sedimentary

Chert (Green Chert or Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Dark green with yellow/brown iron staining; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (Conchoidal fracture)

Hardness: 6
Color: Dark green with yellow/brown iron staining
Luster: Waxy to dull

Identified June 28, 2026More sedimentary →

Explore Chert (Green Chert or Jasper) in the encyclopedia →

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: Dark green with yellow/brown iron staining; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (Conchoidal fracture)

Formation & geological history

Formed as a chemical precipitate or by the replacement of carbonate rocks by silica-rich fluids. Often associated with ancient deep-sea deposits or volcanic hydrothermal activity.

Uses & applications

Historically used for making stone tools (arrowheads). Currently used as decorative landscaping stone, in lapidary work for cabochons, and as a collector's specimen.

Geological facts

Chert is so hard it can produce sparks when struck against steel. The green color is typically caused by the presence of chlorite or celadonite minerals within the silica matrix.

Field identification & locations

Identify in the field by its waxy texture and shell-like (conchoidal) fracture patterns. It cannot be scratched by a steel knife. Commonly found in riverbeds or as nodules in limestone.