418 THE GEOLOGY OP MINNESOTA. 



[Quartzyte. Diabase. Sandstonr. 



In another section, the rock, though bearing this number, is a granular 

 quartzyte, with but little else besides quartz. Scatteringly disseminated are a few 

 nests of biotite scales, somewhat radiatedly arranged and associated with chlorite. 

 There are also a few spicules of magnetite. 



The rock represented by this section is very certainly a condition of the 

 quartzyte of the locality. N. H. w. 



No. 553. QUARTZYTE. 



Near the portage trail to Parker ville, at the north shore of Pigeon point. 

 Ref. Annual Report, x, page 48. 



Mey. Firm, gray quartzyte. 



Mir. The section consists essentially of angular and sub-rounded grains, lying 

 in a matrix which consists of finer grains of the same, and of particles that are finely 

 granular, as if from a composite rock. The latter are not so transparent, and often 

 quite cloudy with a chloritic substance, and between crossed nicols remain nearly 

 dark continually. They have a deceptive resemblance to devitrified glass. 



One section. 



Age. Animikie(?) N. H. \v. 



No. 554. DIABASE. 



From the east end of the most easterly island separating Washington harbor from Grace harbor, Isle 

 Royale. It has somewhat the appearance of an imperfectly basaltic dike, but as it develops a few rods further 

 north it appears as an overflow; at least it lies on other trap and amygdaloid. It forms a little harbor where 

 tishing shanties are erected. 



Ref. Annual Report, x, page 48. 



A dark-brownish, fine-grained diabase. Scattered through the rock are 

 small greenish areas (chlorite) and also reddish ones. To the latter is due the 

 brownish cast of the rock. 



Mic. The section shows a diabase composed rffeldxpt/r, <iu</i1c and -incj/iirfitc. 

 The whole rock is much changed and now contains abundant dirty greenish and 

 reddish alteration products. Part of these products are due to the change of the 

 feldspar and augite, but it seems as if some of the reddish material was from an 

 original glassy base. 



One section. 



Age. Cabotian. u. s. <;. 



No. 555. SANDSTONE. (lied. ) 



Isle Royale. Overlies the conglomerate of the west end ofjsle Royale. Resembles No. 548 of Grand 

 Portage island. Has regular bedding, with strata sometimes thirty inches thick, extends for several miles. 

 making islands and points. Specimen is from Siskiwit point; dip 10 to 20 S.; apparently has a thickness of 

 300 or 400 feet. A gritty shale separates the quartzyte from the conglomerate. 



Ref. Annual Report, x, page 49; Annual Report, xiii, pages 100 (No. 165) 103; Bulletin viii, page xxxiii. 



Red, smoothly-weathering sandstone, which might be called a quartzyte. 



