522 GEOLOGY OP CENTRAL WISCONSIN. 



in length, and 40 feet high. Over inost of the hill the rock (756, 758, 764, 765) is quite 

 uniform on a fresh fracture, though presenting a weathered surface from bright pink to 

 dull grayish-pink in color. The weathering is very shght, however, and the rock shows 

 almost no tendency to decompose. It has a medium grain, close texture, is of a bright 

 pinkish color, and vrithout sign of arrangement of the ingredients in Hnes. These are : 

 rather large-flaked, pinkish, clcavable felspar, predominating; somewhat granular, 

 fine, pinkish, translucent quartz, abundant; and greenish-black mica, sparsely scattered, 

 in blotches made up of veiy fine flakes. In places, thin light-green epidote-colored 

 seams occur (757). Somewhat irregular N. W. joints traverse the rock which is, how- 

 ever, for the most part structureless, and is quarried by iiring, the pieces that crack off 

 presenting a conchoidal fracture. On the north side of the west end of the mound oo- ' 

 curs a vertical layer (or vein?) three feet wide, trending N. 55° E., of a soft greenish, 

 higUy scliistose, decomposing chloritic rook (758). The least weathered specimens show 

 a blacldsh color and some tendency to a crystalline textm-e. The vein is weatliered 

 down for two or three feet below the enclosing granite walls, both of which are seen. 

 The schistose laminEe are parallel to the walls. Greenish epidote seams in the I'ock near 

 by have 'the same trend as the vein. Though this granite might be son-,ewhat difficult 

 to obtam in dressable masses, it would undoubtedly make a very handsome and durable 

 stone. 



The Maeion Geanite Areas. 



"In the the town of Marion, T. IS, R. 11 E. Waushara county, are three low granite 

 knobs. Two of these, Stone and Pine Bluffs, ai-e on the N. E. qr. Sec. 27, about two 

 nules in a N. N. W. direction from the quartz-porphyry hill of tlie town of Seneca, 

 Green Lake county; and the thh-d, a larger and bolder hiU, Hes on the eastern border 

 of the marsh, on Sees. 12 and 13, and stretches to some extent over the line into the 

 town of Wan-en, On aU of these areas the rock (766, Sec. 27; 767, 768, Sec. 12) ob- 

 served is nearly the same, a pinkish felspathic granite, mottled with gray and green, 

 closely resembling the Montello granite, from which it differs, however, ui having a 

 coarser grain, less dose texture, and a marked tendency to decompose. Reddish cleav- 

 able felspar is the principal ingTcdient, occurring in facets up to Ju'th and ,^4th inch in 

 diameter; quartz is abundant, fine-granular and translucent; mica is sparse, and 

 scattered in small, greenish-black blotches. Large whitish porphyritic felspar occurs. 

 There is no sign of any arrangement of the ingredients, or of any parallel grain to the 

 rock. No definite bedding planes were observed on any of the outcrops, though numer- 

 ous crossing joint planes occur, and quite regular flat slabs are sometimes obtainable. 

 Veins of white quartz occur. The most marked characteristic of the rock is its tendency 

 to weather and shell off in crumbhng masses. Some of the large flat surfaces are so far 

 cnnnbled as to be penetrated readily by a horse's hoof. The rock from these outcrops 

 would pohsh easily, but its tendency to crumble renders it less valuable than the Mon- 

 tello granite. 



Conclusions. As indicated by tlieir common character and strike 

 direction, as well as their relative positions, the quartz-porphyry and 

 granite patches of Columbia, Marquette, Green Lake and Waushara 

 counties, which have been described in the foregoing pages, are doubt- 

 less to be regarded as but projecting points of one northeastwai'd 

 trending belt, the i-est of which is buried beneath the Silurian sand- 

 stone and later superficial deposits. All, both granites and porphy- 

 ries, belong evidently to the same formation. Moreover, the occur- 



