technical report on the nechalacho deposit, thor lake project ...

A high R 2 (and all regressions had significant p-values) for the regression, coupled with a high
p-value in the t-test reinforces the significance of the correlation between the Niton instrument
and the laboratory results.
A high R 2 coupled with a low p score on the t tests indicates that there is poor numerical
correlation between the Niton instrument and the laboratory results, but a good fit on a
regression line, implying that the variation in the Niton reading is proportional to the laboratory
estimate but there is a systematic percent bias in the Niton readings (either high or low).
Note that handheld XRF units can suffer precision, bias or general inaccuracies when
measuring extremes of contents – either very high or very low levels of an element.
Avalon concluded that Niton XRF analysis has been demonstrated to reflect laboratory analyses
for the elements Y, Ce, Ne, Sm and Gd. Furthermore, with more effort in instrument calibration,
acceptable results can be achievable for Ta and Zr. These conclusions are significant in that
the relative amounts of light and heavy rare earths are reasonably represented by
measurements of Ce and Y. Thus, the total rare earth grade and light rare earth (LREE)
content can be estimated using the Ce values and the relative proportion of heavy rare earths
(HREE) can be estimated using the Y grade. This can be supported in the case of LREE by the
Nd values and in the case of HREE by the Gd values.
NITON HANDHELD ANALYZER FOR GRADE AND QUALITY
CONTROL
Given the test results summarized above for using the Niton handheld analyzer on drill core, its
use in mining grade control and metallurgical monitoring can be discussed.
As noted above, at Nechalacho the rare earth mineralization, with the exception of zircon, is
invisible to the naked eye. Thus, underground grade control will be dependent upon chemical
analysis. It is suggested that this may be achieved for underground grade control purposes by
use of the handheld XRF analyzer. Use of such an instrument may enable the geologist to
outline stopes on the basis of grade and also be able to recognize instantly HREE-rich and
HREE-poor sections of the mineralization.
Analysis of rare metals such as rare earths, niobium, tantalum and zirconium is more complex
than base metals. As a result, routine analysis during mining operations could be slower and
more expensive than for base metals. Instant XRF analysis may be an efficient answer for this
issue. The handheld XRF analyzers are limited in power output, and hence sensitivity and
accuracy, due to safety concerns. An alternative is use of larger equipment that utilizes the
same principles, but higher power output. An example is the InnovX X-50 Mobile XRF. This
50kV instrument has a 200 µA beam meaning that short assay times and better detection limits
Technical Report 43-101 – March 13, 2011 Page 11-7
Prepared by Avalon Rare Metals Inc.