sedimentary

Iron-stained chert or silicified ironstone

Microcrystalline quartz (SiO₂), likely limonite/goethite-bearing chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, ochre, gray, and black coloration with earthy to waxy luster and irregular conchoidal-looking fractures. Dense, fine-grained, and lacking visible cleavage; iron oxides produce the rusty staining and metallic-looking patches.

Identified August 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids replaced or cemented sediment, with later oxidation producing limonite and goethite. The exact geological age cannot be determined from the photograph; such material occurs from Precambrian through recent deposits.

Uses & applications

Used locally as aggregate, road material, or decorative stone; attractive pieces may be polished as lapidary specimens. It has modest jewelry and collector appeal unless it displays distinctive fossils, banding, or unusually vivid colors.

Geological facts

The glossy surface may be natural weathering or human polishing. A strong steel scratch should generally fail to mark fresh quartz-rich surfaces, while iron-rich earthy areas may be softer.

Field identification & locations

Common in iron-rich sedimentary terrains, stream gravels, and weathered outcrops worldwide. Confirm with a fresh break, streak test, hardness test, and ideally silica/iron-mineral analysis; the image alone cannot establish a precise species.