sedimentary
Chert (Flint/Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: typically brown, gray, or tan; Luster: waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: none (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- typically brown, gray, or tan
- 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: typically brown, gray, or tan; Luster: waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: none (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms (diatoms, radiolarians) or by chemical precipitation from silica-rich fluids in sedimentary basins. Often found as nodules in limestone or chalk.
Uses & applications
Historically used for stone tools and starting fires (flint). Currently used in road surfacing, as grinding media, and occasionally in jewelry as lapidary material.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for arrowheads and scrapers.
Field identification & locations
Identify by its waxy appearance, extreme hardness (it will scratch glass), and its tendency to break with smooth, curved surfaces (conchoidal fracture). Common in areas with limestone bedrock.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary