568 R. C. ALLEN 



in the disintegration and subsequent sedimentation of the disinte- 

 grated particles of the underlying granite which in many places it 

 resembles so closely that distinction is difi&cult. There are phases 

 of the arkose in which the feldspar crystals show little perceptible 

 wear, much less the quartz grains. It is particularly difficult to 

 separate from granite in places near the contact where secondary 

 mica has developed and veins of quartz and pegmatite occur like 

 those in the granite. Phases in which there has been perceptible or 

 conspicuous rounding of the quartz and feldspar particles are com- 

 monest and these may be either massive or schistose. The schis- 

 tosity in the arkose is the result of mashing of the feldspars, by 

 which process the quartz grains are generally not greatly affected. 

 Where the arkose is overlain by the iron formation and particularly 

 by iron ore, as in the mines north and west of Gwinn, it is in many 

 places highly decomposed, soft, and iron stained, the feldspars 

 being largely kaolinized. 



The conglomerate is much less abundant than the arkose and 

 according to drill records is not present in most localities. Its 

 occurrence seems to be erratic and, curiously enough, where exposed 

 in the S.E. \ of the S.W. \ of section 19, T. 45, R. 25, it lies some 

 distance above the base of the formation. Drift bowlders of the 

 conglomerate are rather plentiful but the only exposures known to 

 the writer are in the S.W. \ of section 19. Here there are 12-15 

 ft. of it exposed in layers from i to 2 ft. thick dipping about 16° 

 E. and striking N. 15° W. At this locality the contact with the 

 granite is about 150 paces west. The matrix of the conglomerate 

 is chiefly arkose but in one exposure it is siliceous, gray slate inter- 

 bedded with the arkose. The pebbles are up to several inches in 

 diameter and are mainly vein quartz which is abundant in the under- 

 lying granite. There are also many fragments of green schist, 

 dense, vitreous, gray quartzite and siliceous, cherty, slightly dolo- 

 mitic slate of grayish-green color. The composition of the con- 

 glomerate may also be studied to advantage on the waste dump of 

 the Gwinn mine in the N.E. \ of the N.W. \ of section 28 where a 

 bowlder bed was encountered in cutting the pumping-station in the 

 shaft. All of the bowlders are well rounded and vary up to 6 to 7 

 inches in diameter. The matrix is arkose so decomposed that many 



