sedimentary

Chert (Tan or Buffer variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, beige, brown
Luster: Waxy to dull

Identified March 23, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (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 Paleozoic or Mesozoic in age.

Uses & applications

Historically used for stone tools and arrowheads due to sharp edges; currently used for road surfacing, as an abrasive, and by hobbyists for flint knapping.

Geological facts

Chert is so hard it can scratch steel and spark when struck against iron. 'Flint' is a variety of chert, typically used to describe dark gray or black specimens.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and inability to be scratched by a steel blade. Commonly found in nodular form within limestone outcrops globally.