sentences:  Eighty percent of the ancient quarry sites are in the Nile valley; some of them have disappeared under the waters of Lake Nasser and some others were lost due to modern mining activity.Some of the sites are well identified and the chemical composition of their stones is also well known, allowing the geographical origin of most of the monuments to be traced using petrographic techniques, including neutron activation analysis.In June 2006 the Supreme Council of Antiquities (SCA) of Egypt established a new department for conservation of ancient quarries and mines in Egypt.