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Show DETERMINE VITAL MINING PROBLEM For the time being the chemical side of the question of secondary chalcocite in ore deposits- appears to be settled, says the Engineering and Mining Journal. The chemists of the geophysical laboratory of the Carnegie institution have taken a hand in the matter, and in their usual thorough manner have established the main facts as to the deposition of this mineral on other sulphides. The investigations investi-gations were quantitative throughout. The experiments with pyriie. cha Icopyrite, pyrrhotite, bornite, sphaiterite and galena show that the process always involves a formation of sulphate of the meUtls of the precipitating sulphides. ' All the reactions were studied at several sev-eral temperatures ranging from 200 degrees de-grees down to 30 degrees C. It was shown conclusively that at 50 degrees sulphides of copper (chalcocite or covel-lite) covel-lite) resulted from a reaction between pyrite crushed finer than C00 mesh and cupric sulphate. The solution lost 50 mg. of copper in six months and a corresponding cor-responding amount of iron sulphate and sulphuric acid was found in the solution. solu-tion. This solves definitely a mooted question ques-tion that long has occupied the attention atten-tion of mining geologists. In the same manner chahopyrite alters to covellite and chalcocite, while bornite and covellite alter to chalcocite alone. Sphaiterite and galena are easily converted first to covellite covel-lite and then to chalcocite. Many other important reactions have also been studied in this interesting investigation which throw light on secondary ores. |