The engineers' goal is to avoided trouble and unnecessary work. They wouldn't have ground up hard stone. They used soft limestone species (at that time) which could easily be grounded up without special tools. The hard species of limestone was avoided. Later when they lost the recipe or resources for geopolymer, they used complete blocks and those may have been the known reports about ship transport of large blocks.

It's simple: If you see the 3-5% geopolymer binder in the stone, it's geopolymer You need to place a small sample under an SEM (scanning electron microscope) to check for crystal or amorphos structure and EDS (energy dispersive x-ray spectroscopy) to view those element quantity spectrum graphs he often shows in this presentations.

It would be interesting to know of those handheld x-ray spectrometers like [www.bruker.com] could also help here already without the need of taking a sample, but I'm not sure if that's sufficient as with the SEM/EDS combination you can pinpoint the scanner beam at microscopic feature precisely.