Chert (Jasper/Flint variant)

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, brown, and honey-orange; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & Geological History

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone as nodules or bedded layers across various geological ages from Precambrian to Cenozoic.

Uses & Applications

Historically used for stone tools and arrowheads due to its sharp edges; modernly used in construction aggregate, as decorative stones, or for jewelry (when high-quality jasper color is present).

Geological Facts

Chert has been used by humans for hundreds of thousands of years to create tools. Because of its extreme hardness and conchoidal fracture pattern, it produces edges sharper than a steel scalpel.

Field Identification & Locations

Identify by its waxy appearance and 'shell-like' curved breaks (conchoidal fracture). It will easily scratch glass and cannot be scratched by a steel knife. Commonly found in riverbeds or eroding out of limestone cliffs.

Identified on: 4/20/2026

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