Published online by Cambridge University Press: 10 January 2013
The results of an international project involving five countries and seven laboratories performing over 400 analyses for testing the interlaboratory reproducibility and accuracy using quantitative powder diffraction are presented in this report. Four natural and four artificial mineral mixtures were examined. The RIR (reference intensity ratio) values for all mineral components were either measured or calculated. The relative standard deviation of the interlaboratory determinations range from 5 to 20 percent (for low concentrations, the relative standard deviations can attain 60% percent). Due to systematic errors, the relative standard deviations of the interlaboratory determinations generally exceed the standard deviations determined by individual laboratories. The best results were obtained when the RIR values were measured independendy in each laboratory.