sedimentary

Brown chert (likely flint)

Microcrystalline quartz (SiO₂), chiefly chalcedony

AI-generated identification · may be incorrect

Opaque brown, dull to waxy surface with sharp, curved conchoidal fracture; Mohs hardness about 7, trigonal quartz structure, no cleavage. The image suggests a naturally fractured piece, though exact identification requires examination.

Identified October 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms as silica-rich nodules or layers in sedimentary rocks, often replacing carbonate sediment; the specimen’s age and source cannot be determined from the photo.

Uses & applications

Historically used for tools and fire-starting; today collected, used for knapping, and occasionally fashioned into jewelry.

Geological facts

Chert fractures into sharp edges, making it an important prehistoric tool material.

Field identification & locations

Look for hardness near 7, a waxy appearance, and conchoidal fracture; common in limestone and chalk deposits worldwide. This small rough fragment has an estimated value of about $1–$10.