sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Mohs hardness: 6.5-7; Color: Olive green to brownish-green with iron oxide streaks; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Hardness: 6
Color: Olive green to brownish-green with iron oxide streaks
Luster: Waxy to vitreous

Identified June 25, 2026More sedimentary →

Explore Chert (Jasper/Flint 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 primarily by the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation in marine environments. This specimen shows signs of river or stream tumbling, giving it a smooth, rounded water-worn texture.

Uses & applications

Historically used for stone tools and weapons due to its sharp conchoidal fracture. Currently used in lapidary work, jewelry, landscaping, and as a decorative collector's item.

Geological facts

Chert is so durable that it often survives long after the rock matrix it formed in has eroded away. It is often found in riverbeds and on beaches worldwide.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel, and characteristic shell-like (conchoidal) fractures where it has chipped. Common in limestone regions and gravel deposits.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary