sedimentary

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with possible banding; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Tan, brown, and grey with possible banding
Luster: Dull to waxy

Identified March 26, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with possible banding; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (knapping); modernly used for road aggregate, landscaping, and occasionally lapidary work or semi-precious jewelry.

Geological facts

Chert is so hard it can strike sparks against steel, making it a primary material for 'flint and steel' fire starting and early firearms (flintlocks).

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and inability to be scratched by a steel blade. Commonly found in limestone or chalk beds and along riverbanks/beaches.