An ammonium carbonate leach solution containing dissolved nickel and/or cobalt values is sprayed into a flash chamber to flash a portion of the ammonia therefrom, resulting in the production of a fine precipitate of nickel and/or cobalt carbonate. The solution is introduced into a stripping tower wherein remaining ammonia is stripped therefrom to precipitate further nickel and/or cobalt carbonate on the previously precipitated carbonate, which function as nuclei to reduce deposition in the column.