sedimentary

Weathered iron-rich chert or siliceous breccia

Microcrystalline quartz (SiO₂), likely with iron oxides and minor clay minerals

AI-generated identification · may be incorrect

Hardness about 6.5–7; tan, gray, brown, and rusty-red mottling; dull to waxy luster; cryptocrystalline, massive texture with no obvious cleavage. The rough, weathered surface and possible angular fragments suggest chert or silicified breccia.

Identified August 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably formed when silica-rich groundwater replaced or cemented sediment, with later iron-oxide staining during weathering. Its exact geological age and locality cannot be determined from the photograph.

Uses & applications

Mostly a collecting specimen; chert can be used for prehistoric tools, aggregate, and decorative stone, though this piece appears too small and irregular for commercial use.

Geological facts

Chert commonly forms nodules or beds in limestone and other sedimentary sequences. Iron minerals produce the yellow-brown to reddish coloration through oxidation.

Field identification & locations

Test for a glassy conchoidal fracture and inability to scratch it with a steel knife; it may scratch ordinary glass. A streak test, acid test, and thin-section or elemental analysis would distinguish chert from weathered volcanic rock or ironstone.