MA-lb is a sample of ore from the Macassa Mine at Kirkland Lake, Ontario. The major mineral constituents of the ore matrix are quartz, feldspar, and dolomite, with minor amounts of muscovite, chlorite and pyrite. Chalcopyrite, sphalerite, hematite, magnetite, altaite and melonite are present in minor to trace levels. Gold occurs mainly as native metal or electrum (alloy with minor silver constituent) mainly as inclusions in the siliceous matrix but also in pyrite. Calaverite (AuTe2) occurs as inclusions in some pyrite grains. The approximate chemical composition of MA-lb is given in the Table.
The ore was dry ground and sieved. The -74 µm fraction was blended and bottled in 200-g units. The stock was sampled systematically and analysed by fire assay/gravimetry (FA/G) and fire assay/ atomic absorption spectometry (FA/AAS) procedures to demonstrate sufficient homogeneity of gold for application as a compositional reference material.
The recommended value for gold is the unweighted mean of 175 accepted analytical determinations by 28 laboratories. The uncertainty is the estimate of the expected range of reproducibility of this mean with 95% probability, if the measurement program was to be repeated many times. This estimate assumes the results are a sampling from an ANOVA Model ll statistical model.
Results by method classifications are compiled in the Table, where FA refers to fire assay preconcentration, ICPAES refers to inductively coupled plasma atomic emission spectrometry, INAA refers to instrumental neutron activation analysis, and other symbols are described above. CI is the 95% confidence interval for the mean and SLc and Src the between- and within-set standard deviations obtained from the ANOVA. CV is the average within-set coefficient of variation. The median within-set replacation was 5 and the median sample weight was 15g.