sedimentary

Chert (often called Jasper or Flint in this color variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Variegated red, grey, green, and brown; Luster: Vitreous to waxy; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 (Mohs scale)
Color: Variegated red, grey, green, and brown
Luster: Vitreous to waxy

Identified April 12, 2026More sedimentary →

Explore Chert (often called Jasper or Flint in this color variety) 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 from the recrystallization of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from silica-rich fluids in sedimentary layers or volcanic cavities.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used as decorative stones, gemstones (as Jasper), and in some industrial grinding applications.

Geological facts

Because of its conchoidal fracture (breaking like glass with sharp edges), it was the primary material for prehistoric toolmaking globally for thousands of years.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy luster, and curved 'scalloped' fracture edges. Commonly found in limestone beds or as nodules in volcanic soil.