Carbonates are a very rare and volumetrically insignificant family of igneous rocks composed mainly of carbonate minerals, and normally are described in terms of their habits (intrusive) and composition (mineralogy). No other association of igneous rocks exhibit as great a diversity of rock types and intrusive habit. They vary in shape and size with depth … Read more
The Grasberg copper-gold orebody is contained with a young igneous complex of dioritic composition which intrudes limestones of the Tertiary New Guinea Group. Alteration is typical of porphyry copper deposits worldwide except that higher grade primary chalcopyrite with significant gold values is associated with a centrally located zone of strong quartz stockwork. The Grasberg … Read more
Kennecott Corporation, in joint venture with Galactic Resources Ltd., recently began operation of an open pit gold mining and milling facility near Columbia, South Carolina. The deposit consists of two ore bodies (North and South deposits) hosted in deformed and altered metavolcanics and metasediments of the Carolina Slate Belt. Emphasis includes the successful use of … Read more
Stall or aerodynamic stall of axial-flow fans has long been recognized as an important operational problem in mine ventilation. To develop a technique for characterizing fan stall in multiple-fan ventilation networks, a research project was initiated through the Generic Mineral Technology Center for Mine Systems Design and Ground Control. Considering that fan stall is related … Read more
Bacterial sulfate reduction has been identified as one process by which constructed wetland systems remove contaminant metals from coal and metal- mine drainage. Under anaerobic conditions, sulfate-reducing bacteria oxidize simple organic compounds (CH2O) with sulfate, and thereby generate hydrogen sulfide and bicarbonate ions: SO4-² + 2CH2O → H2S + 2HCO3-…………………………………………..(1) Hydrogen sulfide reacts with many contaminant … Read more
The electric operation and design features of the 11,000 H.P. variable speed SAG mill gearless drive is presented. The function of the frequency-converter, control system drive and lubrication systems are described. An analysis of the harmonic characteristic in the Supply System and Motor is presented, and the dynamic development of the stator current, speed and … Read more
The complex geology of the ore body prevented good segregation of a pure oxide fraction in sufficient tonnages to maintain the two circuit operation. Before plant start-up, Freeport recognized that small quantities of carbonaceous ore added to the oxide circuit would produce unacceptable reductions in gold recovery. The carbonaceous ore contributed sufficient preg-robbing organic carbon … Read more
Rare earth element (REE)- and gold-bearing breccia pipes are a potentially significant economic target in the Pea Ridge iron ore mine, Washington County, Missouri. The Pea Ridge deposit is one of eight known volcanic-hosted iron ore deposits in the Middle Proterozoic St. Francois terrane, which are similar to the Olympic Dam-type deposits of Australia. Total … Read more
Arsenic, copper, and molybdenum were effectively removed from arsenic-bearing flue dust using a three-stage continuous sulfuric acid leach. Leach conditions to maximize arsenic and copper extraction while minimizing bismuth extraction were determined: 25-wt pct H2SO4, 20- to 25-wt pct solids, a leach temperature of 55° C, and a 30-min residence time. These conditions yielded arsenic, … Read more
A sulfuric acid leach technique for extracting gallium and germanium from Apex ore without the use of a reducing agent, such as SO2, was investigated. Leaching studies showed that with increasing sulfuric acid concentrations, gallium extraction increased to over 95%, while germanium extraction reached a peak of 71% before decreasing to less than 50%. It … Read more