Ch. 26] DISTRIBUTION IN THE UNITED STATES 481 



Durability. A sand mixture may deteriorate and lose its bond 

 strength as a result of dehydration or vitrification of the clay bond, 

 so that the same mixture cannot be used again. This vitrification of 

 the clay may cause agglomeration of the sand particles. Some sands 

 may deteriorate more rapidly than others. To keep the sand up to 

 its original strength more bond may have to be added. Naturally 

 bonded sands have a lower durability than synthetic sands (Covan, 

 1942). 



DISTRIBUTION OF FOUNDRY SANDS IN THE UNITED STATES 



Foundry sands are widely distributed in the United States and are 

 worked at a number of localities. Most deposits are Pleistocene or 

 Recent in age. All types of sediments — marine, lacustrine, fluviatile, 

 glacial, and eolian, if they have suitable properties, are used. In gen- 

 eral there are two types of deposits: (1) siliceous sands free or nearly 

 free from clay, and (2) naturally bonded sands. 



Those of the first group vary in age from Cambrian to Quaternary 

 and may be consolidated or unconsolidated. They require crushing as 

 well as screening and perhaps even washing after quarrying, whereas 

 those of the second group may need similar treatment after digging. 



The consolidated sands occur in a number of states. They include 

 the Cambrian and Oriskany sandstones of Pennsylvania and Car- 

 boniferous sandstones of Ohio; the St. Peters sandstone of Minnesota, 

 Wisconsin, and Missouri, and the Ottawa sand of the Illinois district. 

 The last named is especially important, and the product of this dis- 

 trict is shipped as far as California and the Northwest. A Cambrian 

 sandstone is also quarried at Portage, Wisconsin, and used for foundry 

 sand. 



In the Las Vegas district of Nevada are extensive deposits of Juras- 

 sic sandstone which is shipped to California in large amounts because 

 that state is deficient in high-silica sandstone. The material has to 

 be crushed, screened, and, in some cases, washed before shipment. 



In California are extensive deposits of siliceous sandstone which for 

 the most part are moderately soft. They are chiefly marine deposits of 

 Eocene age, but many of them are felclspathic in character and do not 

 always run high enough in silica to be useful in steel foundries. In 

 Alabama, Carboniferous sandstone (Hartselle formation) has been 

 quarried for foundry use. Other sands have been quarried in Arizona. 

 Unconsolidated siliceous deposits are worked in New Jersey, where 

 most of the material comes from the Cohansey (Tertiary) formation. 



