sedimentary
Chert (White Chert / Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Pure white to off-white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Pure white to off-white
- 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 on Mohs scale; Color: Pure white to off-white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or sponge spicules) or by the replacement of carbonate minerals in limestone/chalk. Found in sedimentary layers of various ages.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; used today as road surfacing, in ceramics, and as a component in concrete.
Geological facts
Because it breaks with a conchoidal fracture (smooth, curved surfaces), it was the primary material for prehistoric humans to craft weapons. It is chemically very stable and resistant to weathering.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and curved, glass-like fracture surfaces. Often found as nodules within limestone or chalk beds.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary