THE ARCHAEAN ROCKS. 



489 



liigh ground trenclmg north and south, which rises 200 to 300 feet above the Wisconsin 

 at Wausau. In tlio S. E. qr. of Sec. 21, on tlie south slope of part of this ridge, a 

 peculiar, fine-gi-ained felspathic rock (937, 945) is exposed, and is quarried to some ex- 

 tent on Mr. Kolter's land. This rock has a brownish-pink color, the least weathered 

 portions showing a grayish tinge, is ratlier fine-grained, and has a marked granular 

 texture, looldng almost like a mechanical rock. The most abundant ingredient is a 

 pinkish felspar in cleavable fragments up to j'^th inch across. With this is much 

 granuliir brownish quartz, and a little blackish mica in fine flakes, making the rook a 

 granite. No arrangement of the minerals in parallel lines is perceptible. In the quarry 

 the rock is seen to be nearly horizontal, dipping not more than 10° in a due south direc- 

 tion. A total thickness of about three feet was seen. Large tliui slabs, 2 inches to 4 

 inches thick, sphtting off parallel to the bedding, can be obtained. 



Near Single's Mill, in the noi-th part of S. E. qr. of Sec. 29, in the same township, 

 and on the edge of a part of the same high ground, are exposures of a whitish, slaty, 

 granular quartzite (936), in places iron-stained. Under the magnifying glass this rock 

 is seen to be made up of rounded grahis of glassy quartz. Some few places were noted 

 where the variety with granular texture grades into a non-granular glassy quartz. - 

 Scales of silvery mica occur on the surfaces of laminae. The bedding structure is distinct, 

 and shows a strike of N. 75° E. and dip of 56° S. E. 



About haJf a mile from this place, and on the south side of the valley of Little Rib 

 river, S. E. qr. Sec. 29, the northeast face of a ridge shows quartzite in large exposures. 

 The rock here (935) is glassy, translucent, and occasionally iron -stained, resembhng that 

 of Rib Hill. The' bedding is obscure. On the slope of the hill below, the roots of the 

 trees of a heavy wind-fall have upturned numerous fragments of a brownish-pink, gran- 

 ular-textured felspathic rock, similar to that at Kolter's quany in Sec. 21. Half a mile 

 northeast on the north face of the same elevation, N. E. qr. S. E. qr. Sec. 80, a high 

 ledge shows the same felspathic rock, striking N. 80° E., and dipping 50° N. W. 



At the falls of Rib river, S. E. qr. Sec. 28, T. 29, R. 5 E., are large exposures of 

 greenish chloritio schist ajid syenite. On the south side of the river, at a point near the 

 lower left hand comer of Fig. 18, is a rocky point about 15 feet high, showing heavily 

 but distinctly bedded, greenish syenite, dipping 20° E., and striking N. 8° W. The up- 

 permost layer (950), 3 feet thick, is 

 Fig. 18. moderately coarse-grained, mottled 



green and grey, weathering white. 

 To the lens it shows much grayish 

 quartz, green amphibole, and white 

 altered felspar, the last least abund- 

 ant, though coarsest of the three. In 

 some specimens greenish chlorite ac- 

 companies the hornblende. The nest 

 layer below (948), 4 feet tliick, is a 

 very much finer - grained, almost 

 aphanitic, greenish-grey rock, con- 

 containing apparently a good deal of 

 chlorite. Tire weathered surface is 

 white, with numerous green, epidotc- 

 colored blotches. Microscopic exam- 

 ination shows that the ingredients of 

 thjs fine-grained rock are the same 

 as those of the coarser one above, but 

 that the amphibole and felspar arc 

 both more altered. This rock breaks 



^fcH^^^^ 



tTiectcon on ifie line B.C.I'E, 



BOTK OCCUKBBNOES AT THE FALLS OF RlB RrvBB. 



Scale, fiTty feet to the inch. 



