2/0 THE JOURNAL OF GEOLOGY. 



Below the magnetite-actinolite-schists and separated from the 

 nearest exposure by a covered interval of 50 feet is the outcrop 

 of quartzite discovered by Pumpelly and Credner. The outcrop 

 runs about 175 feet along the strike and 30 feet across it. At 

 the N. E. end the strike is about N. 55 °E., and at the S. W. end 

 about N. 20° E., the dip in both cases being to the W. of 

 N.,40°-45°. For the most part the rock is massive and heavily 

 bedded, but the higher portion shows unmistakable sedimentary 

 banding, and even false bedding. 



In external appearance and in composition the rock is a very 

 coarse-textured, light-colored quartzite, made up almost entirely 

 of quartz, with some muscovite and chlorite as subordinate con- 

 stituents. Under the microscope, probably because obliterated 

 by shearing, no original rolled grains were seen, although sev- 

 eral slides were examined. Red garnets are occasionally found 

 in the quartzite. 



A short distance south and west of the quartzite is a ridge 

 running a little east of north, made up mainly of granite, which 

 presents several bold faces to the west. Near the south end and 

 on the west side, is found upon the granite a westerly dipping 

 fringe of conglomerate, which extends some 50 feet along the 

 strike, as a continuous rock mass. Farther north occasional 

 small patches of conglomerate on the northwesterly sloping 

 granite faces, indicate that the contact follows very closely the 

 direction of the ridge, and lies near its western base. 



III. Granite. 



The granite exposed on this ridge occurs in both white and 

 reddish weathering varieties, which appear to be, however, iden- 

 tical in composition and age. The rock is a coarse mixture of 

 quartz and feldspar of which orthoclase is an important part, and 

 which occurs in Carlsbad twins up to two inches in length. 

 Light colored mica and biotite are largely developed in the 

 planes of shearing. The granite contains much pegmatite, both 

 in veins and in irregular masses. From the contact with the 

 conglomerate back as far as exposures extend, the granite is 



