sedimentary
Chert (Jasper/Chalcedony pebble)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, reddish. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal (shell-like) fracture.
- Hardness
- 6
- Color
- Brown, tan, reddish
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Jasper/Chalcedony pebble) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, reddish. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal (shell-like) fracture.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by chemical precipitation in marine or groundwater environments. These pebbles are often rounded by water erosion in riverbeds or coastal areas.
Uses & applications
Used historically for stone tools due to its sharp edges; today used as decorative gravel, in lapidary work (tumbling), and as a minor gemstone (jasper).
Geological facts
Chert has been used by humans for millions of years to create arrowheads and scrapers. Because it is harder than steel, it can produce sparks when struck against iron, making it a primitive fire-starter.
Field identification & locations
Identify by its 'waxy' texture and the way it breaks into smooth, curved surfaces. Common in riverbeds and gravel pits globally. It will easily scratch glass.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary