292 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
tained in the eruptive rocks, was noted on the shore near the east line of 
See. 1, T. 53, R. 10 E. Here the shore cliff for some distance is a black 
rock, coarser than the most of the massive rocks of the Agate Bay Group. 
This rock contains angular masses of a very coarse white-weathering an- 
orthite-rock, of all sizes from fragments a few inches across to others three 
or four feet in length. These masses are irregularly and never abundantly 
distributed. The appearance is like what is often met with in the overlying 
or Beaver Bay Group of beds, and is further described in connection with 
that group. 
The sandstone layers observed in the Agate Bay Group are all very 
thin, never exceeding three or four feet in thickness. They were met with 
at five different points along the coast between Lester and Gooseberry 
rivers, and probably at three different horizons. About three miles below 
Lester River, on Sec. 34, T. 51, R. 13 W., large water-worn surfaces of 
one of the dense, hard, brown, laumontitic amygdaloids, above described as 
characterizing the lower portions of the Agate Bay Group, are seen to be 
traversed by intersecting seams of bright-red sandstone, from a fraction of 
an inch to several inches in width Besides the larger areas of amygda- 
loid contained by the intersecting sandstone seams, there are smaller pieces 
completely surrounded by the sandstone of one seam. Fig. 13 represents 
these intersecting seams as 
seen in an area 20 by 10 feet. 
» The sandstone of these seams 
is fine-grained, dark-reddish 
and argillaceous. The thin 
section shows it to be wholly 
fragmental, and to be com- - 
> posed of minute particles of 
Fic. 13.—Sandstone ‘‘ veins,” Minnesota coast—plan. 
quartz with other porphyry 
detritus, together with here and there dark-colored particles and particles 
of triclinic feldspar which probably are from some of the basic eruptives. 
When first seen these apparent veins of sandstone showed no connection 
with any other sandstone, but a few rods farther down the coast the amyg- 
daloid in which they occur was found overlain by the remnant of a thin 
