sedimentary

Chert (Green variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Olive green; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Olive green
Luster: Waxy to dull

Identified May 23, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 Mohs; Color: Olive green; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or sponges) or chemical precipitation in marine environments. This specimen appears as a flake or fragment from a larger nodule.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to its sharp conchoidal fracture. Modernly used as an ornamental stone or in some industrial abrasive applications.

Geological facts

This specific piece shows signs of flaking, which is characteristic of 'lithic debitage'—the waste material produced when ancient peoples crafted stone tools.

Field identification & locations

Identify by its waxy texture, inability to be scratched by steel, and sharp, shell-like (conchoidal) edges. Found worldwide in limestone and chalk beds.