sedimentary

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, gray, and blue-green; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, gray, and blue-green
Luster: Vitreous to waxy

Identified June 21, 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: Reddish-brown, gray, and blue-green; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich fluids in limestone or volcanic rock cavities. Often occurs as nodules or replacement deposits. Geological age varies greatly from Precambrian to Cenozoic.

Uses & applications

Used historically for stone tools and weapons due to its sharp edges; modern uses include lapidary work, jewelry, and landscaping. High-quality specimens are popular among rockhounds.

Geological facts

This specimen shows transitions between opaque jasper and translucent chalcedony. Historically, chert was a primary material for making arrowheads and spear points because of its predictable fracturing patterns.

Field identification & locations

Identify by its 'shell-like' shell-like (conchoidal) fracture and its ability to scratch glass. Commonly found in stream beds, gravel pits, and sedimentary rock outcrops. Collectors should look for unique banding or color inclusions.