The invention relates to a collection of composite plateletlike particles comprising a core and at least one coating layer consisting essentially of a compound having from 60 to 95% by weight of carbon and from 5 to 25% by weight of nitrogen, the balance to 100% being selected from elements of the group consisting of hydrogen, oxygen and sulfur. The invention also relates to processes for the manufacture thereof, to polymer compositions containing it, and to the use thereof as effect pigments. Preferably, the process for preparing the instant collection of particles comprises the steps of (a) suspending plateletlike particles in a liquid; (b) optionally adding a surface modifier, a polymerisation catalyst or both; (c) before or after step (b), adding one or more polymers containing nitrogen and carbon atoms, or one or more monomers which are capable to polymerize to said polymer; (d) effecting a polymeric coating layer to be formed on the surface of said plateletlike particles from the polymers or monomers added at step (c); (e) isolating said plateletlike particles having said polymeric coating layer from the suspension; and (f) heating said plateletlike particles having said polymeric coating layer to a temperature of from 100° C. to 1000° C. in a gaseous environment.