sedimentary

Chert (specifically Flint or Jasper variant)

Microcrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Grey, blue-grey, with reddish-pink tones; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 7 on Mohs scale
Color: Grey, blue-grey, with reddish-pink tones
Luster: Waxy to dull

Identified April 11, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, blue-grey, with reddish-pink tones; Luster: Waxy to dull; Structure: Cryptocrystalline; 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 from groundwater within limestone or chalk beds. Most specimens date from the Phanerozoic eon.

Uses & applications

Used historically for stone tools (knapping) and fire-starting. Currently used as an abrasive, in road construction, and as decorative gravel or gemstone cabochons.

Geological facts

Chert was one of the most vital materials for early humans due to its ability to break with razor-sharp edges. It is chemically identical to quartz but has a different microscopic crystal structure.

Field identification & locations

Identify by its 'shell-like' (conchoidal) fracture patterns and ability to scratch glass. Commonly found in nodules within limestone or as river-worn cobbles. Search near sedimentary basins or stream beds.