sedimentary

Chert (Common Opal/Chalcedony variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale). Color: Waxy white to translucent gray. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Waxy white to translucent gray
Luster: Waxy to vitreous

Identified July 5, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale). Color: Waxy white to translucent gray. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Formation & geological history

Forms primarily as nodules or beds in sedimentary rocks through the precipitation of silica-rich fluids. In this region, it is often associated with the Lower Cretaceous or Tertiary sedimentary deposits of the Gulf Coastal Plain.

Uses & applications

Historically used for making stone tools (lithics). Modernly used as road aggregate, architectural stone, or for lapidary tumbling.

Geological facts

This specimen displays a distinct conchoidal (shell-like) fracture pattern characteristic of high-silica stones. The region near 33.0°N, 93.4°W (Southwest Arkansas) is famous for its diverse sedimentary silica variants, including novaculite and chert.