sedimentary
Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, brown, or grayish; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Tan, brown, or grayish
- Luster
- Dull to waxy
Identified More sedimentary →
Explore Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, brown, or grayish; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed via the accumulation of siliceous remains of organisms or precipitation from silica-rich fluids within sedimentary basins; often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads); currently used in road construction, as an abrasive, and occasionally for lapidary work.
Geological facts
Chert is essentially the same mineral as flint, but the name flint is usually reserved for dark varieties found in chalk. It is highly resistant to chemical weathering.
Field identification & locations
Identified by its extreme hardness (scratches glass) and its smooth, shell-like (conchoidal) fracture pattern. Commonly found in riverbeds and gravel pits.
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