24 



NEW YORK STATE MUSEUM 



Burchard ^ gives analyses of glass sands of different quality, list- 

 ing a sand containing 99.99 per cent silica and a slight trace of ferric 

 oxide, as fit for the manufacture of the highest grade of glass; 

 sands containing from 0.006 to 0.0 11 per cent FcsOs are judged 

 suitable for tableware, plate glass, lamp chimneys, etc., and material 

 sufficiently pure for making window glass carries 0.021 per cent 

 FcsOs. Numerous analyses of sands of possible value for glass 

 making range in silica content from 96.45 to 98 per cent and in iron 

 oxide from 0.33 to 0.84 per cent. 



Table 2 





Before washing 



After washing 





Per cent 



Si02 



Per cent 

 Fe203 



Per cent 



Si02 



Per cent 

 FezOs 





98.84 

 96.83 

 99.22 

 98.99 

 95.08 

 99.71 



0.09 

 0.17 

 0.06 



O.IO 



0.24 

 0.08 



99.05 

 97.46 

 99-54 

 99.33 



97.46 

 99.82 



0.06 



Potsdam, Johnstown (poorer bed) 



. 20 



Potsdam, Moira-Bangor, no. i 



O.OI 





0.12 



Potsdam, Moira-Bangor, no. 3 



O.IS 





0.06 







These rocks crush readily into granular "sand," which is improved as to 

 the silica content by washing; in most cases the percentage of ferric oxide 

 has likewise been lowered, but two of the determinations may be question- 

 able. The results at least suggest that some of this material may prove to 

 be of economic value for glass making. 



Table 3 

 Sieve tests 



20-mesh 



30-mesh 



60-mesh 



lOO-mesh 



Per cent 



Per cent 



Per cent 



Per cent 



100 



96.8 



60.8 



10 



100 



70 



22.5 



5.3 



100 



96 



38.4 



10.4 



100 



91-3 



14-7 



2 



100 



69.8 



12.3 



1.8 



100 



100 



96.2 



25.7 



200-mesh 



Potsdam, Johnstown, no. i . 



Potsdam, Moira, no. i 



Potsdam, Moira, no. 2 



Potsdam, Moira, no. 3 



Oriskany, New York 



Oneida glass sand 



Per cent 

 1.5 

 o.S 

 2.2 

 0.5 

 0.3 

 0.7 



The Potsdam and Oriskany samples were crushed in a mortar through a 

 20-mesh screen, washed and dried; the Oneida glass sand was washed and 

 dried. 



According to the judgment of Fettke," sand used in the manu- 

 facture of the best grades of optical glass should not contain more 



^ Burchard, Ernest F., Requirements of Sand and Limestone for Glass 

 Making; Geol. Survey Bui. 285, p. 452-58, 1906; idem; Glass Sand of the 

 Middle Mississippi Basin ; same publication, p. 459-72. 



2 Fettke, Charles R., The Glass Sands of Pennsylvania. Science, n. s., 48, 

 1230, 98-100; July 26, 1918. 



