The writer Sara Maitland conjures with a rock of ages, Lewisian gneiss. Two-thirds the age of the earth itself, and the oldest stone in the UK, it makes up parts of the Northwest Highlands and the Western Isles. It's part of this week's series of Cornerstones - nature writing about rock, place and landscape.

Sara reflects on how the gneiss began its slow journey across the face of the earth more or less where Antarctica is today. It is still moving northwards, at about the same speed as our nails grow. 'Gneiss' comes from the German word meaning to sparkle, and Sara wonders whether it's this quality that convinced Neolithic builders to construct the Callanish stone circle on Lewis from this distinctive, ancient stone.

The other Cornerstones essays broadcast on Radio 3 this week hears different writers reflecting on how other rocks shape landscapes and us, such as flint, North Sea oil and gas, gypsum, which is the main constituent of plaster, and the clay bricks that define our urban landscapes.

Producer: Mark Smalley

Image: Courtesy of the artist Rose Ferraby