Pyramid Stone Seams Fit Tighter Than a Piece of Paper

Using a copper chisel? That's a tool more expensive than iron. The outer stones of the Egyptian pyramids, 4,500 years ago, had seams just 0.5 millimeters wide, about the thickness of a razor blade. But iron didn't even exist back then. When they tried to scrape the stone with soft copper tools, the stone remained intact while the tool itself got blunted. So, the builders sprinkled sand beneath their saws. It wasn't the saw cutting the stone, but the hard grains of sand. Cutting was solved, but fitting two multi-ton stones together without any gaps was another problem. Ultimately, they flipped the concept: they placed two stones directly against each other and ground them down. As the protruding parts wore away, they naturally formed a perfect match. Finally, a slurry of gypsum acted as a lubricant, filling even the remaining tiny gaps. This is how seams as tight as a razor blade, where not even a piece of paper could fit, were created.