Ancient Saw Cuts?

On our Megalithic Marvels of Egypt tour, we began exploring around the outside of the Great Pyramid of Giza where ancient tool cut marks can be found on various megalithic blocks such as this one. This stone is made of very hard basalt. Upon close examination, there appear to be at least 10 vertical cuts at the base. This clearly could not have been done with copper chisels and hammers, so what ancient tool made this? More evidence of a lost technology?