OF THE ROCKS OF LAKE SUPERIOR. 297 
would, no doubt, become a regular syenite under the influence of metamorphic 
agencies. 
96. Metamorphosed siliceous shale—colour, red. It is changed to a decided quartz 
rock. 
97. Volcanic grit—very ferruginous; resembles Nos. 94 and 95, but has altered 
less since its deposition by the action of intrusive dikes. 
98. Same as 97. Contains less iron, and is lighter coloured. 
99. Volcanic breccia—very amygdaloidal ; full of zeolites, principally laumonite ; 
cells irregular. The fragments appear to have been derived from siliceo-argillaceous 
shale. 
100. Metamorphosed siliceo-argillaceous shale—colour, red; hard; brittle; when 
struck, rings like phonolite; crystals of hornblende, from one-third to half an inch 
long, sparingly disseminated through it. The mass of the rock is dark brownish 
red ; weathered surfaces lighter coloured. 
101. Volcanic breccia—contains small fragments of No. 97. The cement is full 
of zeolites, principally laumonite. It is very loosely aggregated. 
102. Greenstone—fine-grained. The sedimentary rock in near contact with it, 
can scarcely be distinguished from it. 
103. Siliceous shale—thinly laminated ; some of the laminze separated by very 
thin partings of clay. Colour, dark brownish-red ; soft; has a baked appearance ; 
is full of zeolites, which are developed in the partings of the layers and in small 
cavities. The effect of crystallization in some places has been to break up the thin 
layers into fragments, so as to give the rock a brecciated appearance. 
104. Red sandstone—ripple-marked. These beds cannot be distinguished from 
those of St. Louis River, or the south shore of the Lake. Colour, light and dark 
brownish red. Grains small and principally rounded, but there are many angular 
ones. Lines of deposition marked by black stripes. Some of the beds are highly 
charged with oxide of iron, and they differ greatly im specific gravity. 
105. Same as No. 104, without the ripple-marks. 
106. Red sandstone—some of the beds pebbly; the pebbles water-worn ; marked 
by blackish horizontal stripes; a great deal of magnetic iron-sand in the rock, espe- 
cially in the pebbly parts. The formation of these beds is fully illustrated on the 
south shore of the Lake, between Poplar River and La Pointe, where sand, pebbles, 
and iron-sand are being now deposited. 
107. Metamorphosed shale and sand-rock—originally the same as Nos. 105 and 
106. These beds show almost every degree of metamorphosis. Some contain large 
druses filled with ferruginous quartz crystals; some are brecciated; others are 
amygdaloidal ; and some are compact. In the amygdaloidal beds the cells are filled 
principally with calcareous spar. The quartz crystals which line the druses are 
occasionally encrusted with oxide of manganese. 
108, 109. Same as No. 107. 
110, 111, 112. Metamorphosed shales and argillaceous sandstone—passes into 
the purplish red, very compact rock, which rings like clink-stone when struck. 
Shows the passage of the sand-rock into the argillaceous and siliceous shales of Hat 
Point, near Grand Portage Bay. The prevailing colour is dark brownish-red ; some 
of the beds are reddish yellow. 
