sedimentary

Likely ironstone or weathered chert with an iron-oxide spot

Silicified sedimentary rock, possibly ferruginous chert (microcrystalline SiO₂ with Fe oxides)

AI-generated identification · may be incorrect

Brown, opaque, fine-grained and dull to slightly waxy; the orange patch is likely limonite/goethite or another iron oxide. Expected hardness is about 6–7 if cherty, with no visible cleavage; exact identification requires streak, hardness, and specific-gravity tests.

Identified September 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably formed from silica-rich sediment later cemented or replaced, with iron-bearing fluids producing the orange inclusion and brown weathering. Its precise geological age cannot be determined from the photograph.

Uses & applications

Common pieces have little industrial or jewelry use, though attractive examples may be used as lapidary cabochons, curiosities, or teaching specimens.

Geological facts

The contrasting orange area may be a secondary mineral filling a pore or fracture rather than a true crystal. A magnet test may detect associated magnetite, but limonite/goethite is usually nonmagnetic.

Field identification & locations

Look for a glassy/waxy fracture, resistance to scratching by a steel blade, and a white-to-brown streak; fizzing in dilute acid would suggest carbonate rather than chert. Similar ferruginous cherts occur worldwide, including sedimentary iron-rich formations.