sedimentary
Chert (varieties: Flint or Jasper)
Silicon dioxide (SiO2) / Microcrystalline Quartz
Hardness: 7 on Mohs scale; Color: Tan, brown, white with dark interior; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, white with dark interior
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (varieties: Flint or Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, white with dark interior; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.
Formation & geological history
Formed by the precipitation of silica in sedimentary environments, often from the remains of siliceous organisms like diatoms or radiolarians. Commonly found as nodules in limestone or chalk beds.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges; current uses include road surfacing, decorative landscaping, and as a component in glass manufacturing.
Geological facts
Chert has a conchoidal fracture, allowing it to break into sharp curved edges. This property made it the primary material for prehistoric survival tools and weapons for millions of years.
Field identification & locations
Look for a waxy texture and shell-like (conchoidal) fracture patterns when broken. It is harder than steel and will scratch glass. Found globally, especially in limestone-rich regions.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary