sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Smoky grey to tan, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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: Smoky grey to tan, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Forms primarily through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or by chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Today used in road construction, stone age replicas, and occasionally as a fire starter when struck against steel.
Geological facts
Flint is a variety of chert that occurs in chalk or marly limestone. When it breaks, it creates exceptionally sharp edges, which led to its widespread use by early humans during the Stone Age.
Field identification & locations
Identify in the field by its waxy texture and sharp, shell-like (conchoidal) edges when broken. It will scratch glass easily. Commonly found in riverbeds or eroding out of limestone cliffs.
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
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary