This invention is directed to hydrodemetallization catalysts and hydrodemetallization processes employing a magnesium aluminosilicate clay. The magnesium aluminosilicate clay has a characteristic 29Si NMR spectrum. The magnesium aluminosilicate clay is the product of a series of specific reaction steps. Briefly, the magnesium aluminosilicate clay employed in the catalyst and process of the invention is made by combining a silicon component, an aluminum component, and a magnesium component, under aqueous conditions and at an acidic pH, to form a first reaction mixture and subsequently the pH of the first reaction mixture is adjusted to greater than about 7.5 to form a second reaction mixture. The second reaction mixture is allowed to react under conditions sufficient to form the magnesium aluminosilicate clay. The resulting magnesium aluminosilicate clay combines high surface area and activity for use in hydrodemetallization catalysts and processes.