Upon exposure to water and oxygen, these minerals oxidize to form acid-, iron- and sulfate-rich drainage.

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And in fact those same sulfate particles are a primary ingredient in acid rain, so loading the atmosphere with them is probably not a good idea either (although geoengineering proponents have suggested doing exactly that to help cool the climate).

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Mr. TOM McCOLLOM (Geochemist, University of Colorado): The sulfate salts that are in there come from reaction of the rock with sulfuric acid rather than from evaporation of a fluid.

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