BULL. GEOL. SOC. AM. 



VOL. 10, 1898, PL. 39 



Figure 1.— Photomicrograph of a Thin-section of Orthoci.ase 



Cut parallel with basal pinacoid to show infiltration of secondary albite along the pris 

 niatie cleavage. Actual diameter, 2.5 millimeters, crossed nicols 



FuilllE i. — PHUToMlCROiatAl'H i>F A ThIN-SKCTIUN OF IIASIC INCLUSION 



Piece taken from left land inclusion in the granite shown in plate 38, figure 2. Dark 

 mineral is hornblende, the sliaded one plagioelase, and the white one quartz, .\ctual 

 diameter, 4 millimeters. 



PHOTOMICROGRAPHS OF ORTHOCLASE AND BASIC INCLUSION IN GRANITE 



