sedimentary
Chert / Flint
Chert (Cryptocrystalline Quartz, SiO2)
Hardness: 7 (Mohs scale); Color: Brown, tan, cream; Luster: Waxy to dull; Structure: Cryptocrystalline (microscopic crystals); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Brown, tan, cream
- 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 (Mohs scale); Color: Brown, tan, cream; Luster: Waxy to dull; Structure: Cryptocrystalline (microscopic crystals); Cleavage: None (conchoidal fracture); Specific gravity: 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 (arrowheads, scrapers) due to its sharp edges; used in construction as road metal and aggregate; also used in fire-starting kits (flint).
Geological facts
Chert was one of the first materials used by early humans for tools because of its conchoidal fracture, which creates razor-sharp edges. It is incredibly durable and chemically resistant.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel), waxy texture, and conchoidal (shell-like) fracture patterns. Frequently found in stream beds or within 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