2014-12-29_REPORT - M1977215 - Laserfiche WebLink

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Mr. Randy McClure/Rio Grande Silver, Inc. 10 MLI Job No. 3819 -November 26, 2014 HC kinetic ARD potential test data are summarized below. BDP-F 1391-051113 • Extract pH was fairly neutral and stable. Extract pH ranged from pH 4.52 (week 11) to pH 6.16 (week 24). • Redox potential was oxidizing and ranged from 179 (week 14) to 368 (week 18)mV. This range of oxidizing potential is typical of solid/solution systems exposed to air,but was never at the oxidizing level (>450 mV) to indicate oxidation of sulfide minerals. • Conductivity values were low and generally decreasing during the test, and ranged from 161 (week 23)to 761 (week 0) gS/cm. • Iron mobility(dissolution)was moderate and fairly stable over the last five weeks of testing. • Sulfate mobility was moderate. Sulfate concentration decreased gradually after week 0 and were stable for the last ten plus weeks of testing. Of the maximum available sulfate contained in the solids, 30.61 percent was mobilized during the kinetic test. • Acidity was detected in all weekly extracts and concentrations ranged from 8 (week 3)to 25 (week 21) mgCaCO3 equivalents/L. Maximum available acidity was 1,600 mg/kg and 182.18 mgCaCO3/kg was consumed (11.39% of total) during the HCT. • Alkalinity was detected in all weekly extracts and concentrations ranged from 1 (multiple weeks)to 5 (weeks 20 and 24)mgCaCO3 equivalents/L. Maximum available alkalinity was 2,000 mg/kg,but only 27.38 mgCaCO3/kg was consumed (1.37% of total) during the HCT. • Metals mobility was fairly low and stable. BDP-TBWTC-HC • Extract pH was basic(alkaline) and stable. Extract pH ranged from pH 7.36 (week 1)to pH 8.86 (week 7). • Redox potential was oxidizing and ranged from 293 (week 2)to 361 (week 12)mV. This range of oxidizing potential is typical of solid/solution systems exposed to air,but was never at the oxidizing level (>450 mV) to indicate oxidation of sulfide minerals. • Conductivity values were low and fairly constant during the kinetic test, and ranged from 61.5 (week 11) to 426 (week 0) µS/cm. • Iron mobility(dissolution) was slight. • Sulfate mobility was slight and decreasing during the test. Of the maximum available sulfate contained in the solids, 20.23 percent has mobilized during the kinetic test. • Acidity was not detected in any weekly extract. • Alkalinity was detected in all weekly extracts and concentrations ranged from 22 (weeks 5 and 11)to 37 (week 13)mgCaCO3 equivalents/L. Maximum available alkalinity was 6,300 mg/kg,but only 231.55 mgCaCO3/kg has been consumed(3.68% of total) during the HCT. • Metals mobility was low and stable. Table 10 provides maximum available acidity, sulfate and alkalinity in the tested samples, on a mass basis, and those component dissolutions (mass basis) during the HC kinetic ARD potential test. Maximum availability data obtained from Mod ABA static ARD potential testing results. McCLELLAND LABORATORIES, INC.