THE MICACEOUS SCHISTS. 199 



shattered, there eau not be deteeted anioiig- tlic iVaij'incnts aiiv tliat ])reseut 

 the least evidence of bein<^' waterworn. Tlicir (juartz (grains are in all 

 cases either very sharp-edyed I'rau'ments or thc\- interlock with the other 

 components l)^- verv irregular sutures. The felds[)ars ]ia\e been fractured 

 also, but in this case too the fragments are very sharp-edged. ( )ccasionallv 

 an altered feldspar has escaped rupture and lias preserved its original form, 

 when it appears as a phenocr^•st in a cataclastic matrix. 



In the most altered phases of the feldspathic schists the tliin sections 

 present a strikingly sedimentary aspect. Rounded grains of (piartz and 

 feldspar are endiedded in an aggregate of secondary substances, just as the 

 grains of (piartz in a sandv slate are embedded in a tine-g'rained aggregate 

 of kaolin, etc. But in this case the rounding of the grains is plainh' due 

 to decomposition (see pp. 1 '.'7-198), since numl)ers of tlieni tliat are side l)v 

 side extinguish simultaneously between crossed nicols. In no instance have 

 any waterworn grains been detected in anv of tliese rocks, and hence none 

 of theni exhibit anv evidence of a sedimentar-s* origin, however nuxch they 

 may at first glance look like sediments. 



The foliation, which all the micaceous scliists exhilnt, is tlie result 

 of the flattening of their larger (piartz and feldspar grains in a uniform 

 direction and the arrangement of the larger l)iotite flakes with their longer 

 axes in the same direction. The cataclastic grains (those formed bv tlie 

 fracture of the larger grain.s) are not necessarilv elongated, though many 

 of them are so, and where thev are their longer axes are not alwavs 

 uniforiidy orientated. Tlie banding of the scliists is due mainh- to the 

 greater abundance of biotite in cei'tain planes than elsewhere 



Whatever niav be the origin of the banding of tliese rocks, it is clear 

 that their foliation is the result of mashing. The liending of large biotite 

 plates, the cracking of the feldspars, and the granulation of tlu- (piartzes, so 

 frequently observed in thin sections, and the presence of cataclastic grains 

 in general, are jiroof that the rocks have been subjected to crushing forces. 

 That there has been mashing is shown also by the streaming of biotite 

 flakes around the porphvritic feldspars. In a rock (specimen No. 1(!T64) 

 from near the NW. corner of see. 2, T. 47 X., R. 30 W. (Atlas Sheet IX), for 

 instance, there is a large Carlsbad twin of orthoclase, surrounded by lines 



