Fig. 15

a SEM microscopic examination and micro structure of the outer facing granite blocks of Mykerinos pyramid. Micrographs show heavy materials disintegration and few trace elements are slightly immobile, whereas most major (particularly Ca and Na) and trace elements are mobile from the beginning of the granite weathering. On the other hand, there were mineralogical changes initiated from a plagioclase breakdown, which shows a characteristic circular dissolved pattern caused by a preferential leaching of Ca cation along grain boundaries and zoning. The biotite in that region is also supposed to be sensitive to exterior environmental condition. b EDX spectrum of the previous image of the grains of the facing granite blocks of Mykerinos pyramid. A strong silica, aluminum and potassium signals are observed. c SEM microscopic examination and micro structure of the facing granite blocks of Mykerinos pyramid. It seems that some rock-forming minerals in the granitic facing blocks are significantly unstable due to the environmental condition. d EDX spectrum of the previous image of granite grains of the facing granite blocks of Mykerinos pyramid. A strong silica signal is observed