. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 292 COPPER-BEARING ROOKS OF LAKE SUPERIOR. tained in the eruptive rocks, was noted on the shore near the east line of Sec. 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 abundantl
. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 292 COPPER-BEARING ROOKS OF LAKE SUPERIOR. tained in the eruptive rocks, was noted on the shore near the east line of Sec. 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 rivei-s, 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 .i/j, t. A-^ â ':-J^^^^^^^^^^^:^I-'^,-?'-^^V^^JW?:> seen m an area 20 by 10 feet. ^^^>^^^'M^>^^i^^^^^^'^W9^^W^M'> The sandstone of these seams â .). o'^ is fine-grained, dark-reddish ^tiM^.;s^^^^g,^ti^c^s^cdlh^^'^:^ posed of minute particles of Fig. "veins," Minnesota coast-plan. quartz with Other porphyry detritus, together with here and there dark-colored parti
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectgeology, bookyear1883
