Alloying of copper with zinc or tin to make brass or bronze was practiced soon after the discovery of copper itself. One copper mine at Great Orme in North Wales, extended to a depth of 70 meters. At Alderley Edge in Cheshire, carbon dates have established mining at around 2280 to 1890 BC (at 95% probability). The earliest identified metalworking site (Sigwells, Somerset) is much later, dated by Globular Urn style pottery to approximately the 12th century BC. The identifiable sherds from over 500 mould fragments included a perfect fit of the hilt of a sword in the Wilburton style held in Somerset County Museum.