to us. But they are not limitless. A ton of iron

taken from the earth is gone from the earth. A barrel

of oil or a volume of natural gas once used is gone for

good.

 The most disconcerting feature of minerals is their
 exhaustibility. They are wasting assets. They are
 completely consumed in use if they are fuels; they
 are at least partially dissipated if they are
 minerals. Therefore the questions, "How large are
 the reserves? How much is left in the ground? What
 will happen when it is gone?" are vital questions
 of life and death. For ours is truly a mineral
 civilization which stands and falls on its capacity
 to produce staggering amounts of some minerals and
 varying quantities of many others.(24)

 The problem has not been lessened by increased

production of things other than minerals. The larger is

the amount of production undertaken for defense, manufac-

turing, and services, the greater is our dependence upon

minerals, not less. A large superstructure of activities

has been built by using minerals. It is maintained by

their production.

 One significant thing about American experience

over the past century is the extraordinary extent of its

natural wealth, and the unprecedented speed with which

those resources have been (and are being) consumed. The

former helps to explain our wealth; the latter, our

growing concern with the exhaustion of natural resources.

In this respect the United States may have passed through

a unique phase of its history; so much of what it has

experienced may have been based on non-recurring phenomena.


 24Zimmerman, World Resources, p. 439.