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41 GEM SERVICES <br /> Dawson Project—Tailings Characterization Page 7 <br /> 3.1.2 Acid Generation Potential <br /> The potential of the development rock and tailings to generate net acidity was assessed using the <br /> modified Acid Base Accounting test. The laboratory reports are provided in Appendix B. A <br /> summary table of results is presented in Table 3. <br /> The paste pH is a measure of a sample's current acidity status. Rinse pH was also measured for <br /> the development rock samples to determine the current acidity status of the development rock <br /> surfaces. The paste pH for all samples ranged from 6.9 to 9.6, indicating all samples are neutral <br /> to slightly alkaline. Rinse pH for development rock ranged from 8.8 to 9.4. <br /> Sulfur is predominantly present as sulfide (its reduced form) or sulfate(its oxidized form). <br /> Sulfide is the sulfur species that once exposed to air and water will oxidize and produce acid. <br /> Sulfur speciation was completed on all samples to determine the sulfide content and is shown in <br /> Figure 2. While all samples contain sulfur, only one development rock sample (and its duplicate) <br /> contain sulfide sulfur above the detection limit of 0.01 wt%. <br /> 0.10 <br /> 0.09 <br /> 0.08 <br /> 0.07 • <br /> 0.06 <br /> g 0.05 <br /> 0 <br /> i✓ <br /> 0.04 • <br /> 0.03 • <br /> 0.02 • • <br /> 0.01 • <br /> 0.00 <br /> 0.00 0.01 0.02 0.03 0.04 <br /> Sulfide S <br /> •Tailings •Development Rork <br /> Figure 2: Total Sulfur vs. Sulfide Sulfur <br /> The neutralization potential determination by the modified Sobek method(used in this study)is <br /> the measurement of the ability of a known amount of pulverized sample to neutralize a known <br /> volume and strength of a strong acid over a short exposure period. This bulk neutralization <br /> potential will account for the neutralization contributed by both carbonate and aluminosilicate <br /> minerals. However,the speed of neutralization and the pH to which these minerals will <br /> neutralize is different. The most effective neutralization is from carbonate minerals,which react <br /> with acid rapidly and neutralize water to a circum-neutral pH. For this study, carbonate <br /> neutralization was measured by determining the amount of total inorganic carbon present in the <br /> samples. As discussed in Section 3.1.1 above, siderite was measured in the altered tailings <br /> DDSldds Zephyr DawsortTailings_Charactedzation_Final Report,Feb.3,22,1:1 B PM Feb 2022 <br />