sedimentary
Chert (Field Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or white with a weathered yellowish rind (cortex); Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 6
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Field Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or white with a weathered yellowish rind (cortex); Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often replacing limestone or chalk. Frequently found as nodules or beds in sedimentary layers.
Uses & applications
Historically used for stone tools and starting fires; currently used as road aggregate, architectural filler, and by flintknappers for decorative arrowhead replicas.
Geological facts
Chert is so hard it can scratch steel. It was one of the most vital materials for prehistoric humans because it breaks with incredibly sharp edges through conchoidal fracturing.
Field identification & locations
Identify in the field by its distinct waxy interior compared to a rough, chalky outer crust. It is commonly found in areas with limestone or chalk deposits globally. Use a scratch test; it will easily scratch glass.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary