Horsham Stone is a type of calcareous, flaggy sandstone containing millions of minute sand grains and occurring naturally in the Weald Clay of south-east England.[1] It is also high in mica and quartz. The rock extends in an arc-like formation for several kilometres around the town of Horsham from which it takes its name, and lies just below the Weald Clay surface in bands 10 to 13 centimetres (3.9 to 5.1 in) thick.[1] Horsham Stone is significant for its ripple-marked appearance, formed by the action of the sea similar to the ripples on the sandbanks and beaches of Sussex.[2]