sedimentary

Chert (within Asphalt)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Tan, beige, brown
Luster: Waxy to dull

Identified March 15, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine or groundwater environments. These specimens are often sourced from river gravels or quarries as aggregate for road construction.

Uses & applications

Used primarily as aggregate in construction, road surfaces (asphalt), and concrete. Historically used for stone tools (arrowheads) due to its sharp conchoidal fracture.

Geological facts

Chert is so hard it can create sparks when struck against steel. Flint is a well-known dark variety of chert. This specific piece is acting as 'aggregate' in a bituminous pavement mixture.

Field identification & locations

Identify by its 'flint-like' waxy texture, smooth curved (conchoidal) breaks, and the fact that it cannot be scratched by a steel knife. Common in limestone regions and as creek bed gravel.