sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Brown, tan, and reddish-grey; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Cleavage: None.
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, and reddish-grey
- Luster
- Dull to waxy
Identified More sedimentary →
Explore Chert (Jasper/Flint variety) 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: Brown, tan, and reddish-grey; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Cleavage: None.
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in sedimentary basins. Most common in Paleozoic and Mesozoic strata.
Uses & applications
Historically used for stone tools and weapons (arrowheads) due to its sharp edges when fractured. Currently used in road construction, as decorative landscaping stone, and occasionally in lapidary work.
Geological facts
Chert is so hard it can scratch steel and produce sparks when struck against iron, which is why flint (a variety of chert) was essential for early firearms and fire-starting.
Field identification & locations
Identify by its extreme hardness, waxy texture on fresh breaks, and curved (conchoidal) fracture patterns. Frequently found as nodules in limestone or chalk beds.
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