sedimentary
Chert (Flint variety)
Microcrystalline or cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or grey
- 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, beige, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of silica-rich organic remains (like diatoms or radiolaria) in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; used today as road surfacing material and for decorative landscaping.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces razor-sharp edges. It is often referred to as 'Earth's first high-tech material.'
Field identification & locations
Look for a smooth, waxy surface and shell-like (conchoidal) fractures. It is harder than steel and will scratch glass. Commonly found in sedimentary basins and along 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