The Preparation and Evaluation of Bastnäsite Reference Materials IGS 40 and 41

Two bastnäsites ‐ rare‐earth fluocarbonate ores ‐ from Mountain Pass, California, each weighing 40 kg, were ground to ‐200 mesh (75 μm), homogenized, sub‐sampled into 432 containers and issued to interested laboratories for analysis in 1979. The methods used for the determination of rare‐earth oxides, are discussed and the analytical results have been evaluated statistically. Rare‐earth analysis remains a difficult field and, in the two samples, only nine elements have been assigned recommended concentrations. Appendices list the participating laboratories, the main determinations and information on the determination of other elements and oxides.