72 NEW YORK STATE MUSEUM 



I 



The molding sand occurs directly under the soil and is succeeded 

 by a layer of loose or " open " sand of variable thickness. The 

 latter is usually of coarser nature and does not pack like the mold- 

 ing sand. It has a grayish color from admixture of shale with the 

 quartz grains. Below this layer is found the Hudson river clay, 

 yellow on top, changing to blue in depth. 



The features surrounding the field occurrence of the sand appear 

 to be exceptional for a simple water-laid deposit like the sand, 

 gravels and clays that underlie it. It is not a definite bed or layer 

 interstratified with the others and exposed at certain horizons, nor 

 does it appear to have any counterpart in the series. It contrasts 

 with the underlying sands in its fine, even grain, in its evidences 

 of a weathered condition and in the fact that except for the inter- 

 mixed clayey material is a very fine quartz sand. In its distribu- 

 tion it has the character of a surficial mantle that varies in thick- 

 ness rather rapidly and also changes in vertical altitude more than 

 would be expected from an undisturbed water-laid stratum. 



The characteristic fine-grained sands which form the principal 

 material shipped to foundries are made up of angular , to subrounded 

 quartz grains. Under the microscope the individual grains are fre- 

 quently observed to possess sharply concave sides which are natural 

 fracture surfaces of the quartz, developed no doubt by granulation 

 under pressure. This points to a glacial source which, of course, 

 is generally accepted as the origin for the whole series of detrital 

 deposits, but there appears to be some indication of additional 

 abrasion by other agencies. The angles are more or less rounded 

 and the grains may show frosted or pitted surfaces, features sug- 

 gestive of wind action subsequent to that of the ice. 



Sufficient details of the field occurrence of the sand have not been 

 assembled as yet to justify any conclusions as to the process by 

 which the sand has attained its present distribution and attitude 

 toward the other deposits. In some places, however, there is strong 

 resemblance to eolian deposits, with modifications arising from their 

 fixation by plant growth and subsequent weathering. Live sand 

 dunes exist in the vicinity of the molding sands. Their materials 

 are similar to the latter with the difference that they are not so 

 well sorted and lack the weathered appearance which is always 

 found in the true molding sands. It seems quite probable that the 

 finer particles of these shifting sands are being sorted out by the 

 winds and distributed over the surrounding area and may thus con- 

 tribute some share to the upbuilding of the molding sand layer. 

 There is little question that weathering influences by the breaking 



