sedimentary

Chert (Arrowhead Preform or Flake)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Variegated brown, grey, and ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Variegated brown, grey, and ochre
Luster: Waxy to dull

Identified April 12, 2026More sedimentary →

Explore Chert (Arrowhead Preform or Flake) 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: Variegated brown, grey, and ochre; Luster: Waxy to dull; Crystal structure: 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 sedimentary environments. This specimen shows signs of hydration or iron staining from secondary mineral deposition.

Uses & applications

Historically used for stone tools (lithics) due to its sharp conchoidal fracture. Today used as a collector's specimen or for lapidary work.

Geological facts

This piece appears to be a 'preform' or a lithic flake, meaning it may have been handled or shaped by early humans for the purpose of making a tool. Its tapered shape is classic for tool-making debris.

Field identification & locations

Identify by its waxy texture, extreme hardness (it will scratch glass), and shell-like (conchoidal) fractures. Common in riverbeds and limestone outcrops. Look for 'bulb of percussion' or ripple marks on the surface which indicate it was struck.