QUARTZ-MICA SCHIST 385 



2. Persistence of well developed minute lamination in straight lines 

 for man)^ meters. 



S. Marked variation in mineral content in adjacent laminae, as brought 

 out ij) table 4. 



Table 4. — Mineral Composition of four successive Laminw in a handed Oneiss 



12 3 4 



Gray White Gray White 



Quartz 40.0 51.2 45.0 40.0 



Feldspars : 



Microcline (kaolinized) 56.0 18.8 46.2 32.0 



Micropertliite 4.0 24.4 2.0 23.6 



Accessories : 



Biotite 6.8 2.0 



Ilmenite 5.5 2.4 



Zircon 0.1 .... 



Totals 100.0 100.0 100.0 100.0 



Locality, one mile west of Seidersville, AUentown quadrangle; the same as 

 that of specimen No. 1, table 2 (5781). 



Graphite-bearing Quartzite 

 character 



Many of the features of this formation have been previously described/^ 

 but some will be noted here to show how analogous it is to the preceding 

 one. The phase which can be regarded as most closely approaching the 

 original unaltered rock is a bluish gray quartzite, made up of interlocking 

 grains of quartz interspersed with more or less parallel flakes of graphite. 

 The most noteworthy accessory constituents are apatite, biotite, garnet, 

 pyrite, and zircon. In thin section the bluish hue of the quartz is often 

 seen to be connected with the presence of included carbonaceous dust, as 

 typically shown in the section, figure 10. iipatite and garnet are at times 

 more prominent in this rock than they are in the quartz-mica schist. 

 Round zircons are frequent, as in that rock. In contrast to the quartz- 

 mica schist, however, unchanged beds are rare in the graphite-bearing 

 formation, feldspathization having almost always taken place to a marked 

 degree, as described below. 



Table 5 presents counts of the areas occupied by the minerals in sec- 

 tions of three specimens of the quartzite phase. 



Ben.1. L. Miller : Loc. cit. 



