sedimentary

Chert (Nodular Chert)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Tan, brown, or ochre; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs scale
Color: Tan, brown, or ochre
Luster: Dull to waxy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Tan, brown, or ochre; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed by the accumulation and lithification of silica-rich materials, typically in marine environments where silica replaces carbonate minerals or precipitates from groundwater. Common in limestone and dolostone formations.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to its conchoidal fracture. Today used as road base, construction aggregate, and occasionally for lapidary work.

Geological facts

Chert is essentially the same chemical composition as flint and Jasper; the names are often used interchangeably depending on color and regional preference. It is chemically very stable and resistant to weathering.

Field identification & locations

Identify in the field by its superior hardness (cannot be scratched by steel) and curved, glass-like fracture surfaces. Often found as rounded nodules or distinct layers within softer limestone cliffs.