The Colossi of Memnon Revisited: Recent research has established the source of the stone of the two 720-ton statues at Thebes.

The only areas that are likely to have furnished the original stone for the Colossi of Memnon are near Cairo (Gebel el Ahmar), Aswan, and possibly Silsileh. Neutron activation analysis of samples from the colossi shows them to be distinctly different from samples obtained from the three known quarries near Aswan and from the quarries near Silsileh and Edfu, but very similar to samples obtained from Gebel el Ahmar. Petrographic analysis of colossi and quarry samples also provides strong evidence that the colossi came from Gebel el Ahmar. The blocks used by the engineers of Septimius Severus to reconstruct the north colossus were shown by neutron activation analysis to have originated from a deposit other than Gebel el Ahmar. The composition of these blocks conformed with samples taken from the quarries 8 and 9 km north of Edfu (the quartzite deposit closest to Thebes) and from the Aswan quarries. Petrographic analysis associated these reconstruction blocks with Edfu but not with Aswan. Neutron activation analysis of other artifacts in the area of the colossi indicates that they also came from Cairo rather than Aswan.