sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Gray with yellow-orange limonitic staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Gray with yellow-orange limonitic staining
- 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: Gray with yellow-orange limonitic staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or groundwater environments. This pebble shows significant river or beach abrasion, rounding its edges over thousands of years.
Uses & applications
Historically used for making stone tools (arrowheads). Modern uses include landscaping, as decorative river stones, and occasionally as lapidary material for jewelry if the patterns are unique.
Geological facts
Chert is so durable that it often survives long after the surrounding rock has weathered away. The orange-yellow bands in this specimen are caused by iron oxide impurities that seeped into the micro-fissures of the stone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, rounded 'river stone' texture. Commonly found in riverbeds, glacial tills, and along coastlines.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary