sedimentary
Chert (Iron-stained)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Rusty brown, tan, or grey due to iron impurities; Luster: Dull to waxy; Structure: Microcrystalline with conchoidal (shell-like) fracture; Cleavage: None.
- Hardness
- 7 on Mohs scale
- Color
- Rusty brown, tan, or grey due to iron impurities
- Luster
- Dull to waxy
Identified More sedimentary →
Explore Chert (Iron-stained) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Rusty brown, tan, or grey due to iron impurities; Luster: Dull to waxy; Structure: Microcrystalline with conchoidal (shell-like) fracture; Cleavage: None.
Formation & geological history
Formed from the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds.
Uses & applications
Historically used for making stone tools (arrowheads). Modernly used as construction aggregate, road base, and occasionally for rock tumbling/landscaping.
Geological facts
Chert is extremely durable and chemically resistant. When it contains high amounts of iron oxide, it takes on the characteristic brownish-red 'jasper-like' appearance seen in this specimen.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, curved fracture surfaces. Commonly found in riverbeds, gravel pits, and glacial till.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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 (primarily SiO2)
sedimentary