sedimentary
Chert (Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)
- Hardness
- 6
- Color
- reddish-brown
- Luster
- waxy to dull
Identified More sedimentary →
Explore Chert (Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)
Formation & geological history
Formed from the accumulation of silica-rich microfossils or via chemical precipitation within sedimentary rock layers, often associated with iron oxide impurities which give it the dark brown color.
Uses & applications
Historical use for stone tools/arrowheads due to its sharp edges; modern use as gemstones, landscaping rock, and in jewelry (lapidary).
Geological facts
Chert is so durable that it is often found in riverbeds long after the surrounding rock has weathered away. It was a primary material used by prehistoric humans for creating flint tools.
Field identification & locations
Identify by its hardness (will scratch glass) and its smooth, curved conchoidal fractures. Common in limestone formations and gravel deposits worldwide.
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