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0 2.04.6 <br />• <br />SULFUR FORMS D -2 SEAM <br />Sulfur Forms ( %) <br />Drill Hole <br />Pyritic <br />Organic <br />Sulfate <br />Total <br />DH -12 <br />0.01 <br />0.35 <br />0.00 <br />0.36 <br />DH -22A <br />0.02 <br />0.38 <br />0.00 <br />0.40 <br />DH -8A <br />0.05 <br />0.39 <br />0.00 <br />0.44 <br />Reference: Reclaiming mine soils and overburden in the western United <br />States, by R. Dean Williams and Gerald E. Schuman, Editors, for the <br />following discussion regarding acid forming material in the D -2 Seam coal. <br />Iron pyrite is an acid forming material. The reaction of the pyritic sulfur is: <br />2FeS2 + 7202 + 71-12 - - -> 2Fe(OH)3 + 2H2SO4 <br />Or, commonly stated, Iron Pyrite in the presence of oxygen and water will be <br />oxidized to Ferric Hydroxide and Sulfuric Acid. This reaction may be either <br />chemical as described above or microbial. Several species of bacteria gain <br />energy from the oxidation of Iron Pyrite to form the above reaction products. <br />In oxidizing conditions at pH > 4.0, ferric oxide will form. At pH < 4.0 under <br />oxidizing conditions, a mineral called jarosite will form. Jarosite is very <br />insoluble and is not a concern. A common iron mineral, goethite, will form in <br />small amounts across the common pH spectrum under slightly oxidizing <br />conditions. <br />If the acid produced under complete oxidation is not buffered by the <br />surrounding mineral matrix, about 625 pounds of Calcium Carbonate (lime, <br />CaCO3) would be required to neutralize 1,000 tons of material bearing 0.01 % <br />iron pyrite such as in DH -12. <br />PR -12 2.04-21- 02/10 <br />