Metals, ore minerals

The reason for the similarity of Th-U and rare-metal ore mineralization between silica-undersaturated (nepheline-... 

Industrial rocks and minerals—Rocks of economic value exclusive of metallic ores, mineral fuels, and gems. 

Cemented carbides play a cmcial role in the recovery of metallic ores and nonmetals by underground or open-pit mining practices, recovery of minerals such as coal (qv), potash, and trona, and drilling for oh and gas. The methods of excavation can be broadly classified into three types rotary... 

Uranium is found in most rock, in a concentration of two to four parts per million (ppm). Substantially greater average concentrations can be found in mineral deposits, as high as 10,000 ppm, or 10 percent. Most uranium deposits suitable for mining, however, contain an average of less than 1 percent uranium. Uranium is a metal, and thus its acquisition is not unlike the mining of any other metallic ore. Although uranium is found nearly eveiywhere on the earth, Canada leads the world in uranium production, mostly due to its heavy financial investment m uranium exploration, and to a few sizable deposits in the Saskatchewan territoiy. Table 1 depicts the total world uranium production in 1997. 

Figure 20-20 shows in schematic fashion some of the alternative paths leading from ores to pure metals. These paths include four general processes of which the essential chemical process is reduction to yield the neutral metal. First is separation. Generally, a metal ore obtained from a mine contains a particular compound of some desired metal mixed with various other materials. The mineral must be separated from these other contaminants. Separation often is followed by conversion, in which the mineral is treated chemically to convert it into a form that can be easily reduced. The third step is reduction. After a suitable compound has been obtained, it is reduced to free metal by chemical reaction with a reducing agent or by electrolysis. The metal obtained by reduction often contains small amounts of impurities, so the final step is refining to purify the metal. 

SD and S O. 8D and of the ore fluids responsible for epithermal Au-Ag and base-metal vein-type deposits in Japan have been estimated from analyses of fluid inclusions (Hattori and Sakai, 1979) and minerals (Watanabe et al., 1976). These data are shown in Fig. 1.103. 8D values of ore fluids for epithermal Au-Ag vein-type deposits are similar to those of present-day meteoric water values. 8D values of epithermal ore fluids for base-metal vein-type deposits are slightly higher than those of epithermal Au-Ag vein-type deposits. This may be due to the boiling of epithermal base-metal ore fluids and involvement of seawater. 

D and 5 0 data on fluid inclusions and minerals, 8 C of carbonates, salinity of inclusion fluids together with the kind of host rocks indicate that the interaction of meteoric water and evolved seawater with volcanic and sedimentary rocks are important causes for the formation of ore fluids responsible for the base-metal vein-type deposits. High salinity-hydrothermal solution tends to leach hard cations (base metals, Fe, Mn) from the country rocks. Boiling may be also the cause of high salinity of base-metal ore fluids. However, this alone cannot cause very high salinity. Probably the other processes such as ion filtration by clay minerals and dissolution of halite have to be considered, but no detailed studies on these processes have been carried out. 

Casadevall, T. and Ohmoto, H. (1977) Sunnyside mine. Eureka mining district. Sun Juan County Geochemistry of gold and base-metal ore deposition in a volcanic environment. Econ. GeoL, 72, 1285-1320. Cathelineau, M. and Nieva, D. (1985) A chlorite geothermometer. The Los Azufres (Mexico) geothermal system. Contr. Mineral. Petrol., 91, 235-244. 

White, D.E. (1968) Environments of generation of some base metal ore deposits. Econ. Geol., 63, 301-335. White, D.E. (1969) Mercury and base-metal deposits with associated thermal and mineral waters. In Barnes, H.L. (ed.), Geochemistry of Hydrothermal Ore Deposits. New York Holt, Rinehart and Winston, pp. 575-631. 

All ore mineral deposits lie in or on solid rocks of which the Earth s crust is predominantly composed. The geological processes which are responsible for the formation of rocks also form the ore bodies associated with them. For the formation of an ore body, the metal or metals concerned must be enriched to a considerably higher level than their normal crustal abundance. The degree of such enrichment below which the extraction cost makes the processing of the ore uneconomical is termed the concentration factor. Typical values of the concentration factor for some of the common metals are given in Table 1.5. 

Sulfuric acid is often made as a byproduct of the mining of naturally occurring metal sulfide ores (mineral deposits). To purify a metal from an ore, the ore is heated in a process called smelting. 

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