sedimentary

Chert (Arrowhead/Projectile Point)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan, brown, and grey with possible patination; Luster: Waxy to dull; Breakage: Conchoidal fracture; Structure: Cryptocrystalline; Non-porous.

Hardness: 7 (Mohs scale)
Color: Tan, brown, and grey with possible patination
Luster: Waxy to dull

Identified July 5, 2026More sedimentary →

Explore Chert (Arrowhead/Projectile Point) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 (Mohs scale); Color: Tan, brown, and grey with possible patination; Luster: Waxy to dull; Breakage: Conchoidal fracture; Structure: Cryptocrystalline; Non-porous.

Formation & geological history

Formed as nodules or beds in sedimentary rocks through the precipitation of silica from groundwater or accumulation of siliceous organisms (diatoms/radiolarians). This specific specimen was later knapped by humans during the Archaic or Woodland periods.

Uses & applications

Historically used for hunting (projectile points) and domestic tools (scrapers, knives). Today, they are highly valued by archaeological collectors and for educational purposes.

Geological facts

Chert and flint were preferred by prehistoric peoples because they fracture predictably (conchoidal), creating razor-sharp edges. Ancient 'quarries' for these stones are still being studied by archaeologists today.

Field identification & locations

Identify in the field by looking for 'flake scars' (rippled depressions) from percussion or pressure flaking. Often found in freshly plowed fields, creek beds, or near caves. Federal and local laws often protect artifacts; always check regulations before collecting.