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NIFF-ITASCA: <br /> Denver, Inc. <br /> As described above, samples containing carbonate minerals have the highest measured ANP <br /> values.The samples B2, B3, B5, and B7 were selected for Phase II testing because of the presence <br /> of carbonate minerals in these samples in combination with the representativeness of their NNP <br /> values relative to the overall population distribution. Comparison of the behaviors of these <br /> samples in HCTs with those of the samples that do not contain carbonate minerals facilitates <br /> further evaluation of potential acid-neutralization by carbonate minerals versus silicate minerals. <br /> The proposed Phase II testing of these samples enables further evaluation of the potential acid- <br /> neutralizing capacity of these carbonate minerals. <br /> Samples L2 and PC3 were selected to ensure the lamprophyre and Precambrian-biotite <br /> schist/gneiss rock-type groups were represented in the Phase II testing.Sample PC3 was classified <br /> as a mixture of generic Precambrian and biotite schist/gneiss rock type-groups. PC3 had an NNP <br /> value that is near the average for the entire sample group and is the only combined Precambrian- <br /> biotite schist/gneiss sample selected for Phase II testing. The lamprophyre and Precambrian- <br /> biotite schist/gneiss rock-type groups each represent less than 5% of the mined materials. <br /> The final sample selected for further analysis is PP6, which is porphyritic phonolite. This sample <br /> has the lowest measured NNP value of the samples selected for further analysis. PP6 is also of <br /> interest because it contains three groups of minerals: 1) potentially acid-neutralizing silicate <br /> minerals (potassium feldspar, plagioclase, illite/muscovite), 2) acid-generating minerals (pyrite <br /> and the acid-sulfate mineral jarosite), and 3) nonreactive minerals that do not contribute to ANP <br /> or AGP (quartz, rutile). This sample was anticipated to effectively test the ability of silicate <br /> minerals to neutralize the acidity generated by pyrite under environmental conditions. <br /> 9 <br />