sedimentary

Iron-stained chert or jasper pebble

Microcrystalline quartz (SiO₂), likely hematite/goethite-bearing

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; reddish-brown, gray-green, and cream colors; dull to waxy luster; very fine-grained, massive structure with no visible cleavage. The rounded surface indicates stream abrasion, and the dark glossy edge may be a fresh conchoidal fracture.

Identified August 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely silica-rich sediment that lithified as chert and was later colored by iron oxides during weathering. Such pebbles may range from Paleozoic to younger source-rock ages and are commonly reworked into Quaternary river or glacial gravels near 48.5°N, 122.3°W.

Uses & applications

Used mainly as a lapidary, carving, and tumbling material; attractive jasper varieties are used for cabochons and decorative objects. Ordinary pieces have little commercial value.

Geological facts

The image supports a chert/jasper identification, but distinguishing jasper from iron-stained volcanic rock requires a scratch or fracture test. Quartz-rich material commonly produces a sharp, curved fracture rather than flat cleavage.

Field identification & locations

Common in Pacific Northwest stream and glacial gravels, including material derived from volcanic and sedimentary formations. It should scratch glass, resist a steel knife, and show no fizz with dilute hydrochloric acid; a streak test may show a reddish-brown iron-oxide streak.