340 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
On the west shore of the lake sandstone is said to occur interstratified 
with beds of “‘argillite,” felsite,” and ‘“ trap,” 
all on edge, and running in a northerly direction. * * * Some of the felsite beds are 
soft greenish and earthy; others harder and schistose. The argillite is hard dark col- 
ored and compact, with a conchoidal fracture; while the sandstones are light-colored 
and soft. One bed of the latter, of a very light greenish-gray color, is composed of fine 
silicious and argillaceous particles, with scattered grains of translucent quartz. [At 
another point farther up the west shore there shows under high cliffs of trap] a band 
of light-gray tender harsh-grained sandstones, about 100 feet thick, dipping 8S. 80° W. 
(mag.) <50°, which appears to come between great masses of coarse crystalline trap. 
Two miles farther south, or about a quarter of a mile north of the extremity of Black 
Sturgeon Lake, beds of a coarse light-gray sandstone, holding occasional pebbles, mostly 
of white quartz, are found lying against the side of a bill of gray splintery schistose 
felsite. The sandstone dips southwestward at an angle of about 40°, while the felsite 
dips in the opposite direction, with an inclination of about 60°." 
The limestones were seen in two places, one on the south side of Lake 
Nipigon and one on the west. In the former case the limestone is— 
thinly bedded, and consists of alternating whitish and olive-green layers. The rock, 
which has a fine homogeneous texture and conchoidal fracture, is magnesian and ar- 
gillaceous, and when burnt would probably form a good cement. Some indistinct 
forms, resembling fossils, occur in it, but nothing definitely organic was observed. The 
limestone band is generally horizontal, but in some places it is thrown into a series of 
small anticlinals, having their axes north and south. It is overlaid by the trap, which 
rises to a height of about 100 feet immediately above it.” 
The limestone of the west shore shows on the north side of the 
Narrows at the mouth of Chief’s Bay.2 Here— 
trap is overlaid by compact argillaceous magnesian limestone, with a conchoidal frac- 
ture, dipping S. 25° W. (mag.) <5°. The beds are from three inches to two feet and a 
half in thickness, and present different shades of a grayish and olive-green color. 
Although the section exposed does not appear to exceed ten feet in thickness, so regu- 
lar and slight is the dip that these rocks extend for a quarter of a mile along the shore, 
and are seen along a brook to the northwestward and in the bottom of the lake in front. 
Small pear-shaped bodies, about the size ofspeas, weather out on the surfaces-of some 
of the beds, but they show no organic structure, either outwardly or in sections exam- 
ined under the microscope. The same olive-green limestone occurs again on the north- 
east shore of Chief’s Bay, about two miles from the Narrows. The beds are from six 
inches to two feet thick, and dip S. 40° W.(mag.) <8°. A section of six or eight feet 
is exposed, and the strata are underlaid conformably by beds of fine-grained compact 
black trap, showing crack-marks on the surface.* 
1 Op. cit., p. 345. 2 Op. cit., p. 342. 
%See map accompanying Bell’s report in Report of Progress of the Geological Survey of Canada 
for 1867-69. 
4Op. cit., p. 346. 
