sedimentary

Chert (Red Jasper variant)

Silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brick red to brownish-red; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Brick red to brownish-red
Luster: Dull to waxy

Identified July 8, 2026More sedimentary →

Explore Chert (Red Jasper variant) 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: Brick red to brownish-red; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or volcanic environments, later lithified into dense rock. Often found in nodules within limestone or as bedded deposits.

Uses & applications

Historically used for stone tools (knapping); currently used for jewelry, lapidary cabochons, landscaping, and industrial abrasives.

Geological facts

Red chert is often called Jasper when it is opaque and colored by iron inclusions. It has been used by humans for hundreds of thousands of years to create sharp-edged tools due to its predictable conchoidal fracturing.

Field identification & locations

Identify in the field by its high hardness (scratches glass), smooth waxy feel, and characteristic shell-like (conchoidal) curved breakage patterns. Commonly found in river beds or eroded sedimentary outcrops.