66 A Last of Minerals and Organic Remains. 
long, and oneinchin diameter. They are greyish white; 
and although transparent in the fresh fracture, become 
opaque by weathering. The rock in which they occur is 
part of a trap formation which occupies the north shore of 
Lake Superior, from Iong. 87° 20’ to 91° 40’; and most 
probably farther west. I have only seen the greenstone 
porphyry of Lake Huron, as a bowlder. It differs from 
that of Gunflint Lake, in its crystals being confluent. 
Labrador Feldspar.—A fur-trading establishment of M. 
Bourassa is placed in a district of this mineral. On the 
north-east coast of Lake Huron, sixty miles west from Pen- 
etanguishine, a British naval station, and ninety miles east 
from the French River. . 
It occurs here in rock masses, constituting the islands 
and main of this intricate country. With respect to its ex- 
tent, I can only say it is five miles across, in the canoe 
route along the north shore. On its western confines it is 
divided from the great gneiss formation, stretching to the 
French River by an interval of water and woods, two miles 
broad; but on the east I clearly perceived it to graduate 
into the gneiss of the locality. My opportunities for this 
examination were remarkably good, from our having wan- 
dered thereabouts for several hours, in search af the true 
route, which we had lost. The gneiss in which it ocears 
is the same as that affording the aventurine, except that its 
stratification is better marked, and that each of the ingredi- 
ents, hornblende, feldspar, quartz and mica, are more dis- 
posed to arrange themselves in separate lamine. The mica 
is in very small quantity. ‘The more ‘common directions, 
however, here, are north-east and north; but with great 
divergencies; rendered more numerous, and even inex- 
plicable, by the broken nature. of the ground, and by the 
sweeping cycloidal curvatures common to the gneiss of this 
part of Lake Huron—each bend being from 50 to 100 
yards long. 
Entering the district of Labrador feldspar from the east, 
we first perceive the feldspar to have a remarkable lus- 
tre and transparency, to increase in quantity, and in the 
size of its facets. Soon, stratification becomes obscure—- 
and at length is indiscernible; the feldspar constituting 
nearly the whole mass. It always contains slender strings 
of greenish hornblende without any particular direction, 
