sedimentary
Chert Nodules in Limestone
Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)
Hardness: 7 (chert) vs 3 (limestone); Color: Gray, brown, and reddish iron-staining; Luster: Waxy to dull; Breakage: Conchoidal fracture in the chert center.
- Hardness
- 7 (chert) vs 3 (limestone)
- Color
- Gray, brown, and reddish iron-staining
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert Nodules in Limestone in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (chert) vs 3 (limestone); Color: Gray, brown, and reddish iron-staining; Luster: Waxy to dull; Breakage: Conchoidal fracture in the chert center.
Formation & geological history
Formed via chemical precipitation where silica replaces carbonate material in marine environments. Often found in Paleozoic or Mesozoic era limestone beds.
Uses & applications
Chert was historically used for stone tools (arrowheads). Today it is used in construction aggregate and as a geological study specimen.
Geological facts
The reddish tint is likely due to iron oxide (hematite or limonite) staining. Chert nodules like this are often very resistant to weathering compared to the surrounding limestone.
Field identification & locations
Look for nodes or seams that are much harder than the host rock; it will scratch steel. Commonly found in limestone cliffs and quarries globally.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary