E/MJ : engineering and mining journal . picked sample) (5). These figures indicate anaverage silver content of a little over 5 02. per ton ol small silver content is nevertheless considerablygreater than the average of the Joplin, Mo., or south-west Wisconsin lead and zinc districts, which were withoutmuch doubt deposited by meteoric waters, and is morethan double that of the southeast Missouri disseminatedlead ores, which by most authorities at least are consid-ered to have been deposited by meteoric water-. The calamine and smithsonite derived From the sul-phide deposits have been
E/MJ : engineering and mining journal . picked sample) (5). These figures indicate anaverage silver content of a little over 5 02. per ton ol small silver content is nevertheless considerablygreater than the average of the Joplin, Mo., or south-west Wisconsin lead and zinc districts, which were withoutmuch doubt deposited by meteoric waters, and is morethan double that of the southeast Missouri disseminatedlead ores, which by most authorities at least are consid-ered to have been deposited by meteoric water-. The calamine and smithsonite derived From the sul-phide deposits have been frequently and excellently de-scribed. Oxidized ores were formed to some extent by the oxidation of these sulphides in place, but these secondary ores were to a larger extent repreeipitated aroundand particularly at the base of the limestone pinnaclesso characteristic an accompaniment of the oxidized part the oxidized ores replace the limestone alongfractures as both crystalline ami globular bodies, the softer Surface of Ground. Bed of Original Sulphides EnrichmentSecondarySulphides FIG. 3. SHOWING RELATION OF SECONDARY SULPHIDESAND CARBI (NATES and more sandy (decomposed) limestone being morereadily replaced than the hard unaltered of the zinc carbonate opencuts were originallyiron-ore pits, and recently some of the oxidized zincdeposits have been mined for limonite iron ore. As arule where iron ore predominates in the clay, the pinnaclesare well rounded ami loaf-shaped and composed of solidrock: where much zinc ore is present, however, the pin-nacles are remarkably uneven and jagged in form andthe limestone decomposed to a sand-like mass. Brec- ciation of the limeston sing the pinnacle- in zinc deposits is also much more common than inproducing predominantly iron ore. Secondary sulphide enrichment is common, althocommercially of no greal in portance, and in deposits inwhich original sulphides are not minable, the secondaryenriched sulphides will probabl
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
