Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
th
, 2014
10135-200-46 – Rev. 0
11-11
11.6.5 Relative Standard Deviation
The percent RSD (Relative Standard Deviation = Standard Deviation divided by the
mean) values are displayed in Table 11.2. RSD is a measure of a standard’s
performance. One normally expects a well-behaved standard to have an RSD value
of less than 5%. Provisional standard RSD values range from 5-15%. Materials with
RSDs of less than 15% are acceptable for use as certified reference materials.
Materials with RSD’s of greater than 15% (highlighted by the red font in Table 11.2)
are not normally used or certified as reference materials.
In the original round robin studies the standards were certified for Y, La, Ce, Pr, Nd,
and Sm analyses. RSD values in Table 11.2 show that the standard history analyses
have acceptable accuracy and precision for analyses of Y, La, Ce, Pr, Nd, Sm, Eu
and Gd. The analytical history indicates that the standards are not as effective for the
heavier rare earth elements (Tb, Dy, Ho, Er, Tm, Yb, and Lu), because of the difficulty
that both Actlabs and ALS have in producing consistently reliable analyses for
samples with low concentrations of heavy rare earth element from year to year as the
instrumental calibrations change. This should not have a significant impact upon
resource calculations, as the total heavy rare earth element oxide percentage of the
combined heavy (Gd through Lu) oxides amounts to less than 1-2% of the total rare
earth oxide content of the samples. One can see this in Table 11.2, where the RSD
values for the %TREO are all acceptable with values of less than 4.5.
The RSDs for %TREO for each individual laboratory are elevated by the year-to-year
calibration changes, which have an impact on the analytical results, but should have
no significant impact on resource calculations owing to the low concentrations of
these elements.
