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Show iHOW ORES ARE" ENRfGHEOFOR USE Nature's Processes Described In Re-! Re-! port By United States Geo logical Survey As originally deposited, deep In the rocks, many of tho familiar metals, especially copper, lead, zinc stiver and quicksilver exist as sulphides that Is ns minerals composed of ono or more metals chemically combined with sulphur. sul-phur. In such original or primary de posits tho generally worthless Iron sulphide, pyrltc,, Is likely to predominate, predom-inate, whllo tho more valuable metal mhy bo present In quantities too small to bo profitably extracted. In tho course of geologic ages, how-over, how-over, ns tho land wears down under tho ceaseless attack of weather and running wnter, tho primary ore deposit, de-posit, with Its small proportion of valuable metals, Is itself exposed to tho forces of disintegration nnd decnv thnt nro operating over all land surfaces sur-faces on tho globe. Some constltu cnts of tho disintegrating oro ore car rled nwny In streams; somo nro blown nwny by winds; and others, partlcu Inrly some of the metal, nro dlssolv ed nnd carried by percolating rain water down Into the earth. These metal charged solutions, coming Into contact with the sulphldo minerals In tho rocks, havo tho chemical property proper-ty of transforming these sulphides In to others moro valuable to man. Thus solutions carrying copper hnd coming Into contact with pyrlto which Is a mineral compound of sulphur nnd Iron, nbstract some of the Iron and leave copper in its placo. The bright yellow, beautiful hut generally useless use-less pyrlto may bo changed, for ex-amplo, ex-amplo, to tho less brilliant dark gray but far more valuablo mineral clinl-coclte, clinl-coclte, n sulphldo of copper. This nntural chemical concentration, where by ob tho exposed upper portion of an oro body decays and Is removed by erosion, Its valunblo constituents nro In lorgo part carried down and added to tho portion that remains. Is nn exceptionally important process nnd ono thnt has played an esscntlil part in tho formation of many lnrg1 and highly productive bodies or oro Investigations By American Geologists IOrowing recognition of tho overwhelming over-whelming Importhnco of enrlchmen' ' .n the formation of some of tho largest larg-est copper deposits of tho world dato from tho year 1900 and Is duo chiefly chief-ly to tho work of American geologists. A recent publication of tho United States Geological Survey (Bulletin 529) entitled "Tho Enrichment of Sulphldo Ores," by W. H. Emmons, Is devoted to tho description and discussion dis-cussion of this process. Tho volume, which Is Intended to bring together nil tho information at present available avail-able on downward sulphldo enrichment, enrich-ment, is divislblo Into two parts. Tho first part deals with the various conditions, such as cllmato and porosity por-osity of tho rocks, that influence tho process nnd with tho physical and chemical principles Involved. Tho second se-cond part reviews briefly tho available avail-able knowledge of North American mining districts In so far as this knowledgo bears on tho problems of enrichment. Tho chemistry of enrichment en-richment is very fully discussed In connection with the various minerals miner-als found In ore deposits and tho students of oro deposition will find tho book Invaluable as a summary of what Is known on the particular subject treated and as a guldo to tho llternturo that relates to It. Valuable Report Can Be Had Free Tho present publication, like Clarke's "Data of Geochemistry," Bulletin 491 of tho U. S. Geological Survey Illustrates tho effort now bo-Ing bo-Ing made by the survey to bring together, to-gether, for convenient reference by busy men, data now scattered not only through its own reports but In other publications also. Such volumes, vol-umes, however, aro not mere compilations. compila-tions. The previously published material ma-terial Is enriched by new observations and is illuminated by discussion in tho light of the latest scientific knowledgo. "The Enrichment of Sulphldo Ores," Bulletin C29, may bo obtained free on application to the Director United States Geological Survey, Washington D. C. The demand f i tho second edition of "Tho Data of Geochemistry" has been so great it was reprinted last yew, and the reprint has recently becomo exhausted. exhaust-ed. Another edition will bo issued by tho survey during tho present year. |
