sedimentary
Chert (Jasper/Flint variety)
Microcrystalline quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Mustard yellow to brown (ochre); Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Mustard yellow to brown (ochre)
- Luster
- Dull to waxy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Mustard yellow to brown (ochre); Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of siliceous remains of organisms or chemical precipitation from silica-rich fluids in sedimentary basins. Primarily Paleozoic to Cenozoic eras.
Uses & applications
Historically used for stone tools (knapping). Currently used as landscaping stone, road aggregate, and sometimes as a minor gemstone (Jasper) in jewelry.
Geological facts
Chert is so hard it can scratch steel and was once the primary material for making arrowheads and spear points due to its sharp conchoidal fracture edges.
Field identification & locations
Identify by its 'shell-like' curved (conchoidal) fractures and its ability to scratch glass. Commonly found in riverbeds, glacial till, or as nodules within limestone/chalk layers.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary