sedimentary

Chert (Cherty Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: typically gray, brown, or tan with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (systemic conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: typically gray, brown, or tan with waxy luster

Identified March 24, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: typically gray, brown, or tan with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (systemic conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within limestone or chalk beds. Often dated from the Paleozoic to Mesozoic eras.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used in construction aggregate, road surfacing, and as a low-cost gemstone for tumbling or lapidary practice.

Geological facts

Chert exhibits conchoidal fracture, meaning it breaks like glass. It was one of the most vital materials for early humans to create arrowheads and scrapers. Some varieties including 'Jasper' and 'Agate' are essentially colorful forms of chert.

Field identification & locations

Identify in the field by its smooth, waxy feel and the way it produces scalloped, razor-sharp edges when chipped. It is commonly found in riverbeds, glacial till, and embedded in limestone outcrops. It will scratch glass easily.