sedimentary

Chert (Commonly known as Flint or Jasper when pigmented)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, white, or light brown (as seen in specimen); Luster: Waxy to dull; Crystal structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Tan, beige, white, or light brown (as seen in specimen)
Luster: Waxy to dull

Identified March 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in marine environments. It often forms as nodules in limestone or chalk beds and can range from Precambrian to Holocene in age.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used as road aggregate, in glass manufacturing, and occasionally as semi-precious gemstones or decorative landscaping rocks.

Geological facts

Chert was one of the most important resources for prehistoric humans because it breaks with a conchoidal fracture, creating razor-sharp edges for arrowheads and scrapers. It can even create sparks when struck against steel.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like fracture pattern. It is commonly found globally in sedimentary basins, riverbeds, and as nodules in limestone outcrops.