The present invention provides a process for preparing a precipitated calcium carbonate product comprising the steps of: (a) preparing an aqueous suspension of precipitated calcium carbonate seeds by carbonating a suspension of Ca(OH)2 in the presence of 0.005 to 0.030 moles of Sr, in the form of Sr(OH)2, per mole of Ca(OH)2, (b) dewatering and dispersing the precipitated calcium carbonate seeds prepared in step (a) to obtain an aqueous suspension of precipitated calcium carbonate seeds having a d50 of less than or equal to 0.1 to 0.3 μm and a BET specific surface area of 10 to 30 m2/g, and (c) forming an aqueous suspension of a precipitated calcium carbonate product by carbonating a slurry of Ca(OH)2 in the presence of 0.5 to 5% by dry weight of the precipitated calcium carbonate seeds obtained in step (b), wherein the precipitated calcium carbonate seeds have a d50 that is less than the d50 of the precipitated calcium carbonate product and the precipitated calcium carbonate seeds have an aragonitic polymorph content greater than or equal to the precipitated calcium carbonate product obtained in step (c) characterized in that the dewatering of step (b) is carried out by the use of a tube press.