sedimentary
Chert (specifically Flint or Jasper variant)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: tan, brown, and translucent cream; Luster: waxy to vitreous; Crystal structure: Trigonal (microscopic fibers); Cleavage: None (showcases conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- tan, brown, and translucent cream
- Luster
- waxy to vitreous
Identified More sedimentary →
Explore Chert (specifically Flint or Jasper variant) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: tan, brown, and translucent cream; Luster: waxy to vitreous; Crystal structure: Trigonal (microscopic fibers); Cleavage: None (showcases conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the chemical precipitation of silica in groundwater. It often replaces carbonate minerals in limestone or chalk beds.
Uses & applications
Historically used for stone tools (knapping arrows and scrapers) and starting fires. Modernly used as a decorative stone, in jewelry (as Jasper or Agate), and as an abrasive in some industrial applications.
Geological facts
Chert was one of the most vital materials for prehistoric humans because of its ability to fracture into extremely sharp, glass-like edges. It is chemically very stable and resistant to weathering.
Field identification & locations
Identify in the field by its waxy texture, extreme hardness (it will scratch glass), and the shell-like (conchoidal) curves on broken surfaces. Often found as nodules in limestone or as seafloor bedded deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary