sedimentary
Chert (Banded)
Chert (Microcrystalline Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, beige with banding, Luster: waxy to dull, Crystal structure: cryptocrystalline, Fracture: conchoidal, Specific Gravity: 2.6
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, beige with banding, Luster: waxy to dull, Crystal structure: cryptocrystalline, Fracture: conchoidal, Specific Gravity: 2.6
Formation & geological history
Formed from the precipitation of silica-rich fluids or the accumulation of siliceous biological remains (like diatoms or radiolaria) in sedimentary layers. It can form as nodules or bedded layers in carbonate rocks.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; currently used as road aggregate, architectural stone, and occasionally in jewelry as semi-precious stones (jaspers/agates).
Geological facts
Chert was one of the first materials utilized by early humans to create fire and sharp tools. It is extremely resistant to chemical weathering, often outlasting the host rock it formed within.
Field identification & locations
Identify in the field by its superior hardness (scratches glass), waxy feel, and smooth curved (conchoidal) fractures. Found globally in limestone and dolomite formations.
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