sedimentary
Chert (Jasper variation)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Brownish-red with white quartz veining; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brownish-red with white quartz veining
- Luster
- Waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-red with white quartz veining; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich microfossils like radiolaria or diatoms on the ocean floor, subsequently compacted and hardened. It can also form through chemical precipitation from silica-rich fluids.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to its sharp edges. Modernly used for landscaping, tumbled stones, and semi-precious jewelry (as Jasper).
Geological facts
Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, leading to its historical use in flintlock firearms.
Field identification & locations
Identify by its smooth, waxy surface and shell-like (conchoidal) fractures. Often found in riverbeds or as nodules within limestone or chalk formations.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary