flintnod
Colour: Blue-grey, grey, to nearly black when fresh, but weather to a whitish, powdery crust (patina).

Texture: Very fine-grained and smooth; conchoidal fracture. Rough on weathered surfaces.

Structure: Flint and chert form rounded nodules of widely differing forms, but chert also forms massive beds. Flint nodules are often hollow and may contain a fossil, such as a sponge or echinoid.

Mineralogy : Composed of silica, mainly the variety chalcedony. Some authors distinguish flint and chert compositionally but the differences, if any, are slight.

Field relations: Flint and chert nodules occur typically in limestone and chalk. They are usually patchily distributed but often concentrated along one bedding plane. Their origins are not fully understood; but some appear to be secondary replacements of the host rock, whilst others may represent primary deposition on the sea bed of colloidal silica. ​(Hamilton et al 1976, 204)

patinated flint

patination

flint tool
scraper