Chert

Physical Properties

Hardness 6.5-7 on Mohs scale, typically occurs in massive form. Conchoidal fracture. Color can vary widely; this piece shows tan, light brown, and gray hues. Waxy to dull luster.

Formation & Geological History

Formed as a chemical sedimentary rock, typically from the precipitation of silica from groundwater or oceanic water, often replacing other minerals or organic material.

Uses & Applications

Historically used for making stone tools (arrowheads, scrapers) due to its conchoidal fracture. Sometimes used as a low-grade road material or collected as a specimen.

Geological Facts

Flint is a type of chert that occurs specifically in chalk or marly limestone deposits. The sharp edges produced when fractured made it invaluable to early humans.

Field Identification & Locations

Identified by its waxy luster, hardness (scratches glass), and conchoidal fracture. Often found as nodules in limestone or as layered deposits. Look for smooth, curved broken surfaces.

Identified on: 4/26/2026

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