It has been found that hard attrition-resistant zeolite X molecular sieve bodies can be produced by admixing zeolite X powder and meta-kaolin clay followed by the hydrothermal conversion of the meta-kaolin clay to zeolite X. When a reaction mixture contains from about 70 percent to 90 percent by weight of zeolite X powder and from about 10 percent to 30 percent by weight of meta-kaolin clay, this admixture will hydrothermally convert to essentially all zeolite X material. This conversion is accomplished without the addition of any silica source other than the silica provided by the meta-kaolin clay.