sedimentary

Tumbled chert (likely jasper-bearing chert)

Microcrystalline quartz; SiO₂ (chalcedony/chert)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, reddish, gray, and olive-green coloration with a dull to waxy luster. It has cryptocrystalline quartz, no visible cleavage, and commonly forms smooth conchoidal fractures; the rounded surface indicates tumbling or natural abrasion.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or cement fine sediment, often in marine limestone or volcanic-sediment environments. Its exact age cannot be determined visually; chert occurs from Precambrian rocks through modern deposits.

Uses & applications

Used for tools, flint-like cutting edges, road aggregate, and decorative stone; attractive polished pieces are used in cabochons and low-cost jewelry.

Geological facts

The brown-red tones may reflect iron oxides, while green areas can result from chlorite or other alteration minerals. A sharp edge can produce a conchoidal fracture and the stone should scratch ordinary glass.

Field identification & locations

Common in river gravels, limestone formations, and sedimentary outcrops worldwide; inspect for waxy luster, very fine texture, and glass-like fracture. Exact identification could require a hardness test or thin-section analysis.