314 



EDSON S. BASTIN 



In Fig. 3 the composition of the feldspars are plotted on triangular 

 projection. The numbers on the diagram correspond to those in the 

 table. 



From the table and diagram it is at once evident that even among 

 those graphic granites whose feldspars are almost identical in com- 

 position (such as Nos. 2 to 6) there are quite considerable variations 



Or 



^5-6 



Fig. 3. — Three-component diagram showing the relationships between the 

 molecular percentages of orthoclase, albite, and anorthite in the graphic granites 

 tabulated above. The numbers and letters in table and diagram correspond. 



in the quartz-feldspar ratio. In analyses Nos. 1,2, 3, 7, 8, 10, and 11 

 (particularly in Nos. i, 3, 7, 8, and 10) the percentage of anorthite 

 is small and nearly constant, the only important variation being in 

 the ratio between orthoclase and albite. No regular or consistent 

 relationship is recognizable, however, between this ratio and the ratio 

 between quartz and feldspar. The grouping of Nos. i to 11 near 

 the lower line of the diagram signifies merely that the feldspar asso- 



