sedimentary

Chert (variously known as Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: Tan, beige, light brown, white. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Tan, beige, light brown, white
Luster: Dull to waxy

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Tan, beige, light brown, white. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Formation & geological history

Formed by the precipitation of silica from seawater or groundwater. Commonly occurs as nodules in limestone or chalk beds. Often associated with Precambrian to Holocene geological ages.

Uses & applications

Historically used for stone tools and weapons due to sharp fracture edges. Today used in construction aggregate, road surfacing, and as a decorative stone in landscaping.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture creates edges sharper than a steel scalpel. Native Americans used it extensively for arrowheads.

Field identification & locations

Identify in the field by its hardness (it scrapes steel and glass) and the characteristic curved, shell-like (conchoidal) fracture pattern when broken. It is extremely common globally in sedimentary outcrops.