sedimentary

Chert (Arrowhead variety)

Chert (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Variegated black with white/tan bands; Luster: Waxy to vitreous; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Variegated black with white/tan bands
Luster: Waxy to vitreous

Identified January 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in marine environments. This specimen has been anthropogenically modified through knapping to create a projectile point.

Uses & applications

Historically used for stone tools and weapons due to its predictable conchoidal fracturing. Modernly used in geological research, lapidary arts, and as construction aggregate.

Geological facts

Chert is a high-silica rock that breaks with razor-sharp edges. When it is of particularly high quality and colorful, it is often called flint or jasper. This specific specimen follows a 'corner-notched' design common in ancient projectile technologies.

Field identification & locations

Identify in the field by its smooth, waxy surface and shell-like (conchoidal) fracture scars. It will scratch glass but cannot be scratched by a steel knife. Commonly found in limestone formations or as river-worn nodules.