cement, making it a kind of silicified sandstone. Human uses The builders of Stonehenge used these stones for the heelstone and sarsen circle uprights. Avebury and many other megalithic monuments in southern England are also built with sarsen stones. Fire or explosives were sometimes employed to break the stone into pieces of a suitable size for use in construction. Sarsen isn't an ideal building material, however. William Stukeley wrote that sarsen is "always moist and dewy in winter which pro… (More on Sarsen)