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NEW YORK STATE MUSEUM 



to a friable sandstone (as do the Potsdam and New York Oriskany) 

 and in some places even to loose sand. The disaggregated and 

 friable portions are used as glass sand. A comparison of the 

 analyses shows that the two are similar in composition and there 

 seems to be no reason why the Oriskany sandstone of New York 

 should not be used for glass making. 



It is possible that the rock at Oriskany Falls may be somewhat 

 calcareous in places, since the maximum thickness is small and it is 

 associated in the field with the Helderbergian and the Onondaga 

 limestones ; this seems to be the only argument against its use. The 

 samples analyzed did not contain much lime, however. 



The glass sands of the Oneida lake region seem to be suitable for 

 the manufacture of the commoner grades of glass ; it will probably 

 be impossible to improve their quality by washing. 



The quartzite phase of the Potsdam, the Poughquag quartzite and 

 the quartzites and conglomeratic quartzites of the Shawangunk are 

 not suitable for the manufacture of glass because of the difficulty 

 and expense involved in crushing and sizing and because of their 

 poorer qualit}^ 



Manufacture of ferro-silicon. Considerably greater variation in 

 composition appears to be permissible in quartz rock used in the 

 manufacture of ferro-silicon; the presence of ferric oxide is not 

 objectionable, except in so far as it reduces the amount of silica in 

 the rock. Lime and alumina appear to be undesirable constituents, 

 but no very definite information could be obtained from the several 

 manufacturers visited as to the limiting quantities of lime and 

 alumina allowable; estimates were given ranging from o.io to 4 

 per cent ALOg, less than o.io per cent CaO, and a minimum silica 

 content of 95 per cent. 



The general consensus of opinion was that while it was possible 

 to use a rock carrying as little silica as 95-96 per cent, much more 

 satisfactory results were obtained by using as high-grade rock as 

 could be obtained at reasonable cost. Loosely compacted and friable 

 rock is undesirable; hard, compact sandstones or quartzite give 

 better results. 



PvOck from all the formations described, with the exception of the 

 glass sands of Oneida lake, meets these requirements. 



Some of it seems especially suitable; such, for example, as the 

 Poughquag quartzite from Dutchess county, which carries 99.51 per 

 cent of SiOa, 0.21 per cent FcoOg, 0.15 per cent ALOo, and 0.05 

 per cent CaO, and certain beds of the Shawangunk, which are 

 almost as pure; more especially numbers 5 and 6, table i. 



