702 THE GEOLOGY OP MINNESOTA. 



[Gabbro. Diabase. Muscovadyte. Quartzyte. 



No. 1360. GABBRO. 



South side of Gabemichigama lake ; probably in N.^E. J sec - 6 > T - 64 ~ 5 w - 

 Ref. Annual Report, xvi, pages 92, 122. 



Meg. The ordinary gabbro, somewhat decayed and coated with a green mineral, 

 probably malachite. No section. 



Age. Cabotian. u. s. G. 



No. 1361. DIABASE. 



About on the town line between T. 64-5 and T. 64-6 W., south side of Gabemichigama lake. A basaltic 

 dike at the shore. 



Ref. Annual Report, xvi, pages 92, 122. 



Meg. Heavy and firm, dark, medium grained. 



Mic. Although the ophitic structure is evident, still there were many of the 

 augites which were as early in origin as the feldspars. These are small and roundish. 

 The later ones are frequently interlaminated with the feldspars, which, in a few cases, 

 have taken fantastic shapes, with spreading, recurving branches like a rigid wand. 

 The augites also embrace much of the glassy magma, now charged with magnetite 

 particles. One section. 



Age. Dike in the Keewatin. N. H. w. 



No. 1362. MUSCOVADYTE (ivitli quartz, etc.) 



From near the top of the irony bluff south side of Gabemichigama lake. 

 Ref. Annual Report, xvi, pages 92, 122. 



Meg. Dark, heavy with iron ore, crumbling. 



Mic. Hypersthene, magnetite, quartz make up this slide in the order named, quartz 

 being about one-fifth of the whole, the hypersthene embracing the other minerals 

 poikilitically, and being sometimes stained with hematite. One (thick) section. 



Age. Cabotian (changed Keewatin). N. H. w. 



No. 1364. QUARTZYTE (vnth hypersthene., etc.) 



Near the bottom of the quartzyte bluff, south side of Gabemichigama lake. 

 Ref. Annual Report, xvi, pages 92, 122. Compare No. 118E. 



Mic. Quartz, hypersthene, magnetite, diallage compose this rock, about four-fifths 

 being quartz. In the quartz are numerous small inclusions, generally grouped near 

 the centres of the grains. Finer inclusions run in lines across the quartzes. The 

 hypersthene sometimes embraces all the other minerals poikilitically, forming plates 

 of considerable size, in the manner of augite in a diabase, and also encloses globular 

 grains of diallage and apparently of olivine. Two sections. 



Age. Pewabic (changed jaspilyte of the Keewatin). 



Remark. Considering only the evidence of the slides Nos. 1362 and 1364, it 

 appears that the bottom of the quartzyte bluff is less pyroxenic than the top. That 

 signifies that at this place there is a gradation increasing toward the gabbro, and 



