sedimentary
Chert / Flint
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Gray to dull brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline) quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Gray to dull brown
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert / Flint in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Gray to dull brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline) quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed as nodules or layered deposits in sedimentary rocks (typically limestone or chalk) through the accumulation of silica-rich organic remains or chemical precipitation from groundwater.
Uses & applications
Historically used for stone tools and starting fires; currently used as construction aggregate, road base, and occasionally in lapidary work.
Geological facts
Flint is a variety of chert that was essential to prehistoric humans for making arrowheads and axes due to its ability to break into sharp edges through conchoidal fracturing.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, shell-like (conchoidal) breaks. Found globally in sedimentary basins.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary