OF THE ROCKS 



OF LAKE 



SUPERIOR. 



231 



185. Metamorphosed sliale — very cellular; resembles No. 117, but is not so much 

 altered ; the cells are, many of them, filled with zeolites. 



186. Volcanic grit — much altered. In general appearance, approaches the erup- 

 tive rocks ; contains zeolites. Prevailing colour, red. 



187. Volcanic tufa — wrinkled like No. 161 ; amygdaloidal, the cells filled with 

 zeolites ; colour, dark brownish red. The original material seems to have been, in 

 part, brecciated. 



188. Volcanic grit — highly ferruginous ; dark iron-rust colour; fracture irregu- 

 lar, somewhat nodular ; is like the ferruginous beds associated with the conglome- 

 rates at other localities. Filled with calcareous and magnesian minerals. 



189. Same as No. 188, for the most part, but is lighter-coloured, and of less spe- 

 cific gravity, although more compact. It gradually changes, in some localities, to 

 a very compact gritstone, containing nodules of Thomsonite. 



190. Same as No. 188. Amygdaloidal; colour, dark red, light red, and reddish 

 gray ; fracture, very irregular and uneven ; contains zeolites and thalite. 



191. Volcanic grit — so filled with grains of the thalite as to give to the rock a 

 green colour, not unlike that of some of the eruptive traps. 



192. Same as No. 188. Very ferruginous ; amygdaloidal; the grit fine-grained, 

 and of a purplish-red colour. The cells filled with thalite and zeolites. 



193. Same as No. 188. Very ferruginous; few amygdules; finely granular; 

 small grains of thalite and zeolites liberally disseminated through the mass ; tole- 

 compact. Makes a near approach to the ordinary red sandstones in general ap- 

 pearance. 



194. Conglomerate — pebbles of amygdaloid, in a paste of red ferruginous mate- 

 rial ; the paste amygdaloidal, and resembling the overlying rock, No. 192. Disin- 

 tegrates easily. Traversed by veins of calcareous spar, and various zeolites, prin- 

 cipally laumonite. 



195. Siliceous shale — unaltered; very quartzose ; fine granular; colour, gray. As 

 the neighbouring trap is approached, the rock takes on precisely the appearance of 

 the quartzites of Black River, Wisconsin River, and other places, as Snake and 

 Kettle Rivers. In some places, small fragments of jasper are disseminated through 

 the rock. 



196. Greenstone — same as the Fond du Lac rock, No. 432. 



197. From alternating beds of volcanic grit, metamorphosed shale, and, perhaps, 

 metamorphosed sandstone. Some of the beds are compact quartzite. 



198. Volcanic grit — amygdaloidal ; colour, reddish gray ; the cells filled with 

 thalite and many grains of the same disseminated through it. 



199. Same as No. 198. Very ferruginous; colour, red; granular; no amygdules. 



200. Same as No. 198. More compact, and approaching more nearly to the 

 ordinary red sandstones. 



201. Brecciated conglomerate — fragments from one to two inches in diameter; 

 some few larger ; generally angular, sometimes rounded ; colour, red ; amygdaloidal ; 

 very hard ; brittle ; many of them porphyritic, and appears to have been derived 

 from the red quartzose porphyry, No. 251. The paste is lighter-coloured than the 



