HIGH-GRADE SILICA MATERIALS 29 



The writer is of the opinion that the resuhs of the toughness test 

 should not be too heavily weighted in considering the availability of 

 this material for tube mill uses. 



The best rock in the series for this purpose is the Poughquag 

 quartzite from Ward Ladue's farm, Dutchess county ; the structural 

 habit of this rock (figure 6), and its relative purity (table i ; Pough- 

 quag, Dutchess CO.) recommend it highly for .trial in an actual test 

 run. 



CONCLUSIONS 



From field, laboratory and microscopic studies of high-silica rock 

 it is evident that within the borders of the State of New York there 

 is rock of good quality, easy of access, capable of being readily 

 quarried, and which may be used for : 



1 Glass making 



a The Potsdam sandstone, Johnstown 

 b The Potsdam sandstone, Moira-Bangor 

 c The Oriskany sandstone, Oriskany Falls 

 d The Oneida glass sands 



2 Ferro-silicon manufacture 



Rock from all the formations enumerated 



3 Silica refractories 



a The Poughquag quartzite, especially that phase seen on 



Ward Ladue's farm, in Dutchess county 

 b Certain beds of the Shawangunk 



4 Tube mill liners and pebbles 



a More especially that phase of the Poughquag quartzite on 

 Ladue's farm, which appears to be well suited to the 

 purpose 



b Possibly the Poughquag in the vicinity of Peekskill 



c Possibly certain beds of the Shawangunk 



