sedimentary

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Brownish-red, tan, and waxy orange. Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brownish-red, tan, and waxy orange
Luster: Vitreous to waxy

Identified June 4, 2026More sedimentary →

Explore Chert (Jasper/Agate variety) 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 on Mohs scale. Color: Brownish-red, tan, and waxy orange. Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Formation & geological history

Forms primarily as a biochemical or chemical sedimentary rock through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in limestone/dolomite host rocks. This specimen likely developed through groundwater precipitation within sedimentary cavities.

Uses & applications

Used historically for stone tools due to its sharp edges when fractured. Modern uses include decorative landscaping, lapidary work (cabochons), and as a minor abrasive.

Geological facts

Chert is so hard it can create sparks when struck against steel, which made it vital for flintlock firearms. Because of its durability, it often outlasts the host rock it formed in, leading to large 'nodules' found in riverbeds.

Field identification & locations

Identify in the field by its distinctive conchoidal (shell-like) fracture edges, waxy texture, and extreme hardness (it will scratch glass). Commonly found in sedimentary basins and as river-worn cobbles.