Ch. 27] PRODUCING MINERALS FROM SEDIMENTS 487 



geology. Nevertheless there are mining problems to which knowl- 

 edge of sedimentation can be applied to good advantage. 



Although it would be possible to describe some principles of sedi- 

 mentation that might be applied to the exploitation of sedimentary 

 deposits, such a description is not permitted by the space available 

 here, nor is it in keeping with the purpose of this symposium. Instead, 

 the principal purpose of this chapter is to acquaint students of sedi- 

 mentation, as well as workers in related fields of geology and engineer- 

 ing, with the nature and breadth of the field — the variety of sedimen- 

 tary minerals and rocks currently mined, the general problems en- 

 countered, and the methods commonly used to solve them. 



SEDIMENTARY ROCKS AND MINERALS CURRENTLY CONSIDERED 



VALUABLE 



The sedimentary minerals and rocks currently considered valuable 

 are listed in Table 2, which shows the dollar value of their domestic 

 production in 1946.* A study of this list shows (1) that the number 

 of minerals and rocks currently mined is large; (2) that they are 

 diverse in chemical, mineralogical, and physical characteristics and 

 occur in every major class of sedimentary rocks — in fact, virtually 

 every type of sedimentary rock or mineral, in some degree of purity 

 or physical state, is utilized for some purpose; and (3) that most of the 

 minerals and rocks currently mined are non-metallics, most of which 

 are valued for their content of a chemical compound, like sodium 

 chloride or calcium carbonate, rather than of a single element, or for 

 their physical properties, such as hardness, plasticity, grain size, state 

 of aggregation, or color. Most of the non-metallics have a low unit 

 value. To be commercially competitive, therefore, deposits of most 

 of the minerals and rocks must be of exceptional purity or quality, 

 must be close to tidewater or market, or be so situated or constituted 

 that they can be mined or refined at very low cost. 



PROBLEMS ENCOUNTERED IN THE PRODUCTION OF MINERALS 

 FROM SEDIMENTARY DEPOSITS 



Basically the problems involved in the production of minerals or 

 rocks from sedimentary deposits do not differ from those connected 



* Sedimentary deposits which owe their value to leaching, enrichment, or 

 other types of redistribution of primary constituents, are excluded from the tabu- 

 lation. Examples of deposits excluded are the Lake Superior iron ores, the 

 Colorado-Utah vanadium ores, and the Tennessee phosphates. 



