Hot filament CVD method can be used to grow micron-sized diamond crystals in the quantity of several millions per square centimeter. These crystals are polyhedral with fully developed facets. Such uniform-shaped crystals can be sized easily with tight distribution. When they are used to polish workpiece, they may not cause conspicuous scratches. Moreover, the smooth surfaces Of these whole crystals can minimize the amount of adhered impurities, so that the contamination of workpiece may be avoided. The micro-diamond crystals so grown are the ideal superabrasive for polishing high-valued materials such as semiconductors and other electronic devices.