Joanne Bourne has been in awe of flint as long as she can remember. It was all around her where she grew up in Kent: used for garden walls, to edge drives and weight dustbin lids, as well as to build pubs, churches, Roman villas and castles. For centuries it was the only building stone available. It is also magical. Made from the remains of plankton and sea sponges, it is second only in hardness to a diamond and can be used to make fire. Part of human development for three million years, it was used as a weapon to hunt and in war, and hung as protection against thunderbolts and fairies. In a deeply personal love letter to this extraordinary 'biogenic' rock, Bourne traces its geological, architectural and social history and invites us to roam with her in search of it on her beloved North Downs. Fusing science, poetry, history and a profound love of landscape, this is her heartfelt, thoroughly persuasive tribute to the stone she calls 'an art project of the great divine'.