sedimentary
Chert (Jasper/Flint variation)
Chert (SiO2)
Hardness: 7 (Mohs), Color: Dark brown or grayish with lighter bands, Luster: Waxy to vitreous (especially when tumbled), Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs), Color: Dark brown or grayish with lighter bands, Luster: Waxy to vitreous (especially when tumbled), Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules within limestone or as bedded deposits. Ages vary from Precambrian to Cenozoic.
Uses & applications
Historical use for sharp tools/arrowheads. Modern use as decorative landscaping stones, road gravel, and tumbled stones for rock collectors.
Geological facts
Chert is so hard it can create sparks when struck against steel. It was one of the most important minerals for early human survival for making fire and hunting tools.
Field identification & locations
Identify by its waxy texture, high hardness (will scratch glass), and rounded 'river-stone' appearance if eroded. Commonly found in riverbeds and limestone outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary