sedimentary

Chert (Green Chert)

Microcrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: olive green, tan, and brown mottled; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: olive green, tan, and brown mottled
Luster: waxy to dull

Identified June 24, 2026More sedimentary →

Explore Chert (Green Chert) 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 on Mohs scale; Color: olive green, tan, and brown mottled; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed via the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads); currently used as river rock for landscaping, as an abrasive, and occasionally for lapidary work or semi-precious jewelry.

Geological facts

Chert is so hard it can strike sparks against steel. The green color is often caused by the presence of minerals like chlorite or celadonite within the silica matrix.

Field identification & locations

Identify in the field by its smooth, waxy texture when wet, high hardness (cannot be scratched by a steel knife), and characteristic curved (conchoidal) fractures. Common in riverbeds and limestone outcrops.