sedimentary

Chert (variously identified as Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale. Color: Gray, tan, and white with some veining. Luster: Waxy to dull. Structure: Non-crystalline mass (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6

Hardness: 6
Color: Gray, tan, and white with some veining
Luster: Waxy to dull

Identified March 15, 2026More sedimentary →

Explore Chert (variously identified as Flint) 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 through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from groundwater. This piece appears to be a water-worn river stone or a tumbled fragment from a larger nodule, typically found in limestone or chalk deposits.

Uses & applications

Historically used for stone tools and starting fires (flint). Modernly used in landscaping, road aggregate, and sometimes as low-to-medium grade decorative stones for lapidary work.

Geological facts

Chert is so tough it was the primary material for prehistoric arrowheads and spear tips because it breaks into razor-sharp edges. It is chemically stable and resistant to weathering, which is why it is often found as smooth pebbles in riverbeds.

Field identification & locations

Identify in the field by its conchoidal (shell-like) fracture pattern and the fact that it will scratch glass. This specific specimen’s rounded edges and small size suggest it was collected from a gravel bed or river. Common worldwide.