334 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
very abundant and extraordinarily fresh olivine, anorthite, predominant 
diallagic augite, and a little titaniferous magnetite; the whole rock being in 
an unusually fresh condition. Similar occurrences obtain in several of the 
islands which lie within Nipigon Bay. 
On the south side of the sandy level belt above mentioned the sand- 
stones and red marls pass beneath the great series of diabases and amyg- 
daloids which form the southern half of the peninsula lying to the southeast 
of Black Bay. The latter rocks make up a great belt which, beginning in 
the islands about Point Magnet, takes at first a course north of northeast ; 
but at Nipigon Straits this has veered around more to the northeast. Beyond 
the straits the same belt is continued in the line of islands which lie to the 
south of Nipigon Bay, changing its course to an easterly direction in the 
Saint Ignace Island, and to south of east toward the eastern end of the 
Battle Island Group. 
Throughout this belt, which is bold in character and often makes ele- 
vations of a thousand feet or more above the lake, there is presented a con- 
stant lakeward dip of some 8°, the direction at first being southeast and 
then due south, as the middle of Saint Ignace Island is reached. According 
to Logan the rocks of which this belt is made up reach a total thickness of 
some 6,000 to 10,000 feet, consisting of amygdaloidal and non-amygdaloidal 
beds 
with intrusive masses of a more solid and a more highly crystalline character. These 
appear in general to consist of greenstone, sometimes passing into well-marked colum- 
nar basalt, and they are associated with other masses of a vitreous aspect, exhibiting 
the forms of pitchstone and pitchstone porphyry.’ 
The amygdaloidal layers are described by Logan as plainly stratified, 
as thinner than the associated crystalline beds, and as having the general 
characters of the amygdaloids of the South Shore, the usual vesicular fillings 
—calcite, quartz, agate, prehnite, epidote, copper, and various zeolites— 
occurring here also. Wrinkles indicative of a viscous flow are described as 
characterizing some beds. Dikes are said to be numerous, for the most paat 
of some kind of fine-grained, dark-colored greenstone, but also in part of a 
porphyry which “contains large crystals of feldspar disseminated through 
1 Geology of Canada, p. 71. 
