sedimentary

Likely flint/chert fragments

Microcrystalline quartz (SiO₂), possibly fossil-bearing chert

AI-generated identification · may be incorrect

Opaque gray-brown, dull to waxy luster, very fine-grained cryptocrystalline structure, conchoidal fracture, no visible cleavage; Mohs hardness about 7 and specific gravity ~2.6. The pieces appear naturally fractured or roughly knapped, though the image alone cannot confirm origin.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica replaces carbonate sediments or accumulates from siliceous biological remains, commonly during diagenesis in marine limestone. It occurs from Precambrian to Recent strata; exact age and source require geological context.

Uses & applications

Historically used for sharp tools and fire-starting; today it is mainly a teaching, archaeological, or lapidary specimen, with limited aggregate use.

Geological facts

Freshly broken chert can produce extremely sharp edges and may show subtle banding, fossils, or iron-oxide staining. It is closely related to flint, with the distinction usually based on color and geological setting.

Field identification & locations

Identify it by testing for glass-scratching hardness, examining waxy fracture surfaces, and checking for bubbles or uniform glassiness that would suggest manufactured glass. Common in limestone regions worldwide, including England, France, the Great Plains, and Texas.