Abstract: Synthetic magnesium aluminosilicate consisting essentially by weight of 47-57% SiO.sub.2, 9-11% Al.sub.2 O.sub.3, 3-5% MgO, 1-3% CaO, and less than 5% Na.sub.2 O, balance water to total 100% calculated analytically.A process for manufacturing, comprising the steps ofstirring into a first aqueous solution, containing the corresponding amounts of magnesium sulfate and aluminum sulfate, a second aqueous solution containing sodium silicate and sodium hydroxide.thereafter adding a third aqueous solution containing a corresponding amount of calcium chloride,continuing the stirring,filtering off and washing the precipitate, anddrying the precipitate at a temperature below 100.degree. C.,or, instead of adding the third aqueous solution containing calcium chloride, by using lime water in the manufacturing process and for washing.