260 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



the increasing need of the mining industry for geologic advice and 

 to the growing recognition of that need. 



Nonmetals. — In the field of nonmetallic mineral deposits the recog- 

 nition of the need of geologic advice has grown more slowly and in 

 fact can hardly yet be said to be widespread. Nonmetallic mineral 

 resources are in general so abundant, lie so near the surface, and are 

 so cheap, relatively speaking, that producers have given little thought 

 to their geologic aspects. However, it not infrequently happens that a 

 producer, say, of sand and gravel, locates his plant near a talus pile, 

 which he mistakes for a bedded deposit of suitable thickness and 

 quality. When further work discloses that the actual deposit from 

 which the talus is derived is merely a thin cap at a higher elevation, he 

 is faced with the problem of relocating his plant, changing its layout, 

 or abandoning it altogether. 



Some industries in the nonmetallic field utilize underground methods 

 of mining. For example, mica, feldspar, talc, magnesite, gypsum, 

 fluorite, and some phosphates are among the minerals so mined. 

 More recently underground methods have been successfully applied 

 to the mining of limestone, slate, sandstone, and even granite at 

 different places. Special processes for recovering salt and sulphur by 

 underground solution or melting and pumping have been devised 

 which differ from ordinary mining methods, but the successful loca- 

 tion and development of such an enterprise, as in the other instances, 

 depends fundamentally on knowledge of the geology of the area in 

 which lies the deposit to be mined, or otherwise recovered. 



Again supplies of construction materials for building and other 

 activities in the vicinity of large cities or large engineering projects 

 tend to become depleted fairly rapidly and search for such materials 

 has to be extended farther and farther from these centers. Here 

 a good geologic map is of the greatest service whether or not it was 

 originally prepared to serve economic needs. For regional planning, 

 where constructional activities are contemplated, the areal geologic 

 map of the United States has been found a valuable guide for more 

 detailed investigations. Similarly, State geologic maps and geologic 

 maps of individual areas, such as those provided in the folios of the 

 Geological Survey, have repeatedly proved their worth in locating 

 supplies of necessary construction materials. For example, the State 

 geologic map of Alabama shows the distribution in the northern part 

 of the State of extensive deposits of gravel in areas mapped as Tus- 

 caloosa formation and large areas of valuable limestone for building 

 in the Bangor limestone. Special economic maps, such as that of the 

 Tennessee Valley, prepared by the Geological Survey, indicate the 

 distribution of a wide variety of mineral deposits. The use of such 

 information may often result in large savings both in time and money, 



