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Show Titles and Abstracts 13 If we consider the cost of producing copper as variable, de pending upon economic conditions=-waqes, supplies, etc .........-but the price received as fixed by the government, many large ore bodies might be likened to an orange with a very thick skin. In such deposits the limits of the' ore body (i. e., tons of ore) are not sharply defined, because the copper content is relatively high at the center, but' gradually becomes less as you go outward from . the center until a point is reached where the metal content is too low to yield a profit if the copper-bearing rock is mined as "ore." Let us call this point the point of "cut-off' and let it be, say, 0.4% copper. Any rock containing less than 0.4% copper is worthless skin. This skin or peel of our orange assays from 0.4% copper on the inside to zero per cent copper on the outside. The orange itself assays from 0.4% copper on the outside to a higher value on the inside, say 2% copper. Now let costs increase, while the price remains fixed. Our point of "cut-off" now becomes, say, 0.6% copper. We have a thicker skin and a smaller orange (ton If costs become too high, no nage of ore). profit can be made, and we have no fruit. All is worthless peel. On the other hand, decreasing costs of producing metal from .a large ore body gives more fruit and less skin, and might add hundreds of thousands, even millions, of tons to the ore reserves, and so lengthen the life of the mine. Thus the reduction in costs of operation at a large mine is concerned to an important degree with decreasing the cost of wages and taxes, when the price of the metal is fixed, and has a very practical significance to mining communities, in that prolonging the life of the mine maintains the community at work for a greater time. The same end effect is ob tained, if wages and taxes remain high, if the price for the metal is increased. It will not be as easy to find new ore deposits in the future discover the ore bodies of the past and present, whose location was made plain by geological indications of ore showing plainly at the surface of the. g.round. The large ore bodies of the future are now hidden from view and the next gen eration will need to use all the scientific methods that are available in order to tell us what is below the earth's surface. Great areas that may contain ore bodies are now covered with comparatively thin layers of aluvial material. Progress in recording and inter preting geological data must precede or go with geophysical pros as it has been to "Thus far," to quote an eminent authority, "economic geology is only a haphazard and often fruitless study. We have pecting. little idea what caused the great intrusions of igneous rocks in or near which so many ore deposits are found, to say nothing of ore bodies that are many times as complex and mysterious. Geology sufferers from the handicap that nearly all the evidence is hidden beneath the sua face, but with more careful and widespread record ... |
