sedimentary

Chert (specifically as a lithic artifact/projectile point)

Chert (Silicon dioxide, SiO2)

Hardness: 7 (Mohs scale); Color: Mottled gray, tan, and blue-gray with earthy inclusions; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Mottled gray, tan, and blue-gray with earthy inclusions
Luster: Waxy to dull

Identified March 29, 2026More sedimentary →

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 organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; age varies by deposit, typically Paleozoic to Mesozoic era formations.

Uses & applications

Historically used for tools and weapons due to sharp conchoidal edges; currently valued for archaeological study, flintknapping, and amateur collecting.

Geological facts

This specimen has been worked by humans into a stone tool, known as a 'lithic artifact.' Notice the 'flake scars' where the material was struck to create sharp edges and a notched base for hafting to a shaft.

Field identification & locations

Identify in the field by looking for translucent edges, a 'clinking' sound when tapped, and signs of intentional shaping (flaking). Common in limestone-rich regions of the American Midwest and Southeast.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone (Quartz-rich)

Arenite (SiO2)

sedimentary

Sandstone (with man-made markings)

Arenite (composed primarily of Quartz, SiO2)

sedimentary