Non-renewable mineral resources

The natural resources of the earth's crust upon which industry depends for metals, non-metallics and most of its energy, come from deposits in the crust carrying six to over 1000 times the normal content of the required elements. Such deposits have formed over such long periods of geological time that they must be regarded as non-renewable within the span of existence of the human species. These facts are briefly illustrated by reference to the cases of iron, copper, aluminium, titanium, magnesium, lead, zinc, flourine and the fossil fuels. The possibilities of exploiting much lower concentrations when considered in relation to the exponential rise in demand, lead to the conclusion that the scope is limited unless very cheap energy becomes available.