THE MINERALOGRAPHY OF THE FELDSPARS 



371 



analyses are given in the following tables, together with analyses 

 made for the writer from material supplied by Dr. Samuel G. Gordon 

 of the Philadelphia Academy of Science. As it agrees with the 

 description of the original material there is but little doubt that it is a 

 good representative. Under the microscope it is at once seen to be an 

 intergrowth of a barium-bearing orthoclasic feldspar, hyalophane, 

 and a potash rich albite. Quantitative microscopic measurements^ 

 resulted as follows: 



The distribution of the four components as obtained from recast- 

 ing Penfield and Sperry's analyses into the two phases must be 

 somcithing like this: 



This grouping agrees well with the extinction angles: 



Potash phase (oio) i8° 



Soda phase (oio) 6° 



and the specific gravity: 2.692. 



The results of recasting Croasdale's analyses can be arranged in 

 a similar manner as follows: 



See Part I, pp. 248-59, for an outline of the method used. 



