Abstract: Novel finely divided particulate calcium carbonate compositions comprising mixtures of a preponderance of dry ground calcium carbonate with a smaller amount of wet ground calcium carbonate, each of these components having particular particle size characteristics and particle size distributions, are disclosed. When used as all or part of the filler in thermosetting and thermoplastic resinous compositions, e.g., thermosetting polyester resinous molding compositions, paints and other finishes, sealants and the like, such mixtures provide compositions having high filler loadings coupled with acceptably low viscosities and better processability than resinous compositions containing all dry-ground fillers.