sedimentary
Chert (River Pebble)
Cryptocrystalline Quartz (SiO2)
Hardness: 7 Mohs; Color: Tan to brown; Luster: Waxy to dull; Crystal structure: Trigonal; Cleavage: Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Tan to brown
- 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 Mohs; Color: Tan to brown; Luster: Waxy to dull; Crystal structure: Trigonal; Cleavage: Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich microfossils or chemical precipitation in marine or freshwater environments. This specimen was likely smoothed by fluvial action (river transport).
Uses & applications
Historically used for stone tools/flintknapping; currently used in decorative landscaping, as road base, or for polishing in rock tumblers.
Geological facts
Chert and flint are essentially the same material; the name 'flint' is usually reserved for dark varieties found in chalk beds. It is one of the most durable sedimentary rocks.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, rounded water-worn texture. Commonly found in riverbeds and gravel pits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary