sedimentary
Chert (specifically Jasper or Flint type)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs), Color: Tan to reddish-orange, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Identified More sedimentary →
Explore Chert (specifically Jasper or Flint type) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs), Color: Tan to reddish-orange, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed primarily through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from groundwater within sedimentary layers. This process can occur over millions of years, often in limestone or chalk beds.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp conchoidal fracture. Today used as an abrasive, in landscaping, and as a semi-precious gemstone in jewelry when it displays attractive colors (Jasper).
Geological facts
Chert has been used by humans for hundreds of thousands of years to create fire (by striking against steel) and edges sharper than a surgical scalpel. It is one of the most durable sedimentary rocks.
Field identification & locations
Identify by its smooth, waxy feel and the way it breaks into curved, shell-like flakes (conchoidal fracture). It cannot be scratched by a steel knife. Frequently found in stream beds or eroding out of limestone cliffs.
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
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 (primarily SiO2)
sedimentary