In Egypt, the return of agglomerated (geopolymer) stone
1300 years after the Great Pyramids,
under Amenhotep III and Akhenaton (18th Dynasty).
Divine incarnation in carved stone became the rule under the New Kingdom around 1400-1200 B.C. and the hegemony of the god Amun. The soft sandstone from the Silsilis quarries, used for in the great temples at Karnak and Luxor, is so easy to carve that everything appears simple. So why should there be any controversy about the monuments and objects dating from this period? Because some are made out of an extreme hard material: quartzite!
It is true that 1300 years after the great pyramids, agglomerated stone, geopolymer stone was again being used, albeit sporadically, under the domination of Amun. After all these years, the worship of the god Khnum and initiation into his mysterious technology had not been forgotten. The greatest Egyptian scientist-architect-scribe, Amenophis Son of Hapu (1437-1356 B.C.), eminence grise of the pharaoh Amenhotep III, XVIIIth Dynasty, re-introduced it and used his alchemical (geopolymer) knowledge to build amazing statues made out of quartzite with geosynthesis and geopolymerisation. And the heretical king Akhenaton, son of Amenhotep III, did the same in order to rival the supremacy of Amun by forbidding carved granite stone.
The Colosses of Memnon, with Joseph Davidovits in the foreground (1979).
The clues for geosynthesis (geopolymerization), artificial quartzite stone
Geologists fail to agree between themselves in determining the origin of the quartzite stone used to the famous colosses. To summarise, French and German archaeologists/geologists claim that the Colosses of Memnon were sculpted in a quarry 70 km further south down the Nile and that they were brought up by boat. Other British and American researchers propose an even more extraordinary exploit. According to them, the statues were carved, then transported upstream on the Nile from a place 700 km downstream near to Cairo. Each team of scientists uses more and more sophisticated methods in pursuing their research, including atomic absorption, x-ray fluorescence and neutron activation. When applied to the most enigmatic of Egyptian monuments, these new techniques shed more confusion than light.