From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.