sedimentary

Iron-rich chert or jasper

Microcrystalline quartz (SiO₂), stained by hematite/goethite

AI-generated identification · may be incorrect

Typically hardness 6.5–7, opaque, reddish-brown to black, with dull to waxy luster and no visible cleavage; the dark areas likely contain iron oxides or manganese minerals. The rounded, weathered surface suggests a natural cobble or nodule.

Identified August 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediment, with later iron-oxide staining; specimens may range from Precambrian to younger sedimentary ages. Common in weathered gravel, river deposits, and iron-rich sedimentary formations.

Uses & applications

Used as decorative stone, lapidary material, aggregate, and occasionally as a source of silica; attractive pieces may be polished for display.

Geological facts

Jasper is an opaque variety of chert, and red coloration is commonly caused by hematite. Exact identification would require a fresh broken surface, streak, and hardness testing.

Field identification & locations

Look for a smooth conchoidal fracture, glassy-to-waxy texture, and inability to scratch it with a steel knife; quartz-rich material scratches glass. Common in gravel beds and areas with iron-bearing rocks.