sedimentary
Chert (Flint) with Patina
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan, gray, and cream with concentric banding, Luster: waxy to dull, Crystal Structure: cryptocrystalline, Fracture: conchoidal
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, gray, and cream with concentric banding, Luster: waxy to dull, Crystal Structure: cryptocrystalline, Fracture: conchoidal
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms (diatoms, radiolarians) or chemical precipitation in sedimentary basins, later modified by burial and localized weathering which creates the colored rings (liesegang rings or patina).
Uses & applications
Historically used for tools and fire-starting; currently used for decorative purposes, landscape gravel, and specimen collecting.
Geological facts
This specimen displays significant weathering rinds or concentric silica precipitation. The location (near Eisenstadt, Austria) is part of the Vienna Basin and the Alpine foreland, rich in sedimentary deposits where chert is common.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, waxy feel. It often breaks with very sharp, shell-like edges (conchoidal fracture). Common in gravel deposits and limestone outcrops in Central Europe.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary