480 



GEOLO&Y OF CENTRAL WISCONSIN. 



Pig. 14. 



graiute <iud smaller caies of white quartz. In some of the veins, quartz, felspar, and 

 granite aU occur separately, as, for instance, in the one shown in Fig. 14. 



The vein rock here 1 799}^) is a fine-grained 

 admixture of quartz and pinlrish felspar, mica 

 being almost wholly absent. The vein, and its 

 ramifications as weU, are sharply defined from 

 the wall rock. A short distance up stream from 

 this vein the gneiss shows an exceedingly fine 

 lamination, and becomes much contorted (799). 

 The lamination is due in part to a general 

 stratified structure of the rock, independently of 

 its ingredients, but in part, also, to an aggre- 

 gation of the fine black mica along the surfaces 

 of laminte. The ingredients of the rock are fine- 

 grained, colorless quartz, predominating; coars- 

 er, pinkish, translucent quartz; black, shining, 

 small-flalced mica, very abundant; and small-fa- 

 ceted, white felspar. The exposure of contorted 

 gneiss is quite abruptly limited up stream, by 

 a large, pinkish granite mass, which stands 6 to 

 10 feet above the surrounding rock at No. VII 

 of the map. The rock of this large vein (798) is 

 similar to that of the vein la,st described, but is 

 somewhat more quartzose. Next above the 

 granite vein is a fine-grained, fclspatliic gneiss 

 (797), striMng N. 35° E., dipping 80° N. W., 

 and intersected by numerous croos-joints. Next 

 above this are again high exposures of fine- 

 grained, strufctureless, pinkish granite (796), re- 

 sembling the masses and veins further dovsm, 

 but much larger in size. 



At VIII of the map, fine-grained, greenish- 

 brown gneiss (795) is exposed, striking N. 50° 

 E., and dipping 45° N. W., and composed of 

 sUvery mica, pinkish felspar, and translucent 

 quartz. A short distance above, this grades 

 into a coarser kind (794), which is very plainly 

 laminated, in places even schistose, and carries 

 small greenish opidote ( ?) veins. 



In the Rapids at Stevens Point, on Sees. 

 32 and 81, T. 24, R. 8 E., are some considera- 

 ble exposures, which are, however, not so large 

 as those at Conant's Rapids, a mile below. 

 The localities of the main outcrops in the Ste- 

 vens' Point Rapids are shown on tlie map. Fig. 

 ^ V2. At tlie point IX of the map, on the south 

 line of Sec. 32, is alow exposure, at tlie water's 

 edge, of a moderately course, laminated, brown- 

 ish-stained mioacoous grieiss (785), stiiking N. 

 45° E., and rhpping 70° to 80° N. W. This 

 rock is composed of abundant brUhant black mica, which weathers brownish; coarse 

 faceted, plainly striated, wlute felspar; and Umpid quartz. The weathered surface is 



Granite QuarTz 



□ 



PinTc 

 Teldsfior 



Granite Vein at Conant's Bapids. 

 Scale, 6 feet to the inch. 



