sedimentary
Flint / Chert
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Grey, black, or brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 6
- Color
- Grey, black, or brown
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Flint / Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Grey, black, or brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed as nodules in sedimentary rocks like chalk and limestone through the replacement of calcium carbonate by silica-rich fluids. Often contains microscopic fossil remains.
Uses & applications
Historically used for stone tools and starting fires; currently used in grinding media, road construction, and as a decorative stone.
Geological facts
Flint was the primary material for the Stone Age technology due to its ability to break into sharp edges. It produces sparks when struck against steel.
Field identification & locations
Look for a glassy or waxy interior and sharp, shell-like (conchoidal) fractures when broken. Commonly found in coastal chalk cliffs or gravel deposits.
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