PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 469 



Granite. Apotrachyto. Gabbro.] 



and it is intergrown with the quartz to form the beautiful micropegmatyte so 

 common in these red rocks. 



One section examined. 



Age. Cabotian. u s G 



No. 646. GRANITE. (Red.) 



" ' Red granite,' southeast corner T. 63-1 E." 

 Ref. Annual Report, x, page 67. 



Meg. A rock quite similar to No. 645, only a little darker colored and of some 

 finer grain. 



Mic. Section composed of reddened feldspar, quartz, much yellowish alteration 

 products and a little magnetite. There is much fine-grained micropegmatyte and 

 many of the feldspars are almost completely saturated with quartz. 



One section examined. 



Age. Cabotian. IT . S- G . 



No. 647. APOTKACHYTE. 



"Red rock, like Nos. 643 and 645, making hills in the northwest corner of T. 62-2 E. and the northeast 

 corner of T. 62-1 E." 



Ref. Annual Report, x, page 67. 



Meg. This rock is very similar macroscopically to No. 645, but a little finer 

 grained. 



Mic. The texture of the rock is clearly porphyritic, the porphyritic crystals 

 being of clouded and reddened feldspars, small in size and sometimes arranged in 

 irregular clusters. The groundmass is also reddened, and consists of an intergrowth 

 of quartz and feldspar, with some Magnetite and yellowish alteration products. Under 

 crossed nicols this groundmass breaks up into the irregular "patchy" areas, which 

 are frequently seen in the devitrified groundmass of the acid rocks.* The patches 

 are composed of poikilitic quartz areas in which are crowded small, much altered 

 feldspars. 



Age. Cabotian. 



Remarks. This rock is thought to have had an original glassy groundmass, 

 which has now devitrified to the '' patchy " aggregate of quartz and feldspar. Com- 

 pare Nos. 68 and 129, and see figure 3 of plate I. u. s. G. 



No. 648. GABBRO (with f/urtz). 



Same locality as No. 647. 



Ref. Annual Report, x, pages 67, 68; Bulletin ii, page 78. 



Meg. A medium-grained, dark-gray, dioryte-like rock, made up of flesh-colored 

 feldspar and much black material which appears to be both magnetite and augite. 



*Cf. F.BASCOM: I'. H. <;,/. Survey, /!ll,ii,i cxxxvi, plan- XVII. figure /). 18SM. R. U. IRVIM;: r. N. f;,,>l. Kun-eu, 

 Mon. v, plate XIII, figures 13 and 14, 1883. 



