Flint often forms as nodules in sedimentary rocks such as chalk and marine limestones. The nodules can be dispersed randomly throughout the rock unit but are often concentrated in distinct layers. It has been used by humans to make stone tools for at least two million years. The conchoidal fracture of flint causes it to break into sharp-edged pieces. Early people recognized this property of flint and learned how to fashion it into knife blades, spear points, arrowheads, axes, and other sharp tools using a method known as flint-knapping. It is very common in Norfolk, and many buildings are faced with it. This small piece of flint was picked up in the area of Grime's Graves.

See more about Grime's Graves here: en.wikipedia.org/wiki/Grime%27s_Graves