A composition comprising synthetic mineral particles, such as silicate or phyllosilicate mineral particles, is presented. The composition can be prepared by a process in which a hydrogel precursor of the synthetic mineral particles is produced by a coprecipitation reaction between at least one compound comprising silicon, such as sodium metasilicate, and at least one compound comprising at least one metal element, such as a dicarboxylate salt of the formula M(R1—COO)2, wherein R1 is H or an alkyl group having 1 to 4 carbon atoms. The coprecipitation reaction also takes place in the presence of at least one carboxylate salt of formula R2—COOM′ wherein M′ is Na or K, and R2 is H or an alkyl group having 1 to 4 carbon atoms.