sedimentary

Chert (Green variety)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Pale yellowish-green; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Pale yellowish-green
Luster: Waxy to dull

Identified April 12, 2026More sedimentary →

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: Pale yellowish-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 diatoms or radiolarians) or chemical precipitation from groundwater within sedimentary rock layers. It is often found as nodules in limestone or as bedded deposits.

Uses & applications

Historically used for stone tools due to its sharp edges when fractured. Currently used as a gemstone (jaspers), in landscaping, and as a component in construction aggregate.

Geological facts

Chert is so hard that it can strike sparks against steel. It was one of the most vital materials for early humans to manufacture spearheads, arrowheads, and scrappers.

Field identification & locations

Identify in the field by its waxy appearance, extreme hardness (it will scratch glass), and conchoidal fracture patterns that look like sea shells. Common in limestone outcrops.