chert
/tʃəːt
/noun [mass noun]
A hard, dark, opaque rock composed of silica (chalcedony) with an amorphous or microscopically fine-grained texture. It occurs as nodules (flint) or, less often, in massive beds.The sedimentary lenses are composed of limestone, sandstone, siltstone, mudstone, shale, chert and well-bedded calci-turbidite....
- It comprises turbiditic elastic rocks with cherts, pillow lavas and greenstones.
- In fact, seventeen of the fifty-seven sites are specifically listed for agate, chalcedony, chert, jasper, or petrified wood.
Derivatives
cherty
- Nevertheless, many tectonic ironstones are rather massive, cherty rocks, suggesting that early structural fabrics were annihilated by late-stage chert replacement.
- These fracture zones occur as parallel layers alternating with cherty lithons, typically 5 mm wide, giving the rock a banded appearance.
- The cherty carbonate rocks are resistant to weathering, and regions underlain by them may stand above the surrounding terrain.
Origin
Late 17th century (originally dialect): of unknown origin.