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But men do not Initiate the productive process,
even with extraction; by the time minerals are extracted,
a good deal of production already has occurred. Minerals
spread evenly throughout the earth's crust would be of
little use since most become of value only in concentrated
form, and some, like iron and copper, are used only in
an almost pure state. Fortunately, through various
geological processes, quantities of minerals in a few
places were concentrated sufficiently to allow men to
mine and further concentrate them with relative ease.
Unfortunately, such natural occurrences were limited in
number and extent of concentration. Of late, because
of increasing production, men have moved quickly to
exploit those limited concentrations--at a rate greatly
exceeding the rate of concentration--and therein lies
the rub.
Higher levels of output, which require corre
spondingly higher rates of mining, must lead to eventual
exhaustion of the source, provided the source is not
renewed at a pace at least equal to the rate of withdrawal.
If the source were to become exhausted all at once, then
production that depended upon the steady supply of the
exhausted material also would cease. If, as is more
probable, the source were to become gradually exhausted,
such that the acquisition of each given amount of material
required more and more effort, then real costs figured
in terms of other products forgone would increase and