OF THE ROCKS OF LAKE SUPERIOR. 261 
the needle, although it appears to contain a large percentage of iron. Compares 
with No. 188, and similar rocks; also with No. 603 and No. 606. Weathers with 
an irregular, nodular surface. 
631. I consider this rock to belong to the metamorphosed shale-beds of Nos. 110 
and 139. It is exactly of the same structure and composition as No. 139. Colour, 
brownish red, purplish red; very compact ; fine, granular. Fracture, rather smooth, 
and disposed to be conchoidal. Has small segregations of green mineral, like that of 
No. 630. The fracture is dull; the joints incrusted with thin scales of zeolites. Be- 
longs to the “ Hat Point” series. Is very easily scratched with a knife, and shows 
no traces of a crystalline structure. _ 
632. Bears N. E. and $. W. This rock, which is related to Nos. 629 and 630, 
is semi-crystalline in structure, but appears to be a fine trap breccia; and was pro- 
bably derived from the rocks just named. Colour, reddish gray, with numerous 
green points. In the great development of zeolites in lumps and small cavities, it 
bears no little resemblance to the altered shales of Shale Bay, where they are in 
near contact with an east and west dike. It has a very irregular, rough fracture ; 
and seems to be composed, principally, of fragmentary crystals of zeolite, green 
earth, hornblende (?), and felspar (?), with a considerable percentage of iron. These 
minerals are not regularly disseminated, but occur in lumpy segregations. Numerous 
irregular, ragged cavities in some parts, lined with zeolites and green mineral. The 
red mineral is stilbite. 
633. Bears E. and W. This is the same, in all respects, as No. 629. It is 
jointed, and forms very regular three, four, and five-sided columns. Many of its 
joints are covered with a thin scale of iron-rust. At a glance, it looks somewhat 
like the N. 5° E. dikes of some localities, but a careful examination shows very 
material differences in its structure. Colour, reddish gray, with spots and stripes 
of red. Coarse granular. Weathers with a tolerably even surface of a light gray 
colour. Magnetic. In general aspect, like No. 590, but not crystalline. (See No. 
629.) In some places, shows alternate stripes of red and dark-coloured grains, the 
dark-coloured stripes being nearest the partings and joints, while the interior is red, 
with spots of green or olive-coloured soft mineral disseminated through it. This 
rock is spread over underlying beds at some places, and then the columns are per- 
pendicular, or form an angle with the horizon equal to the angle of dip. In struc- 
ture and material, may be compared with some volcanic grits. 
634. Bears E. 30° N. Colour, dark gray; fracture, irregular, and disposed to be 
lumpy. Weathers with a smooth, light gray surface. Has a crystalline appearance. 
May be compared with No. 633, except with regard to colour (this rock being free 
from the red rusty grains and bands of No. 633), and crystalline structure, the 
structure of the previous rock being granular rather than crystalline. This rock 
traverses No. 635, and may, possibly, be the dike from which No. 635, at Bitobig 
Point, was derived; the trap at that place probably resting on No. 635. This, 
however, is not certain. It must be included among the basaltic traps, more espe- 
cially as it seems to contain a mineral believed to be chrysolite. Weathers easily ; 
and on exposed surfaces, falls to small pea-like fragments, when struck with the 
hammer. These fragments are dark gray internally, and greenish black externally. 
