CompuServe Messages

Elizabeth: Re: self-combusting sulfides. Grain-size certainly is a factor, w/ increased surface area available for reaction in finer materials, etc. I recall anecdotes that Kuroko-type massive sulfides in Japan have problems w/ "self-igniting" ores on occasion. On a field trip to Homestake's McLaughlin mine in CA, we observed a "smoking face" on one of their benches one damp afternoon. The material was fine-grained pyrite & stibnite and actually hot to the touch. (The "smoke" was mostly steam from evaporating rainwater.) Sulfide oxidation rxns tend to be strongly exothermic – in certain sulfide smelters, the feedstock actually doubles as "fuel". Perhaps Gilchrist's (1989; Permagon Press) "Extraction Metallurgy" can give you some leads – my shelf of ore geology books is rather silent on pyrophoric phenomena. Good luck! Cheers, Scott M.