Bargate stone is a highly durable form of sandstone. It owes its yellow, butter or honey colouring to a high iron content. In some contexts it may be considered to be a form of ironstone. However, in the context of stone buildings local to the extraction of Bargate Stone, the term 'ironstone' is often used to refer to a darker stone, also extracted from the Greensand, which rusts to a brown colour.

The Greensand Ridge, also known as the Wealden Greensand, is an extensive, prominent, often wooded, mixed greensand/sandstone escarpment in south-east England. Forming part of the Weald, a former dense forest in Sussex, Surrey and Kent, it runs to and from the East Sussex coast, wrapping around the High Weald and Low Weald. It reaches its highest elevation, 294 metres (965 ft), at Leith Hill in Surrey—the second highest point in south-east England, while another hill in its range, Blackdown, is the highest point in Sussex at 280 metres (919 ft). The eastern end of the ridge forms the northern boundary of Romney Marsh.