Abstract: The present invention provides synthetic, finely divided water-insoluble layered silicates having a smectite-like crystal phase, with increased contents of bound alkali and silicate and a distinctly reduced swelling power in aqueous suspension relative to pure layered silicates of this type. The synthetic layered silicate of this invention has the following oxide summation formulaMgO.aM.sub.2 O.bAl.sub.2 O.sub.3.cSiO.sub.2.nH.sub.2 Owherein M is selected from the group consisting of sodium and a mixture of sodium and lithium said mixture having a molar ratio of sodium to lithium of at least about 2,n represents the number of water molecules bound in the crystal phase, anda, b, c and n each represent a number having a value within the following ranges:a is from about 0.05 to about 0.4b is from 0 to about 0.3c is from about 1.2 to about 2.0, andn is from about 0.3 to about 3.0.