This reminds me of a radio program I heard a few years ago which suggested that the Pyramids in Egypt were fashioned out of synthetic sandstone. The person being interviewed [I forget what program it was--it was one I'd never heard of as I was driving hundreds of miles out of range of my usual radio stations] said that she'd determined a means of making synthetic sandstone using only materials and technologies which would have been present in ancient Egypt. Transportation of huge blocks would have posed much less of a technical challenge if they were ground, then transported, and then reformed.
Sounds like Margaret Morris, coauthor of Joseph Davidovits' book on geopolymerization processes possibly used by various folks, particularly the ancient Egyptians, to synthesize stones of widely varying sizes and uses.
http://www.geopolymer.org/science_archaeology/index.html