On the Mechanism of Formation of Fayalite (Experimental Study on the Reaction Between Wustite and Silica (2))

Two sets of experimental work were carried out to study the mechanism of fayalite formation.(1) A fayalite pellet was sandwiched between a wustite and a vitreous silica rod. And a platinum wire as a marker was placed at the interface of wustite and fayalite. Thus arranged specimen was heated at 1150°C for 24 hrs in an argon. The marker was moved into the fayalite pellet and sinter pores in the fayalite were also moved to and accumulated at the interface of fayalite and silica. The vitreous silica was crystallized due probably to a mineralizing action of wustite transferred into the silica. According to an electron-probe micro analyis it was considered that the iron in silica was mainly located in the boundary of the silica crystals.(2) Wustite powder and silica gel were mixed at the composition of fayalite and heated at 1000°C in vacuum for 10 to 600 min. The amount of fayalite formed and of wustite remained were determined by X-ray powder method. The rates of the formation of fayalite and of the reduction of wustite obeyed completely the parabolic rate low. The actual amount of the fayalite formed, however, was always lesser than that of the value calculated from the amount of wustite remained. This discrepancy seemed to be due to the presence of wustite acting as a mineralizer in silica.The mechanisms of the mineralizing action of wustite and the formation of fayalite were dicussed.