POTAS 
@ 
ORTHOCLASE 
MICROCLINE 
8 
@ 
ORTHOCLASE 4»> MICROCLINE 
PERTHITE 
ANORTHOCLASE 
© 
ALBITE 
SODA FELDSPA 
Fic. 19.—Plot of 954 recast chemical analyses of natural feldspars. The 
chemical analyses and are not those which the writer would employ in many cases 
plagioclase feldspars contain considerable amounts of the potash component. The 
