HIGH-GRADE SILICA MATERIALS 2.J 



The quartzite phase of the Potsdam, at Fort Ann, contains beds 

 of sufficient purity, also, but the beds are thin and too widely 

 separated by less pure material. 



The saccharoidal sandstones of the Potsdam and the Oriskany 

 sandstone at Oriskany Falls are likewise ideal material so far as 

 composition is concerned, and provided unweathered material is 

 used some of these rocks are sufficiently firm and compact in 

 structure likewise, although not so desirable in this respect as the 

 quartzites. 



Provided these rocks were used for the manufacture of glass, 

 the waste, or strippings, of less pure beds would probably be of 

 sufficiently good quality for the manufacture of ferro-silicon. 



It is evident, therefore, that all these formations contain rock of 

 sufficiently high grade for use in the manufacture of either ferro- 

 silicon or carborundum. 



The manufacture of silica refractories. In the manufacture of 

 silica brick it has been found that quartzite with medium to strongly 

 interlocking grains give the best results; the silica content should 

 not fall below 97 per cent. 



Mr P. H. Bates, of the Bureau of Standards, Pittsburg branch, 

 has kindly furnished the writer an abstract article by Donald W. 

 Ross, entitled " Silica Refractories," which will appear in the near 

 future in the Journal of the American Ceramic Society ; in this very 

 interesting article are enumerated the requirements to which high 

 silica rock should conform in order to be available for use in the 

 manufacture of silica refractories. 



Of the formations studied, only the Shawangunk conglomerate 

 and the Poughquag quartzite contain material which meets the con- 

 ditions. 



There are certain conglomeratic-quartzite beds in the Shawangunk 

 which have the requisite firmly interlocked structure (figures 8 and 

 9) and the necessary purity (table I ; Shawangunk, nos. i, 5 and 6). 



Particular attention is called, in this connection, to the Poughquag 

 quartzite on Ladue's farm, in Dutchess county (figures 5 and 6) ; 

 this rock is very highly indurated, has an intricately interlocking 

 structure, and contains 99.51 per cent silica (table I ; Poughquag 

 quartzite, Dutchess county). 



It appears to be equal, if not superior, to the various quartzites 

 mentioned in the article by Mr Ross, which are sources of supply 

 for the manufacture of silica refractories, and seems to merit 

 further investigation. 



