SILICA SAND 



579 



stone in the eastern interior region and upper Meso- 

 zoic deposits on the east coast are exploited to some 

 extent, but most outcropping silica sandstones de- 

 posited in late Paleozoic and Mesozoic times are lo- 

 cated in the western interior States far from indus- 

 trial users and are therefore not intensively ex- 

 ploited. Marine deposits and dune sands of Cenozoic 

 age are important sources of silica sand along both 

 east and west coasts. 



RESOURCES 



Silica sand and sandstone are among the more 

 common sedimentary formations cropping out in the 

 United States and, in general, their stratigraphic 

 positions, extent, thicknesses, and the areas of out- 

 crop are among the better known aspects of geology. 

 This is true because silica-rich stratigraphic units 

 generally form conspicuous outcrops, and because 

 some have been investigated as possible oil reser- 

 voirs or aquifers. It is unlikely that important silica 

 sand and sandstone units, completely unknown pre- 

 viously, remain to be discovered. Therefore, in a 

 sense, almost all silica sand and sandstone units can 

 be regarded as "identified" rather than as "undis- 

 covered" resources. Parts of these identified re- 

 sources can be allocated to the category of "re- 

 serves." These parts are where certain favorable 

 geologic features fortuitously have combined with 

 favorable geographic circumstances to yield deposits 

 workable under present economic conditions. Favor- 

 able geologic features include chemical purity, uni- 

 form grain size, friability, amenabiliy to beneficia- 

 tion, and proximity to the surface. The favorable 

 geographic circumstances are proximity to markets 

 and to transportation facilities. 



Identified resources of silica sand are virtually 

 inexhaustible, and reserves are very large in rela- 

 tion to demand. Known deposits can satisfy national 

 demands at reasonable cost for centuries. 



PROBLEMS FOR RESEARCH 



Although the United States silica-sand resources 

 are so large that they are unlikely to be depleted 

 by normal use, a large proportion of the most 

 favorably located deposits may be precluded from 

 exploitation by shortsighted public policies. 



Society's mistakes in this respect can be either 

 unconscious or deliberate — unconscious when resi- 

 dential developments are allowed to spread over 

 valuable sand deposits and deliberate when land- 

 use laws are invoked to prohibit exploitation of 

 known deposits in urban areas. The result of pre- 

 clusion is not that we will run out of silica sand. 



but that costs will increase as a result of having to 

 confine mining to areas remote from industrial users 

 and the ultimate consumers. 



Sand and sandstone deposits capable of yielding 

 high-quality silica sand should be identified and pre- 

 cisely delineated on geologic maps — especially on 

 large-scale maps of urban regions. Geologic maps 

 exist for many urban areas, but workable silica-sand 

 deposits are specially designated on only a few of 

 these. Precise location of all deposits in urban re- 

 gions would permit orderly planning for the most 

 beneficial use of land underlain by silica-sand de- 

 posits. 



If geologic reports are to be of maximum utility 

 for the identification of silica-sand deposits, they 

 must include more quantitative data on the physical 

 attributes of the deposits. Geologic descriptions of 

 sandy stratigraphic units commonly stress only 

 those features that can be seen with a hand lens or 

 microscope. These include grain size, sorting, na- 

 ture of the cement, proportions of constituent min- 

 erals, and the roundness or angularity of the grains. 

 In some reports, care is taken to measure these 

 features quantitatively, but rarely do geologists 

 make enough quantitative observations to permit 

 descriptions of the stratigraphic and regional 

 (three-dimensional) variations in these features. 

 Moreover, general geologic descriptions almost 

 never include important physical features such as 

 coherence and the various factors involved in amen- 

 ability to beneficiation. 



Much of the popular opposition to mining in ur- 

 ban areas lies in the unsightly, dangerous, and use- 

 less condition of mined-out areas. Methods for re- 

 storing abandoned pits to esthetically acceptable 

 appearance and productive or recreational use 

 should be developed. Most abandoned pits soon fill 

 partially with water. If the banks are sloped and 

 suitably planted and maintained, these ponds can 

 be converted at moderate cost to parks or recrea- 

 tional and wildlife areas. 



Although the large resources of silica sand are 

 capable of supporting a rapidly increasing produc- 

 tion of disposable glass products (specifically, 

 throwaway bottles), there are vahd and pressing 

 reasons for conservational practices. Wasteful con- 

 sumption will lead inevitably to earlier depletion of 

 nearby high-grade silica-sand deposits and earlier 

 shifts by producers to more distant or lower grade 

 deposits. The direct effect of these shifts will be 

 higher priced glass and more damage to the land 

 surface. The indirect effects will be more pollution 

 in manufacture and, ultimately, more problems in 

 disposing of the product after use. 



