sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs), Color: reddish-brown and grayish-tan bands, Luster: dull to waxy/greasy, Crystal structure: Microcrystalline (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Hardness: 6

Identified June 30, 2026More sedimentary →

Explore Chert (Jasper) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation from silica-rich fluids within sedimentary rock layers. Its banded appearance suggests varying mineral content during deposition.

Uses & applications

Used historically for stone tools and weapons due to its sharp edges; currently used for lapidary work, jewelry (cabochons), and as a decorative landscaping stone.

Geological facts

This specimen shows distinct banding, often referred to as 'ribbon chert' or 'striped jasper.' Jasper is essentially an opaque variety of chert colored by iron impurities.

Field identification & locations

Identify in the field by its hardness (it can scratch glass and steel), conchoidal fracture (smooth, curved breaks), and lack of reaction to acid. Often found in riverbeds or coastal cliffs.