News Releases

December 2006

Onera's know-how in the service of Egyptology

Materials physicists have analyzed the microstructures of stones coming from the Egyptian pyramids and proved that they are not natural but "synthetic".

The facing of this pyramid (upper part) is made of reconstituted stone. Several theories have been elaborated to explain the mystery of the building of the great pyramids of Egypt . Thus for 30 years Joseph Davidovits, a chemist at the Geopolymer Institute in St-Quentin and Egyptologist, has been defending the thesis that the calcareous blocks, particularly those of the facing, were reconstituted and cast on the spot, like concrete.

Though observation of the blocks of stone in place and their arrangement strongly supported presumptions in favor of this theory, which was highly contested elsewhere, it lacked any real scientific proof.

Gilles Hug, a researcher at Onera, and Michel Barsoum, a materials specialist at Drexel University in Philadelphia , undertook investigations in the manner of scientific policemen, aimed at getting stones to talk, the ones that were presumed to be artificial.

They examined samples using various methods, normally used at Onera for understanding the transformation mechanisms of metals and optimizing their properties: plasma torch, X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM respectively). The "observations", resulting from spectrometry and electron or photon diffraction, provided knowledge of the basic compositions and identified the crystalline microstructures and amorphous aggregates.

They found amorphous magnesium silicate, observed by TEM. This compound is not expected in sedimentary rock but may result from a "geopolymer" type chemical reaction.

It seems that the proportions of elements found are not those of stones from the quarries exploited and above all that the crystals and aggregates present do not exist in the natural state in the sedimentary rocks. Conclusion: the samples are not of sedimentary but synthetic stone. And necessarily, the Egyptians had mastered the specific chemistry of geopolymer cement, whose components (ash, natron salts, lime, limestone, gypsum...) were available near the building sites...

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