ORIGIN OF THE PEGMATITES OF MAINE 



313 



extent the quartz-feldspar ratio is dependent upon the composition 

 of the feldspar. He concluded that the ratio between quartz and 

 feldspar bore no regular relationship to the composition of the feldspar. 

 He believed that in most graphic granites definite ratios did exist 

 between the proportions of feldspar and quartz but that these ratios 

 were not always so simple as Vogt and Johansson had supposed. 



TABLE SHOWING COMPOSITIONS OF GRAPHIC GRANITES 



'■ Calculated from the analyses. 



To supplement the small number of available trustworthy analyses 

 the writer collected specimens of graphic granite from the Fisher 

 feldspar quarry in Topsham, Maine, and from Kinkle's feldspar 

 quarry in Bedford, N.Y. These were analyzed by Mr. Geo. Steiger 

 in '' laboratory of the U.S. Geological Survey. In order that the 

 material analyzed should represent closely the true composition about 

 lo-pound samples of the Maine occurrences were taken. These 

 were pulverized, carefully mixed, and quartered down to convenient 

 size for analysis. The New York specimen was a cleavage piece 

 about 2X3X1 inches in size. 



The ratio of quartz to feldspar in the analyses published by Vogt 

 and Bygden and in the author's analyses are given in the table above. 



