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.