Sarsen stones are stone blocks found in quantity on Salisbury Plain, the Marlborough Downs, in Kent, and in smaller quantities in Berkshire, Oxfordshire, Dorset and Hampshire. They're the remains of a cap of tertiary sandstone which once covered much of southern England. It's a dense, hard rock created from sand bound by a silica cement, making it a kind of silicified sandstone. Natural sarsen boulders created by glacial and periglacial effects can be sometimes found scattered on the ground surf… (More on Sarsen)