THE MINING AND QUARRY INDUSTRY I914 53 



SAND AND .GRAVEL 



The production of sand and gravel should be given consideration 

 as one of the branches of the mineral industry. It is carried. on 

 in one or more places in practically every county of the State; but 

 only in a few sections has it become really stabilized so as to be 

 conducted on a more or less permanent basis. For that reason a 

 statistical .investigation of the industry is attended with consider- 

 able difficulty, and the results may be lacking somewhat in accuracy. 



Such is the case more especially with the ordinary building sands 

 and gravels which are so widely distributed that in most places they 

 have little or no intrinsic value, the requirements being supplied 

 from deposits in the immediate vicinity at a nominal expense above 

 the cost of handling. In recent years, however, there has been a 

 manifest tendency toward a standardization of these materials 

 where they are to be employed in important structures or engi- 

 neering works. It has been found that they have a very direct in- 

 fluence upon the quality of the mortar or concrete into which they 

 enter, a fact that has not received so wide appreciation as it should 

 perhaps, outside of the engineering profession. The need for ma- 

 terials that will meet the modern requirements has made necessary 

 more care in the selection, besides preparation oftentimes by sizing 

 or washing. This development is one that promises to place the 

 industry upon a more settled basis than it has had in the past. 



Sand also serves a variety of other uses, such as for glass man- 

 ufacture, for making of molds for casting metals, as an abrasive, 

 and in numerous manufacturing and metallurgical operations. In 

 most of these applications the sands must meet certain definite re- 

 quirements as to physical condition, mineral or chemical composi- 

 tion, which greatly limit the available sources of supply. Their 

 production necessitates a degree of skill and technic which makes 

 for permanency in the enterprises. 



The sand and gravel beds of the State belong mainly to the 

 Pleistocene formations, accumulated as the result of the great ice 

 invasion which moved from north to south and reached as far 

 south as northern New Jersey and Pennsylvania. This ice sheet 

 swept the rocks bare of their former mantle of disintegrated ma- 

 terials and in their place left a covering of transported bowlders, 

 gravels, sands and clays. These materials when deposited directly 

 by the ice as ground moraine are so intermixed as to have little or 

 no industrial value. Such unmodified drift covers a considerable 

 portion of the area, especially in the hilly country, whereas in the 



