sedimentary

Chert (often called Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Hardness: 7 on Mohs scale
Color: Tan, yellow-brown, or mustard
Luster: Waxy to dull

Identified April 5, 2026More sedimentary →

Explore Chert (often called Flint or Jasper) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within sedimentary layers like limestone or chalk.

Uses & applications

Historically used for stone tools due to its sharp edges when fractured; modernly used in road construction, as decorative gravel, or for lapidary work.

Geological facts

Chert was one of the most important minerals to prehistoric humans for crafting arrowheads and spear tips because of its predictable conchoidal fracture pattern.

Field identification & locations

Identify in the field by its hardness (it will scratch glass and steel) and its waxy surface texture. This small specimen appears to be a water-worn river pebble, found commonly in gravel pits or stream beds.