sedimentary

Chert (Common Variety, Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, brown, and grey banding; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Tan, brown, and grey banding
Luster: Waxy to dull

Identified February 21, 2026More sedimentary →

Explore Chert (Common Variety, 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: Tan, brown, and grey banding; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed primarily as a chemical precipitate from silica-rich fluids or the accumulation of siliceous skeletal remains (diatoms, radiolarians) in marine environments. This specimen appears water-worn, likely from a fluvial (river) deposit.

Uses & applications

Used historically for stone tools and arrowheads due to its sharp fracture; currently used in construction as aggregate and as a low-cost lapidary material for tumbling.

Geological facts

Chert has been used by humans for over 2 million years. Its waxy texture and ability to produce razor-sharp edges made it the primary material for the Stone Age tool industry.

Field identification & locations

Identify in the field by its hardness (will scratch glass), waxy appearance, and smooth, curved (conchoidal) fractures. Often found in riverbeds or as nodules within limestone formations.