Stone Type: Flint
Flint occurs as nodules or seams in chalk. It is a folk classification within the general category of chert. Chert nodules form when tiny organisms extract pure silica from ocean water and use it as body armour or skeletons. When the organisms die, their skeletons dissolve and form a siliceous ooze, which eventually precipitates, coalesces, and recrystallises as the surrounding limestone rock is formed. When the material precipitates into hollows such as crustacean or mollusc burrows, nodules are formed. Fine-grained varieties of chert are some of the best stones for flintknapping because of the exceptionally high silica content.
The term ‘flint’ is often used interchangeably with chert in popular descriptions of stone tool-making. To further complicate the use of the term, some geologists use ‘flint’ to classify any dark grey to black chert, regardless of whether it derives from chalk deposits. Further, many European-trained archaeologists distinguish chert from flint based on quality, with ‘flint’ referring to the most siliceous variants and more grainy (and usually light-coloured) variants referred to as ‘chert’. Flint that occurs as nodules in chalk is coloured dark or medium grey, black, brown, reddish-brown, or off-white grey.