sedimentary

Iron-stained chert (possibly jasper)

Microcrystalline quartz (SiO₂), colored by iron oxides

AI-generated identification · may be incorrect

Opaque, rusty yellow-brown with darker mottling and a dull to slightly waxy surface. Quartz hardness is about 7 Mohs; chert has no visible crystal structure or cleavage and commonly breaks with a curved, sharp-edged conchoidal fracture. Specific gravity is roughly 2.6.

Identified October 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Silica-rich sediment or replacement material lithified into chert; iron oxides impart the brown-red color. Chert forms in many geologic periods and settings, so age and precise origin cannot be determined from the image alone.

Uses & applications

Chert has historically been used for tools and may be collected or cut as decorative jasper-like material; this specimen appears unpolished and has little commercial value.

Geological facts

Jasper is an iron-rich, opaque variety of microcrystalline quartz, while chert is the broader rock name; the boundary between them is often informal.

Field identification & locations

Look for hardness near 7, a dense fine-grained texture, and sharp conchoidal fractures; rusty coloration alone is not diagnostic. Chert occurs worldwide in sedimentary formations.