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

Semi-quantitative X-ray diffraction (XRD) analyses determined that the Nechalacho samples
tested were predominantly comprised of silicates with minor to moderate amounts of
oxides/hydroxides. Albite, microcline and quartz were identified as the dominant silicate
minerals, while magnetite and hematite were identified as the dominant oxide minerals.
Moderate to trace amounts of carbonate minerals were also documented.
Due to the sample matrix and high levels of rare earth elements (REE), semi-quantitative XRD
analyses could not be completed on the concentrates. Qualitative XRD results for the
concentrate samples did, however, indicate that the concentrates were also comprised
predominately of silicates and oxides. The Qemscan results demonstrate that 56% of the
concentrate sample comprises rare earth minerals and zircon, 31% of the sample is silicates,
almost 9% carbonates and only 0.7% sulphides.
Leach tests were performed on the ore, concentrate, tailings and waste rock. Shake flask
extraction leachates showed that waste rock was alkaline, while acid base accounting tests
showed that the ore and concentrate were potentially acid neutralising, with generally low
sulphur and higher carbonate neutralising potential. Most tests <strong>report</strong>ed pH values and other
parameters within World Bank limits with the exception of total suspended solids in the fresh
tailings solution.
Settling tests on the tailings samples concluded that the suspended solids would settle out of
the slurry fairly quickly. In the lab, solids settled out of the slurry in two to two and a half hours,
reaching terminal density shortly thereafter. Tests also concluded that drainage would improve
the rate of settling of solids.
The radionuclide analysis of the Nechalacho solids typically <strong>report</strong>ed increased levels of
radionuclides in the concentrate samples in comparison to the ore composites, while tailings
<strong>report</strong>ed lower levels than the ore samples.
Regulations governing radioactivity include:
• Transportation of Dangerous Goods Regulations (TDGR), with limit of 70 Bq/g;
• Health Canada Regulations on Naturally Occurring Radioactive Material (NORM);
• Northwest Territories Mine Health and Safety Act and Regulations which require control
on worker exposures where radon decay product levels exceed 0.4 WLM/y (Working
Level Months per year); and
• Canadian Nuclear Safety Commission if uranium and/or thorium materials are produced.
Thor Lake has uranium levels that are higher than average naturally occurring granite but are
below levels typically experienced in other rare earth deposits. The thorium levels in the
Nechalacho deposit are anomalous, but given the lower radioactivity equivalency of thorium
Technical Report 43-101 – March 13, 2011 Page 18-99
Prepared by Avalon Rare Metals Inc.