sedimentary

Chert (Arrowhead artifact)

Chert (Cryptocrystalline Silica, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy; Luster: Vitreous to waxy; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Brown, tan, waxy
Luster: Vitreous to waxy

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy; Luster: Vitreous to waxy; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed as a chemical precipitate or biochemical deposit in sedimentary rock units, often as nodules in limestone or chalk. This specific specimen has been anthropogenically modified through knapping.

Uses & applications

Historically used for stone tools and weapons (lithics); currently of archaeological, historical, and collecting interest.

Geological facts

Chert and flint were among the first resources used by early humans to create sharp-edged tools due to their predictable conchoidal fracturing patterns.

Field identification & locations

Identify in the field by its waxy texture, hardness (cannot be scratched by steel), and sharp, shell-like fracture edges. Found worldwide in sedimentary basins.