AbstractPart I showed that significant differences exist between calcium carbonate and silicate minerals when incorporated into polypropylene (three grades). It showed further that an ultrafine calcium carbonate, when coated with stearic acid, gives significantly better impact properties to the composite than a coated ground whiting but with no significant effect on its tensile properties. This article examines the effect of particle size and surface coating of chalk‐based calcium carbonate on the physical properties of GWE 21 Propathene homopolymer. The effect of variation in filler level was also investigate