sedimentary

Chert or silicified rock fragment

Microcrystalline quartz (SiO₂), likely chert with iron-oxide staining

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, dull to waxy luster, white-gray to brown/orange coloration, and conchoidal to irregular fracture; no visible cleavage. The specimen appears brecciated or heavily fractured, with rusty limonite/goethite staining and possible weathered host material.

Identified September 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich groundwater replaces or precipitates within sediment, commonly from biogenic silica or volcanic ash. Its exact geological age cannot be determined from the photograph; formation may range from Paleozoic to Cenozoic depending on locality.

Uses & applications

Used historically for sharp-edged tools and occasionally as aggregate or decorative stone; attractive polished pieces may be collected, though this fragment appears mainly of modest specimen value.

Geological facts

The orange-brown colors commonly result from iron oxides and hydroxides occupying fractures and pores. Chert can resemble jasper, but jasper is generally more opaque and strongly colored.

Field identification & locations

Identify it by its very hard, silica-rich character, waxy surface, and glasslike fracture; it should scratch ordinary glass. Common occurrences include limestone beds, volcanic terrains, river gravels, and weathered silica-rich deposits.