MINERAL RESOURCES OF THE STATE OF NEW YORK 239 



The banks yield products of fine to .medium .grain, with Httle of 

 coarser character, that contain above .90 per .cent quartz. By 

 washing, the silica content may be raised to 98 per cent or .a little 

 more. Besides building sand the deposits yield :fire, core, engine, 

 abrasive and glass sand. The principal banks are at-Humaston, 

 McConnellsville, Rome, Pish Greek and Cleveland. 



Molding sand. The principal deposits of molding sand occur in 

 the Hudson valley in the stretch of 100 miles from Glens 'Ealls south 

 to IQngston. They are part of the terraced deposits that a^e 

 prominently developed along the river and that extend from i to 

 15 miles back from the present channel. The -molding sands lie 

 directly under the soil and are s.ucceeded in depth by deposits of 

 loose, open sand and then by the brick clays, .all of -which were 

 accumulated in the closing stages of the Pleistocene when the valley 

 was occupied by the flood waters of Lake Albany. 



The molding sands represent a phase of the general sand accunaula- 

 tion that at one time must have spread over the whole valley. Since 

 their deposition they have been subjected to erosional agencies of 

 wind and water so that now they have .a somewhat patchy distribu- 

 tion. In places they have been heaped up in dunes which are still 

 shifting about, but mostly they are anchored by soil and vegetation 

 so as to form a more or less even mantle over the day 10 or 15 f^et 

 thick as an average. Through wind .action the sands .have accumu- 

 lated in places within the inner gorge of the river, but as a rule they 

 occur on top of the terraces at altitudes of from 150 to .400 feet 

 above tidewater. 



The sand consists of quartz particles bonded by -plastic clay. 

 When uncovered in the bank it appears as a firm, coherent mass 

 which holds .up in vertical sections ;much like the lunderlying plastic 

 clays. It packs readily in the hand 5,nd retains the impression; 

 whereas the open .sand associated with it has :httle or no bondiag 

 qualities. In the -usual run of commercial sand ."the clayey.-matter 

 represents from one-third to one-fourth of the entire: mass. This 

 statement applies to the finer sizes — the characteristic and amore 

 important products of the district ; the coarser sizes -as a rule contain - 

 less bond. 



The sand particles are characterized by a degree of angularity 

 which is seldom observed in deposits by stream or beach action. 

 This results from the crushing down of the quartz "under tremendous 

 pressure, whereby the conchoidal fracture surface peculiar to that 

 mineral are developed; the common outlines are triangular or 

 crescentic with little rounding of the edges and points of the grains. 



