MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 



17 



that of a large population of deposits, a few contain 

 most of the ore (for example, Slichter, 1960 ; Kauf- 

 man, 1963). In the Boulder Dam area, for example, 

 4 percent of the districts produced 80 percent of the 

 total value of recorded production. The petroleum 

 industry in the United States has a rule of thumb 

 that 5 percent of the fields account for 50 percent 

 of the reserves and 50 percent of fields, for 95 per- 

 cent. And in the USSR, about 5 percent of the oil 

 fields contain about 75 percent of the oil, and 10 

 percent of the gas fields have 85 percent of the 

 gas reserves. 



The other feature of interest is that in many de- 

 posits the grade-tonnage distribution is also log 

 normal, and the geochemists have found this to be 

 the case also with the frequency distribution of 

 minor elements. 



These patterns of size- and grade-frequency dis- 

 tribution will not in themselves provide information 

 on the magnitude of potential resources, for they 

 describe only how minerals are distributed and not 

 how much is present. But if these patterns are com- 

 bined with quantitative data on the incidence of 

 congeneric deposits in various kinds of environ- 

 ments, the volume or area of favorable ground, and 

 the extent to which it has been explored, they might 

 yield more useful estimates of potential resources 

 than are obtainable by any of the procedures so far 

 applied. Thus, estimates of total resources described 

 in terms of their size- and grade-frequency distri- 

 butions could be further analyzed in the light of 

 economic criteria defining the size, grade, and ac- 

 cessibility of deposits workable at various costs, 

 and then partitioned into feasibility-of -recovery and 

 degree-of-certainty categories to provide targets for 

 exploration and technologic development as well as 

 guidance for policy decisions. 



Essential for such estimates, of course, is better 

 knowledge than is now in hand for many minerals 

 on the volume of ore per unit of favorable ground 

 and on the characteristics of favorable ground itself. 

 For petroleum the development of such knowledge 

 is already well advanced. For example, whereas most 

 estimates of resources have been based on an as- 

 sumed average petroleum content of about 50,000 

 barrels per cubic mile of sediment, varied a little 

 perhaps to reflect judgments of favorability, the 

 range in various basins is from 10,000 to more than 

 2,000,000 barrels per cubic mile. As shown by the 

 recent analysis by Halbouty and his colleagues 

 (1970) of the factors affecting the formation of 

 giant fields, the geologic criteria are developing that 

 make it possible to classify sedimentary basins in 

 terms of their petroleum potential. Knowledge of 



the mode of occurrence and genesis of many metal- 

 liferous minerals and of the geology of the terranes 

 in which they occur is not sufficient to support com- 

 prehensive estimates prepared in this way. But for 

 many kinds of deposits enough is known to utilize 

 this kind of approach on a district or regional basis, 

 and I hope a start can soon be made in this direction. 



NEED FOR REVIEW OF RESOURCE 

 ADEQUACY 



Let me return now to the question of whether or 

 not resources are adequate to maintain our present 

 level of living. This is not a new question by any 

 means. In 1908 it was raised as a national policy 

 issue at the famous Governors' Conference on Re- 

 sources, and it has been the subject of rather ex- 

 tensive inquiry by several national and international 

 bodies since then. In spite of some of the dire pre- 

 dictions about the future made by various people 

 in the course of these inquiries, they did not lead 

 to any major change in our full-speed-ahead policy 

 of economic development. Some of these inquiries, 

 in fact, led to immediate investigations that re- 

 vealed a greater resource potential for certain 

 minerals than had been thought to exist, and the 

 net effect was to alleviate rather than heighten 

 concern. 



Now, however, concern about resource adequacy 

 is mounting again. The overall tone of the recent 

 National Academy of Sciences' report on "Resources 

 and Man" was cautionary if not pessimistic about 

 continued expansion in the production and use of 

 mineral resources, and many scientists, including 

 some eminent geologists, have expressed grave 

 doubts about our ability to continue on our present 

 course. The question is also being raised interna- 

 tionally, particularly in developing countries where 

 concern is being expressed that our disproportionate 

 use of minerals to support our high level of living 

 may be depriving them of their own future. 



Personally, I am confident that for millennia to 

 come we can continue to develop the mineral sup- 

 plies needed to maintain a high level of living for 

 those who now enjoy it and raise it for the im- 

 poverished people of our own country and the world. 

 My reasons for thinking so are that there is a 

 visible undeveloped potential of substantial propor- 

 tions in each of the processes by which we create 

 resources and that our experience justifies the be- 

 lief that these processes have dimensions beyond 

 our knowledge and even beyond our imagination at 

 any given time. 



Setting aside the unimaginable, I will mention 

 some examples of the believable. I am sure all geolo- 



