PETROGRAPHIC 1 GEOLOGY AND DESCRIPTIONS. 833 



Quartz schist. Quartxyte. Gal)bro.] 



t 



Meg. Fine-grained, siliceous, supposed to be a portion of the Animikie. 



Mic. The groundmass is of fine interlocking quartz. There are two micas, viz., 

 biotite and muscorite, the latter of later origin than the biotite and the quartz which 

 form inclosures within it. The muscovite forms larger plates than the biotite and 

 by its colorlessness and its high double refraction is easily remarked. The biotite is 

 usually older than the quartz. Pyrite in scattered small grains is quite abundant. 

 Among the interlocking quartzes is occasionally a grain of a striated feldspar, while 

 larger grains of low birefringent power have characters that show en n I it- rite. One 

 section. 



Age. Animikie. N. H. w. 



No. 2056. QUARTZ SCHIST. 



Same place, same bluff, but higher up, toward the gabbro. 

 Ref. Annual Report, xxiv, page 27. 



Meg. Siliceous, but fine grained. 



Mif. .Mostly quartz, but much coarser than in the last. There are many feld- 

 spathic grains indistinctly triclinic, but so much weathered that they are completely 

 dimmed by microscopic inclusions. They sometimes lie within the quartzes, but 

 usually they share in the interlocking plexus. Biotite is not very conspicuous, but 

 varies from brown to greenish gray in small scales. One section. 



Age. Animikie. N. H. w. 



No. 2057. QUARTZYTE. 



Same place, same cliff, still higher, 150 feet above the lake, near the top of the ridge, dipping 60 to 70 

 southerly. 



Ref. Annual Report, xxiv, page '28. 



Meg. Fine grained and gray, siliceous. 



Mic. Quartz, principally, but mingled with play ioclase and with biotite, composes 

 this rock, including also a little pyrite. The feldspars are decayed by weathering. 

 One section. 



Age. Animikie. N. H. w. 



No. 2058. GABBRO. (Ophitic.) 



Same place, 150 feet south of the foregoing, but not much higher. 

 Ref. Annual Report, xxiv, page 28. 



Meg. Coarse, gray. 



Mic. The magnetite in one instance is sui'rounded by a fringe of brown liutitr 

 which penetrates the surrounding feldspars as if it were of older date. The olivine 

 is quite fresh, about cotemporary with the feldspars and apparently fay a lite. The 

 auyite shows a diallage structure in a few grains, and frequently surrounds the 

 olivines. One section. 



Age. Cabotian. N. H. w. 



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