Morphological features of the lime-enhanced hydrogen reduction of cuprous sulfide pellets were investigated as a function of temperature and time by scanning electron microscopy. Moderate temperatures of reduction (600-750[degrees]C) were found ti result in the formation of fibers and loops of copper, whereas at high temperatures of reduction (900-1000[degrees]C) only sintered crusts of spongy copper were obtained. The sequence of nucleation and growth of copper fibers was found to be the formation of pits and pores on the sulfide particles, followed by the nucleation of copper preferentially in these pores, the emergence of copper hairs from the sulfide base, and the formation and thickening of loopy fibers. These events are explained on the basis of the reduction characteristics and nonstoichiometry of cuprous sulfide and its mismatch with the product metal. While lime enhances the bulk reduction rate of cuprous sulfide, it does not seem to affect the mechanism of copper fiber formation.