A method of manufacture of zinc monoglycerolate containing an incorporated modifier, and the product, the zinc monoglycerolate being in the form of agglomerates of crystallites, wherein the crystallite size based on the average coherence domain length is not more than 30 nm in the direction, and not more than 60 nm in the direction, as determined by the Scherrer equation via powder X-ray diffraction; and the aspect ratio computed by / coherent domain lengths is less than 0.65, preferably less than 0.56, in particular less than 0.44. Polymers containing this nucleating agent and methods for their production are also described. The zinc monoglycerolate is useful as a nucleating agent, and is very effective at low loading levels in polymers such as polypropylene.