A novel process is proposed for the extraction of aluminum from clay, by which the aluminum is recovered as poly(aluminum chloride) solution requiring energy much less than that for the recovery as alumina, and the volume of the siliceous residue left after the aluminum was extracted from the clay can be reduced by 70% by extracting the silicon from the residue as sodium silicate solution. The poly(aluminum chloride) solution was made by partially decomposing the aluminum chloride hexahydrate, an intermediate product leading to alumina on complete decomposition, and subsequently dissolving the resultant basic chloride in water at 90 degrees C. About 80% of the silicon in the siliceous residue could be recovered as sodium silicate by leaching the residue with 20 wt % NaOH for 1 h at 100 degrees C under atmospheric pressure. The maximum molar ratio of SiO2:Na2O of the sodium silicate solution thus obtained was 3.0:1.