6o NKW V(»KK STATK MUSEUM 



For the various grades of glass, sands of varying purity may be 

 used. For the highest grade such as is used in cut glass ware and 

 in lens-making a pure white sand containing practically lOO per 

 cent (juartz or silica must be used, as a fraction of a per cent of 

 iron will impart a greenish tinge to the glass, the presence of clay 

 will detract from its brilliancy and transparency, while other im- 

 purities will also ruin its value. For the manufacture of window 

 glass and plate glass, where a slight greenish tinge will do no hami, 

 a sand containing as much as one half per cent of iron oxid is 

 frequently safely used, while sands with a slightly greater per- 

 centage of iron, have been used, the color being removed during the 

 fusion by certain oxidizing agents such as manganese or arsenic 

 which oxidizes the green ferrous silicate to a less conspicuous ferric 

 silicate. For the cheaper grades of glass such as are used in bottle 

 manufacture, structural glass, etc., a sand of less purity may be 

 used but rarely does the percentage of silica fall below 97.5. 



Aside from the consideration of the size of the deposit, the dis- 

 tance from railroads or waterways, cost of haulage etc.. the owner 

 of a prospective glass sand deposit should make a thorough exami- 

 nation of his sand under a microscope to determine its probable 

 purity and physical characteristics. The necessary qualifications 

 to be observed by simple tests are summed up by Burchard^ as 

 follows : 



The sand should be nearly white in color; it should be of 

 medium fineness (passing a 20 to 50 mesh horizontal sieve) ; the 

 grains should be uniform in size, even and angular, or, less prefer- 

 ably, they may be rounded. A simple chemical test may be em- 

 ployed by heating the sand in a dilute acid. Effervescence indi- 

 cates the presence of lime; loss of color shows the presence of 

 clay impurities. Iron in the most minute quantities may be de- 

 tected by dissolving sand in hydrofluoric acid- and adding potas- 

 sium ferrocyanid which produces a blue precipitate if iron is pres- 

 ent. Complete quantitive analysis as well as a furnace test should 

 be made as a final determination of the character of a prospective 

 sand. 



Some sands may be partially purified by washing processes wdiich 

 remove clay, mica scales, organic matter, etc. while in some cases 

 where the iron exists as magnetite grains some form of magnetic 

 separation may be effective. 



The glass sand industry has been on the decline in this State 

 for several years and at present the only producing area is that 



1 U. S. Geol. Sur. Bui. 285. p. 454. 



