sedimentary
Chert (specifically Flint or Jasper variant)
Microcrystalline silica (SiO2)
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 More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary