. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. EOCKS OF BEAVER BAY. 305 bed of Beaver River, and on the south point of Beaver Bay, is the same as that already described as showing for some miles along the coast above Beaver Bay. It is a moderately coarse, very dark-colored, and often nearly black, very highly crystalline rock, in which the three common ingredients— augite, anorthite, and titaniferous magnetite—can often be seen with the naked eye. The very dark color is due to the great abundance of the augitic ingredient, which
. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. EOCKS OF BEAVER BAY. 305 bed of Beaver River, and on the south point of Beaver Bay, is the same as that already described as showing for some miles along the coast above Beaver Bay. It is a moderately coarse, very dark-colored, and often nearly black, very highly crystalline rock, in which the three common ingredients— augite, anorthite, and titaniferous magnetite—can often be seen with the naked eye. The very dark color is due to the great abundance of the augitic ingredient, which, while commonly subordinate to the plagioclase. Fig. 18.—Sketch-map of rock exposures in the vicinity of Beaver Bay, Minnesota coast, T. 55, E. 8 E in this class of rocks, here greatly predominates. It shows all gradations between augite without foliation, and very highly foliated diallage. It is commonly quite fresh, but is also found more or less completely altered to a greenish material. It is not only the most abundant ingredient, but is also much the coarsest. Olivine is absent from some sections, and is never abundant, but when present is seen in very large areas, in which an alter- ation to a reddish-brown ocherous substance has always progressed very 20 LS. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Irving, Roland Duer, 1847-1888. Washington, Govt. Print. Off.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectgeology, bookyear1883
