazil, and Australia. A steel file should barely scratch it, while quartz should not scratch it; a streak test may show a white to pale-brown streak.