sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan, reddish-brown, grey; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale), Color: tan, reddish-brown, grey
- Color
- tan, reddish-brown, grey
- Luster
- waxy to dull
Identified More sedimentary →
Explore Chert (Jasper/Flint variety) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: tan, reddish-brown, grey; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the precipitation of silica-rich fluids or the accumulation of silica-based microorganisms (like radiolarians) in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools/weapons due to its sharp edges. Modern uses include abrasive materials, road surfacing, and as a decorative stone/lapidary material if highly colorful.
Geological facts
Chert has been used by humans for millions of years to create arrowheads and scrapers. When struck against steel, it can produce sparks, leading to its historical use in flintlock firearms.
Field identification & locations
Identify in the field by its hardness (will scratch glass), smooth waxy feel, and conchoidal (shell-like) fracture patterns on broken surfaces. Often found in riverbeds or within sedimentary outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary