sedimentary

Chert (containing Quartz)

Microcrystalline Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on the Mohs scale; Color: Grey, tan, and translucent white patches; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Grey, tan, and translucent white patches
Luster: Waxy to dull

Identified March 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of silica-rich fluids within sedimentary rock layers like limestone or through the accumulation of siliceous remains such as diatoms or radiolarians. Often found in Phanerozoic era strata.

Uses & applications

Historically used for stone tools (arrowheads) due to its sharp edges; modernly used as road aggregate, in glass manufacturing, and as a durable material for tumbling and craft jewelry.

Geological facts

Chert has a distinct sharp edge when broken, leading to its widespread use in prehistoric toolmaking. It is one of the most chemically stable and weather-resistant sedimentary rocks.

Field identification & locations

Identify in the field by its conchoidal (shell-like) fracture pattern and the fact that it can scratch glass easily. Commonly found in riverbeds, limestone outcroppings, and coastal gravels.