sedimentary
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, brown, tan, or black; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, brown, tan, or black
- 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, brown, tan, or black; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of siliceous remains of marine organisms (like diatoms or radiolaria) or via chemical precipitation from silica-rich fluids in limestone or chalk beds. Often found in nodules or bedded layers.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used as road aggregate, in jewelry (when decorative like jasper), and as a spark-maker in survival fire-starting kits.
Geological facts
Chert has a conchoidal fracture, allowing it to break into razor-sharp edges. It was one of the most vital materials for early human technological development.
Field identification & locations
Identify in the field by its waxy texture and shell-like (conchoidal) curved breaks. It will easily scratch glass and produce sparks when struck against steel. Commonly found in limestone outcrops or riverbeds.
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