INTRODUCTION 



Missouri district can be expected to turn up in the 

 future; the major hope lies in the development of 

 some new methods of prospecting, as, for example, 

 methods that would indicate the probability of de- 

 posits in the absence of surface ontcrops." Drilling 

 in the mid-1950's on the west side of the Southeast 

 Missouri district resulted in the discovery of the 

 large unexposed deposits of lead ore known as the 

 Viburnum Trend. By 1970, half a dozen mines were 

 operating, and the reserves of lead in Missouri alone 

 had increased to 30 million tons. (See the chapter 

 on "Lead" in this volume.) The Viburnum Trend 

 will yield more lead than the total production of the 

 old part of the district. With the phoenixlike reju- 

 venation of the Southeast Missouri district, the 

 Viburnum Trend becomes the perfect example of a 

 potential resource converted to a reserve. 



We see no reason why such discoveries and de- 

 velopments cannot be expected to continue in the 

 future. To point the direction to potential resources 

 and to attempt to evaluate them are the objectives 

 of this book. 



OUR DEPENDENCE ON MINERALS 



Few people are fully aware of their daily depend- 

 ence upon minerals. An awareness is growing as 

 the fragilities of modern civilization, stemming 

 from population growth and economic expansion, 

 become recognizable not only as world and national 

 problems, but also as personal problems. The avail- 

 ability of mineral resources to meet the projected 

 demands will critically affect future events. 



It is important, therefore, to be able to predict the 

 occurrence of minerals, with some degree of realism, 

 on several different scales of both time and space; 

 we must know not only in which direction a particu- 

 lar mine opening should be extended to continue in 

 an ore body, but over a longer time period, we must 

 know where prospecting and exploration should be 

 concentrated to discover new deposits of each kind 

 of mineral — and the likelihood of success. In other 

 words, where are our potential mineral resources 

 and how large are they? How long will they last? 

 For which minerals, if any, are we "in good shape"? 

 Is our supply of any minerals unlimited? Of which 

 ones do we have very little, or are we likely to run 

 out in the near future? For these, is there a geologic 

 probability that more can be discovered in the 

 United States? — that is, are there geologic environ- 

 ments in which such minerals are likely to occur? 

 If so, where? And what problems are likely to be 

 encountered in finding and extracting them? If 

 domestic resources are not likely to be sufficient, 

 then to which parts of the globe must we look for 



adequate resources in the future? These are the 

 questions to which the authors of this volume have 

 addressed themselves. 



CLASSIFICATION OF RESOURCES 



What, then, is a mineral resource? To begin with, 

 we may define a mineral resource as a concentration 

 of elements in a particular location in or on the 

 earth's crust (or, now, also in the oceans), in such 

 a form that a usable mineral commodity — whether 

 it be an element (such as iron or aluminum), a 

 chemical compound (such as salt or borax), a min- 

 eral (such as emerald or asbestos), or a rock (such 

 as marble, coal, or gypsum) — can be extracted from 

 it. The perceptive reader will recognize that such a 

 definition has little practical value if the particular 

 mineral commodity cannot be extracted at a profit. 

 As already suggested, this feasibility of profitable 

 extraction, or economic availability, is one of two 

 parameters that distinguish between resources and 

 reserves ; the other parameter is the degree of cer- 

 tainty of existence. These two parameters were 

 originally formulated into a classification of re- 

 sources by V. E. McKelvey (1972), whose presenta- 

 tion of these concepts is so vital to the philosophy 

 of resources, and whose classification is so impor- 

 tant as the cornerstone of the present volume, that 

 we have included his article as the second chapter 

 of this volume. We will summarize McKelvey's re- 

 source classification by stating merely that he de- 

 fines reserves as economically recoverable material 

 in identified deposits, and applies the term resources 

 to include "deposits not yet discovered as well as 

 identified deposits that cannot be recovered now." 

 The terms recoverable, paramargmal, and sub-mar- 

 ginal designate successively lower degrees of eco- 

 nomic recoverability ; paramarginal resources are 

 defined as low-grade resources that are recoverable 

 at prices as much as 1.5 times those prevailing now, 

 and submarginal resources are those of still lower 

 grade. (See fig. 4, p. 12.) 



In this volume we use a similar classification of 

 resources ; but because of our conviction that the 

 long-range potential lies in resources that have not 

 yet been discovered, our classification places less 

 emphasis on the definition of various levels of eco- 

 nomic recoverability, and more emphasis on evaluat- 

 ing the undiscovered — defining the various degrees 

 of certainty. For the purpose of this volume, we 

 distinguish three different such degrees (fig. 1). 

 Identified resources are specific bodies of mineral- 

 bearing rock ivhose existence and location are 

 known. They may or may not be evaluated as to 

 extent and grade. Identified resources include 



