sedimentary

Chert (specifically Chalcedony or Flint variation)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brownish-tan to waxen honey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brownish-tan to waxen honey
Luster: Waxy to vitreous

Identified March 4, 2026More sedimentary →

Explore Chert (specifically Chalcedony or Flint variation) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Brownish-tan to waxen honey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation from groundwater within limestone or chalk beds. Most specimens found in decorative gravel date from the Cretaceous period to the Paleozoic.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges; modernly used in road construction, as an abrasive, and sometimes tumbled for jewelry or landscaping.

Geological facts

Because it breaks with a conchoidal (shell-like) fracture, it was the primary material for arrowheads and spear points for thousands of years. It is essentially a non-banded form of agate.

Field identification & locations

Identify in the field by its 'waxy' appearance and smooth, curved break patterns. Common in riverbeds and glacial till. To test, it should be hard enough to scratch glass easily.