GEOLOGY OF FRANKLIN COUNTY 97 



These rocks have at best only a very obscure foliation. They 

 are cut by numerous quartz and pegmatite veins, and frequently 

 become quite coarse themselves for a short distance. 



Two types of structure are found which grade into one another. 

 In the first type there are evidences of cataclastic structure. 

 Larger feldspars occur, which become broken down at the edges, 

 producing fragments whose origin from the parent fragment is 

 often apparent. But no instances have been seen in which this 

 structure is well marked, as in the case of the similar gneiss from 

 Trembling mountain cited by Adams. 1 In much of the gneiss in 

 fact, little or no sign of this structure is observable, but the feld- 

 spars are even sized, with highly irregular boundaries against one 

 another, which often become very jagged and interpenetrate. 



The quartz occurs largely in small idiomorphic individuals in- 

 cluded in the feldspars, this being the case in the rocks with no 

 sign of cataclastic structure, but only to a slight extent in the 

 other type. The remaining quartz consists of fairly large indi- 

 viduals, always with rounded outlines, and usually of elongated, 

 often greatly elongated, shape. These spindle-shaped quartzes 

 are optical wholes, though showing pressure effects by an un- 

 dulatory extinction which is not uniform over the whole but 

 breaks up the crystal into several patches. It seems to the writer 

 that the peculiar shape and character of the quartz is best ex- 

 plained as a result of a slow recrystallization, molecule by mole- 

 cule, under the stresses of metamorphism, the optical anomalies 

 shown resulting from slight subsequent strains applied to the 

 rock. 



In many parts of the region gneisses are found which are 

 precisely like those here described except that they contain 

 pyroxene in addition to the hornblende. Between these and other 

 gneisses composed essentially of pyroxenes and feldspars, which 

 are, next to the granitic gneisses, the most widespread rocks of 

 this group, many intermediate varieties occur. 



lAdams, F. D. Geol. sur. Canada. New series, v. 8. pt J. p. 42. 



