sedimentary

Chert (often called Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with reddish staining; Luster: Waxy to dull; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Tan, brown, and grey with reddish staining
Luster: Waxy to dull

Identified April 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine or groundwater environments. This specimen appears as a nodule or thick bed fragment.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp edges; used today as a road aggregate, in jewelry (as jasper), and for fire-starting (flint).

Geological facts

Chert was one of the first materials traded globally by early humans. It is so hard that it can scratch glass and steel. It often contains micro-fossils only visible under a microscope.

Field identification & locations

Identified in the field by its smooth, shell-like (conchoidal) fracture surfaces and its extreme hardness. Look for it in limestone layers or as rounded river cobbles.