sedimentary

Chert (flint), possibly a fossil-bearing nodule

Microcrystalline quartz (SiO₂), variety chert

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7; the specimen is gray-white with tan weathering, waxy to dull luster, and conchoidal-looking fractures. Its microscopic quartz crystals are too small to see; no distinct cleavage.

Identified October 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica precipitates or replaces material in sedimentary rocks, often on ancient sea floors. The specimen’s age and exact formation environment cannot be determined from the image.

Uses & applications

Chert has historically been used for tools and fire-starting; attractive pieces are collected or made into ornaments. It has limited modern industrial use.

Geological facts

Chert can resemble agate, chalcedony, or fossil material; the pale, irregular surface alone does not establish that it contains a fossil.

Field identification & locations

Look for hardness near 7, a glassy or waxy surface, and sharp, curved fracture faces. Chert occurs worldwide in sedimentary layers and nodules; locality and a fresh break help refine identification.