A novel magnetic abrasive particle (MAP) was developed by using electroless nickel or nickel-diamond composite plating on active carbon (AC) powder. The chelating compound of picolinic acid with nickel anion was used in the activated process instead of the conventional PdCl2 and SnCl2. X-ray diffraction and scanning electron microscopy images showed the completely coated nickel or nickel-diamond electroless deposits on the AC particles. A mirror finish of Cu plate was obtained by using the newly developed MAP in practice in the process of magnetic-field-assisted finishing. (c) 2005 The Electrochemical Society.