sedimentary
Chert (Green Chert or Jasper)
Silicon Dioxide (SiO2)
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 More sedimentary →
Explore Chert (Green Chert or Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary