sedimentary
Chert (specifically Brown Chert or Flint)
Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Brown, tan, or liver-colored; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, or liver-colored
- 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: Brown, tan, or liver-colored; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within limestone or chalk beds. It can date from the Precambrian to the Cenozoic era.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a component in ceramics or glass-making. Polished specimens are used in jewelry and lapidary art.
Geological facts
Chert exhibits conchoidal fracture, meaning it breaks like glass to create razor-sharp edges. It was arguably the most important resource for prehistoric technological advancement.
Field identification & locations
Identify in the field by its smooth, waxy surface and curved, shell-like (conchoidal) fracture patterns when broken. It will scratch glass but cannot be scratched by a steel knife. Common in riverbeds and limestone outcrops.
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