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9/30/93 <br />Responses to Comments <br />San Luis Reclamation Evaluation Report <br />Page 24 <br />Cumulative Fe reports in micrograms whereas cumulative sulfate <br />reports in milligrams, and the sulfate concentrations are <br />nearly 1000 times greater than the iron. Apparently, there is <br />a source of sulfate other than FeSs. As I am not aware of the <br />presence of sulfates such as anhydrite or gypsum in the ore <br />body. I have assumed that the sulfate which reports in the <br />humidity cell tests is from weathering of sulfides. if this is <br />so, there are sulfides other than Fe. I do not see the source <br />in the other leachate analyses. <br />What is the source of sulfate in the Humidity Cell Tests? <br />Response: The primary source of the sulfate reporting in the <br />humidity cell tests is the addition of sulfur <br />dioxide as part of the INCO detoxification system, <br />the addition of zinc ferrous sulfate as pact of the <br />CYTOX detoxification, and the addition of sulfuric <br />acid as part of the AVR detoxification system. As <br />noted throughout the report, the detoxification <br />processes resulted in soluble sulfate in the <br />tailings which either remains in the pore water or <br />precipitates, primarily as gypsum, to the tailings <br />solids phase. <br />