"[T]he pyramid blocks are not natural stone; the blocks are actually exceptionally high-quality concrete—synthetic stone—cast directly in place. The blocks consist of... ninety to ninety-five percent limestone rubble and five to ten percent cement. ...imitations of natural limestone, made in the age-old tradition of alchemical stonemaking. No stone cutting or heavy hauling was ever required..."
January 1, 1970
https://en.wikiquote.org/wiki/Joseph_Davidovits