sedimentary
Chert (often called Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with reddish staining; Luster: Waxy to dull; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and grey with reddish 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: Tan, brown, and grey with reddish staining; Luster: Waxy to dull; Crystal structure: Trigonal (cryptocrystalline); 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 in marine or groundwater environments. This specimen appears as a nodule or thick bed fragment.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to its sharp edges; used today as a road aggregate, in jewelry (as jasper), and for fire-starting (flint).
Geological facts
Chert was one of the first materials traded globally by early humans. It is so hard that it can scratch glass and steel. It often contains micro-fossils only visible under a microscope.
Field identification & locations
Identified in the field by its smooth, shell-like (conchoidal) fracture surfaces and its extreme hardness. Look for it in limestone layers or as rounded river cobbles.
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