516 



GEOLOGY OF CENTRAL WISCONSIN, 



SI 



"bi 



quartzite is indistinct. 

 North of and overly 



At the southern end of the section the "Jaws of the 

 Narrows " horizontal sandstone layers, altematingly hard 

 and quartzitic, and soft and friable, are seen abutting 

 against and overlying heavy beds of north ward- sloping, 

 pinkish-gray, dark-gray, and purple, vitreous quartzite 

 (1273, 1274). The exact contact of the two formations is 

 finely exposed, the sandstone filling the cracks between the 

 layers of quartzite and including large detached masses of 

 the latter rock. A short distance northward, along the wall 

 of the gorge, this quartzite is terminated by a steep ravine, 

 on the north side of which comes in the veined quartzite 

 that forms the body of the ridge. This curiously veined 

 rock (1267, 1275) may be described as a light to dark-red- 

 dish, sometimes purple, usually somewhat vitreous, quartz- 

 ite, which has 

 been shattered FIG. 33. 



g & throughout into 

 -e small, sharply 



-q angular frag- 



J 3 ments, and 



|j *~ these cemented 



00 jT together again 



S by milky-white 



.515 vein quartz, the 



j| * numerous cavi- 



5 ties in which 



8.2 



8 1 are lined with 



a , o- small, brilliant, 



03 .. 



," and very per- 

 _; feet quartz crys- 

 ^S tals. The ex- 

 . tensive fissuring 

 3 '3 to which this 

 g | rook has been 



c.j^ subjected is indicated not only in the interlacing veins of 



1'| white quartz, which often make up half the mass, but al- 



E so in the frequent juxtaposition of different looking f rag- 



7,s5 ments of the quartzite. Certain portions of the rock are 



jsj more fissured than other neighboring portions, and then 



. 9 1 appear like wide veins into which numerous fragments 



o " of the wall rock have fallen. Fig. 33 represents a small 



"g g area, two feet by one and a half feet, of the veined 



a 3 - quartzite, the white representing the vein-quartz, the 



* black the fragments of red quartzite. In some of the crys- 



tal-lined cavities a soft white coating is noticed on the crys- 



Q , tals. The same material is seen sometimes lying loose in 



^ the cavities and again filling minute cracks in a more com- 



r pacted condition. According to Prof. Daniells' analysis it 



contains silica, 53.15 per cent , and alumina, 45.09 per cent., 



the balance being water. The bedding of* the veined 



It appears to stand at a high angle to the northward. 



ing the veined rock is another bait of quartzite (1277) without 



-farilie 



VEINED QUABTZITE. 



