sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Hardness: 7 Mohs scale; Color: Dark brown to tan/grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 Mohs scale
- Color
- Dark brown to tan/grey
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Jasper/Flint variety) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs scale; Color: Dark brown to tan/grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids, replacing original carbonate material in sedimentary beds.
Uses & applications
Historically used for stone tools (arrowheads). Currently used for lapidary work, jewelry (when colorful like Jasper), and as a durable construction aggregate.
Geological facts
Chert breaks with a conchoidal fracture, creating sharp edges which made it the primary material for prehistoric survival tools and weapons.
Field identification & locations
Identify by its extreme hardness (scratches glass), waxy feel, and smooth curved break surfaces. Commonly found as nodules in limestone or as layer-cake beds in maritime sedimentary sequences.
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