97
At present the argument remains mostly theoretical
and speculative, but if the quantities of ore available
do not increase rapidly at each lower grade, real costs
can be expected to increase markedly in the future as
more and more extraneous material must he removed to
obtain each additional ton of metal. A ton of ore must
be processed in order to obtain just twelve pounds of
29
copper under current conditions, for example. Xf the
grade of ore processed were to fall to 0.5 percent,
2,bOO pounds of ore would have to be handled to obtain
the same twelve pounds of metal, and at a grade of 0.4
percent, the amount of ore handled would rise to 3,000
pounds. Under conditions of constant technology, one
would expect costs to rise as a result. But, if
substantially greater amounts of ore were available
at each lower grade, resort to still lower grades could
proceed at a reduced pace, thereby allowing advancing
technology the time to combat potential cost increases
more readily. If the grade of ore fell rapidly to the
29
This does not include non-mineral material
that must be handled to get to the ore. In 1969, 622
million short tons of waste material were handled to
obtain 226 million short tons of crude copper ore.
For iron ore, 171 million short tons of waste material
were handled to obtain 229 million tons of crude iron
ore. U.S. Department of the Interior, Bureau of Mines,
"Technological Trends in the Minerals Industries (Metals
and Nonmetals Except Fuels)," in Preprint from the 1969
Bureau of Mines Minerals Yearbook (Washington, D. C.:
Government Printing Office, n.d.), p. 5, Table 1.