PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 675 



Granite. Porphyryte. Gabbro. Diabase.} 



No. 1265. GRANITE. (Red. ) 



Brule mountains, north from Pine mountain. 

 Ref. Annual Report, xv, pages 62, 119. 



Meg. " Red rock." 



Mic. Consists chiefly of recldened feldspars, dimmed by much impurity and by 

 general decay. Some can be seen, however, to be twinned on the albite plan. In 

 some small angular spaces quartz is generated. There is a little magnetite, some 

 hornblende and apparently pyroxene, and some red crystals of hematite( ?) Two 

 sections. 



Age. Cabotian. 



Remark. It is evident, in one slide, that the extinction in the quartz grains 

 governs that in the surrounding feldspars, which are permeated by it, and which 

 give place to it sometimes in the manner of a micro-pegmatyte. N. H. w. 



No. 1265A. PORPHYRYTE (?) 



On the Grand Marais and Rove Lake wagon road ; probably near the crossing of the North Brute river, 

 which is in the N. W. % sec. 32, T. 64-1 E. From a boulder. 

 Ref. Annual Report, xvi, page 63. 



Meg. The rock has a very tine-grained, brownish-gray groundmass, in which 

 are numerous large, tabular, red, porphyritic crystals of feldspar, some of which are 

 an inch across. There are also areas, apparently amygdaloidal, which are filled 

 with a yellow mineral, probably epidote; also similar areas filled with a soft, dark- 

 green mineral, probably chlorite. No section. 



Age. Cabotian. u. s. o. 



No. 1269. GABBRO. ( Weathered. ) 



North side of sec. 19, T. 64-1 E. 



Ref. Annual Report, xvi, pages 64, 66, 119. 



Meg. Dark, coarse grained. 



Mic. The ophitic structure is still evident, although the augite is now trans- 

 formed largely into a dull-gray substance which in the centres and other parts of 

 the augite masses extinguishes 'in alternation with the rest. The rock contains, 

 along with the evident plagioclases, considerable amounts of magnetite, of apatite 

 and of a dull yellowish chloritic substance, the result of alteration, probably of olivine 

 and of the augite. One section. 



Age. Cabotian. N. H. w. 



No. 1273. DIABASE. 



Just west of the rapids going out of North lake. 

 Ref. Annual Report, xvi, pages 65, 119. 



Meg. Dense, trap-like rock. 



