A fireclay refractory ceramic can be made by heating the raw material kaolinite, $A{l}_2(S{i}_2{O}_5)(OH{)}_4,$ driving off the water of hydration.

A modest rearrangement of the kaolinite formula helps to clarify the production of this ceramic product.

$A{l}_2(S{i}_2{O}_5)(OH{)}_4=A{l}_2{O}_{3}2Si{O}_{2}2H_{2}O$

The firing operation yields

$A{l}_2{O}_{3}2Si{O}_{2}2H_{2}OA{l}_2{O}_{3}2Si{O}_2+2H_2$Ouarr

Upon cooling below the eutectic temperature shown in Figure $2,$determine the phases present in $A{l}_2{O}_{3}2Si{O}_2,$ their composition, and their amount for the resulting microstructure.