An analytical methodology was developed for the quantification of niobium. tantalum. iron and manganese in samples of ores and solid residues coming from ore pressure leaching, using different acids. The adopted instrumental technique was X-ray fluorescence on pelleted solid samples. Comparison of the analytical data obtained by application of this method to ore and leaching residue samples with those obtained by a reference method showed that the experimental results were statistically acceptable. (C) 2002 Elsevier Science Ltd. All rights reserved.