Carrstone (or carstone, also known as Silsoe, heathstone, ironstone or gingerbread) is a sedimentary sandstone conglomerate formed during the Cretaceous period. It varies in colour from light to dark rusty ginger. Used as a building stone it can be found in Bedfordshire, Cambridgeshire and extensively in the historic buildings of northwest Norfolk. Due to easy access to river transport, Carrstone can occasionally be found outside this region in such places as Great Bentley Church, Colchester, Essex.