1994-02-28_REVISION - M1988112 (2)

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Duncan and Bruynesteyn (1979), respectively. The Net Acid Production Test (Coastech Research Inc., 1989) was modified to use a stronger peroxide so ution and to incorpn~ate recent advancements by O'Shay et al. (1990). To a 1.00 g mine waste sample (80% minus 200 mesh) 100 mL of hydrogen peroxide (at least 30~ v/v with distilled) was added incrementally (since the reaction of hydrogen peroxide and sulphide can be violent), and the mixture was heated to near boiling for one hour. If the peroxide was depleted after one hour, 50 mL of peroxide was added and heated for 30 minutes. The flask was cooled for ]0 to 15 minutes and 1 mL of 0.0157 M copper solution was added and the mixture was boiled for 10 minutes. The solids were removed by filtration and washed with 1 M CaClz. A sample of the filtrate was then titrated to pH 7.0. Four samples were analyzed for sulphur before and after the NAP test (RK- 4, TL-1, TL-3, TL-6). RESULTS AND DISCUSSION Chemical and mineralogical analyses indicated the samples displayed fair degree of compositional diversity. The sulphur content of the ten mine waste samples ranged from 0.46 to 5.81 percent, and from 88 to 99 percent of the sulphur was present as sulphide (Table 1). Pyrite was the predominant iron sulphide in all samples except RK-2, TL-3, and TL-6, in which pyrrhotite dominated. The calcium carbonate and magnesium carbonate mineral content of the samples ranged from trace amounts to a maximum of 4.6 percent. Siderite was also present in measurable amounts in four of the samples (Table 2). Quartz, feldspar, and mica were the major host rock minerals in all samples except TL-6. The NAP Test was evaluated based on 1) qualitative comparison of predictions by the NAP Test with those by the standard ABA, Modified ABA, and B. C. Research Initial Tests on whether or not a mines waste sample would produce acidic drainage, 2) quantitative comparison of Net NP values determined by the NAP Test with those determined by the other three static tests and the Net NP determined based on sample composition, and 3) qualitative comparison of Net NP values with mineralogical analyses of the samples tested. Static test prediction of whether or not a mine waste will produce acidic drainage can be based on the Net NP determined by the test. Steffen, Robertson and Kirsten (B.C.) Inc. et al. (1989) indicated that "based on general experience, values of Net NP in the range !(between) -20 and +20 tonnes of CaCOl/1000 t of sample (-2 to +2% CaCO,) may be considered to have the ability to generate net acidity." It was further noted by Ferguson (1989) that there was poor agreement among static tests on the acid generating character of samples with Net NP values in this range. To simplify data presentation, Net NP values in this range will be referred to as inconclusive. Values below -20 kg CaCO,/t imply the sample is acid producing, while values 148