sedimentary

Chert (varietal: Flint/Jasper mix)

Hydrous Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Gray, tan, or brown with possible banding; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6

Hardness: 6
Color: Gray, tan, or brown with possible banding
Luster: Waxy to dull

Identified February 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine or freshwater environments by the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from hydrothermal fluids within sedimentary rock layers.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used as abrasive media, in construction aggregate, and occasionally as decorative landscaping stone or tumbled pocket stones.

Geological facts

Chert has been used by humans for over 2 million years. When struck against steel or other hard minerals, it can produce sparks, making it essential for early fire-making and flintlock firearms.

Field identification & locations

Identify in the field by its very smooth, glass-like fracture surfaces (conchoidal) and its ability to scratch glass. Found globally in limestone or chalk beds. Collectors look for unique banding or 'nodule' shapes.