Geopolymers

The apparently supremely carefully fitted ancient many sided blocks found around the world defy explanation, for example those at Cusco and Sacsaywaman.

Recent research suggests that the stone blocks at Puma Punku might be geopolymers, and cast in their complex shapes, not cut. Maybe the Sacsaywaman walls are also made of geopolymers.

Geoploymers can be almost indistinguishable from natural stone of which they are made, due to the very fine particle size and the chemical reactions when the blocks are made. More research is needed.

But if they are geopolymers, the implication is that the civilisation that made them could grind large volumes of natural stone into very fine powders. That takes a lot of energy, and a grinding device that is harder than the stone that will withstand the grinding process. It is just about possible to imagine large numbers of humans providing the energy over a long period of time, but much easier to imagine a metal machine driven by some energy source.

Which of course raises the same questions as the fine and incredibly accurate maching of hard rock that is visible in Egypt.