Resources of Metals

In conclusion, it may be mentioned that the characterization of the mechanical behaviour of materials has many facets. Different methods of testing pertain to different aspects and conditions. The tensile properties, as determined by the tensile test, correspond to slowly applied single load applications. Rapidly applied and cyclic load applications respectively provide the impact and the fatigue properties. Hardness is an analog of the tensile strength which a tensile test measures. The creep test pertains to mechanical behaviour under long term loading at elevated temperatures. 

Present account provides a preliminary knowledge of the processes leading to mineral formation. The coverage is amply illustrated. The account has also made references to re- 

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The foregoing has been a brief and general account of the environmental impact that ensues from the processing of sulfidic resources of metals. For obvious reasons, a major emphasis has been placed with regard to the copper industry in the presentations. It will be worthwhile for the reader to become more acquainted with this area, which has featured in as many as twenty papers contained in the proceedings of the EPD-96 Congress (see Literature). 

The indispensable element, copper, will run out a few years later and by the year 2150, the only metals in widespread use with known ore reserves will be iron and chromium. The situation appears even more serious if we assume an exponential increase in metal consumption, such as has occurred since 1960, for on this basis, all known metal reserves would be exhausted within 50 years, with the exception of iron and chromium. Although the latter scenario is the most pessimistic possible and takes no account of the possibility of the discovery of new ore reserves, the overall picture is alarming whatever figures we choose as a basis for calculating the length of time metal supplies will last. The urgent need to conserve non-renewable resources of metals therefore reinforces the need to prevent pollution problems arising from their dispersion in the environment. The two problems are complementary. 

In addition, on the basis of analogous specimens, the accumulation of damage and plastic deformation of metal structure were simulated. These results provide the possibility to obtain the prediction charts of the metal work s residual resource. 

Total known world resources of platinum-group metals have been variously estimated as between 68,000 (7) and 96,000 metric tons (8). Assuming the former estimate and 1979 levels of demand, these reserves should be sufficient to supply the Western world weU into the twenty-fourth century. Reserves and relative proportions of the PGMs in the larger deposits are given in Tables 5 and 6. Relative amounts of the PGMs vary from deposit to deposit. 

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

Resources. World resources of silver are estimated to be about half a million tons. However, only about 250,000 metric tons are considered economically recoverable reserves. These are associated with ores of copper, gold, lead, and 2inc, and extraction depends on the economic recovery of those metals. Canada and the CIS vie for the greatest reserves of silver in the ground. 

Production and trade figures are pubUshed by the U.S. Bureau of Mines (22), the American Bureau of Metal Statistics (23), the Canadian Department of Energy, Mines, and Resources (24), and the World Bureau of Metal Statistics (25). Production figures are often incomplete because of the need to avoid disclosure of proprietary data. Hence, marketing data is often estimated. 

The extraction of metals fundamentally relies on their availability in nature. Three terms are important while one refers to availability. One is the crustal abundance and the other two are the terms resources and reserves. The average crustal abundance of the most abundant metals, aluminum, iron and magnesium, are 8.1%, 5.0% and 2.1% respectively. Among the rare metals titanium is the most abundant, constituting 0.53% of the Earth s crust No metal can be economically extracted from a source in which its concentration is the same... 

Finally, it may be added that it is the terrestrial resources which have served and will continue to serve as practically the sole suppliers of metals and materials. Among the other resources only the manganese nodules extracted from the ocean bed have drawn serious attention the world over for exploring economic methods of processing. 

Sources of metals or the mineral resources are distributed quite non-uniformly over the Earth s surface. No country can claim that it has domestic supplies of all the minerals it needs. The situation and outlook as to the availability of minerals thus varies from country to country and commodity to commodity. 

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