sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs, Color: reddish-brown/tan, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs, Color: reddish-brown/tan, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary beds. These specimens are often found as nodules or pebbles in stream beds or coastal deposits.
Uses & applications
Used historically for stone tools due to sharp fracture edges; currently used for decorative gravel, lapidary tumbling, and jewelry.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create arrowheads and scrapers. Red varieties are specifically known as Jasper.
Field identification & locations
Identify by its conchoidal (shell-like) fracture pattern and its ability to scratch glass. It is common in riverbeds and limestone formations worldwide.
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