560 W. C. PHALEN 



characteristic of ordinary uncrushed vein quartz in thin sections 

 (see Fig. 4), the sections are iine-grained mosaics with crystallo- 

 graphic boundary planes entirely absent (Fig. 5). Therefore the 

 most important evidence of derivation from former vein material is 

 absent. Even all signs of internal strain are lacking for the reason 

 that the quartz like all the other rocks of the region has undergone 

 almost perfect recrystallization, that is, molecular readjustment to 



Fig. 4. — Normal structure in vein quartz. From the report of Waldemar Lind- 

 gren on the "Gold Quartz Veins of Nevada City and Grass Valley Districts, California." 

 In Seventeenth Annual Report, U.S. Geological Survey, Part II (1896), PL IV, Fig. a, 

 opposite p. 132. 



the surrounding conditions. The actual tracing of the "pebble" 

 structure, however, into the original quartz vein material is sufficient 

 evidence for another explanation of the phenomenon. 



The results of the examination of the thin sections are given below. 



Several thin sections cut in various directions from the quartz 

 masses were studied in polarized light under the microscope, to 

 determine if possible how deformation took place. These sections 

 were cut as follows: (i) normal to the direction of elongation of the 

 pebbles; (2) parallel to the direction of elongation and to the major 



