The Vessels Proof

One of Sakkara’s 30.000 stone vessels at the Cairo Museum.
Beneath the earth, below the base of the Sakkara Step Pyramid, Imhotep his builder and designer quarried out almost three miles of stone and built a series of corridors and inner chambers.
He decorated some of the chambers with blue enamel tiles, as far we know the first ever made by man; a proof of his advanced knowledge of alchemy.
In addition to all this, some thirty thousand stone vessels of the utmost perfection were found in these subterranean chambers. There are unique and enigmatic hard stone vessels, made of slate, diorite and basalt. Some of these materials are harder than iron. No sculptor today would even attempt to work with such material.
One wonders how could they have been carved? Their design is extremely beautiful and impossible to carve. No tool marks are found on their surfaces. They must have been cast in molds, in accordance with the indications suggested by the Irtysen Stele at the Louvre gallery.
The Le Chatelier Proof

Henri Le Chatelier.
The first man to posit a reasonable solution to how the Egyptians made their stone statues, was Henri Le Chatelier, a chemist, ceramist and metallurgist, born in France in 1850.
In the early twentieth century, he noticed that the famous statue of Pharaoh Khafra (or Khefren) revealed no sign of tool marks. Yet it had been made of diorite, the hardest type of stone, at a time when artisans possessed only simple stone or copper chisels. He concluded that with tools like these it would have been impossible to produce such a masterpiece.

Diorite statue of Pharaoh Khefren.
Le Chatelier suspected that it had not been carved at all, but made of agglomerated stone cast in molds, so he began to examine other statues. He looked at ones that were apparently enameled, and cut thin sections of them with a diamond-tipped saw, and found that the enamel was not an applied coating but part of the material from which the statue was made. He asserted that they were cast in some kind of synthetic material not sculpted in natural stone.