sedimentary

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, brown, with dark inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Tan, brown, with dark inclusions
Luster: Waxy to dull

Identified July 15, 2026More sedimentary →

Explore Chert (Jasper 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 Mohs; Color: Tan, brown, with dark inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Forms primarily as nodules or beds in sedimentary rocks through the accumulation of silica-rich fluids or organic remains (like diatoms/radiolarians) that recrystallize over millions of years. Common in limestone and dolostone formations.

Uses & applications

Historically used for stone tools and arrowheads; currently used as decorative gravel, in lapidary work (jewelry), and for building materials. High quality specimens are sought by mineral collectors.

Geological facts

Chert is so hard it can create sparks when struck against steel, which made it a vital survival tool for early humans. It is chemically identical to quartz but has a different internal structure.

Field identification & locations

Identify by its smooth, waxy surface and shell-like (conchoidal) fracture pattern. Look for it in riverbeds or within limestone outcrops. It will scratch glass easily.