Name: | Flint or Chert |
Derivation: | From "flint" (Danish) Chert's derivation is unknown |
Description: | Opaque, grey, brown or black, sometimes with a chalky outside. Flint should only be used for the black variety. The rest is chert. |
These specimens are natural. The one on the right shows a conchoidal fracture. Flint doesn't break into smooth cleavage planes. Instead it fractures. A conchoidal fracture has curved lines, rather like a sea-shell (which is where the word "conchoidal" comes from).