. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. THE BEAVER BAT GEOUP. 311 shows a rock composed chiefly of clouded orthoclase and oligoclase, and large quartz areas. A few clusters of rounded particles of augite are seen. The augite is older than the feldspars and the feldspars older than the quartz. The latter ingredient does not saturate the feldspars after the usual manner of secondary quartz, but molds itself around them or invades them in large areas, or even includes broken pieces of feldspars. At B, of Fig. 20, the rock is
. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. THE BEAVER BAT GEOUP. 311 shows a rock composed chiefly of clouded orthoclase and oligoclase, and large quartz areas. A few clusters of rounded particles of augite are seen. The augite is older than the feldspars and the feldspars older than the quartz. The latter ingredient does not saturate the feldspars after the usual manner of secondary quartz, but molds itself around them or invades them in large areas, or even includes broken pieces of feldspars. At B, of Fig. 20, the rock is a fine-grained, brownish-black, conchoid- ally fracturing diabase of the ordinary type, with chlorite and quartz pseud- amygdules, rising in a low ledge above the shingle of the beach. Expos- ures C C, also low, are of the same kind of rock, mingled with which are seams and patches of brick-red felsite, the black and red presenting the appearance of having been in a semi-fused condition together. The red felsite in the thin section shows a red matrix, saturated with exceedingly thin fibers of secondary quartz arranged in sheaf-like bundles. Quite large quartz areas are also contained, which are not single individuals as in the quartzes of a quartz-porphyry. It is possibly only a phase of the pink rock of the south wall of the bay. Beyond the point C there are 80 paces of a beach without ledge, be- yond which again rises the north wall of the bay, D E. This wall is composed as indicated in the following figure. The west part of the wall is made up. Fig. 21.—Section of wall DE of Fig. 20. of plainly bedded fine-grained diabase, laumontitic amygdaloid, and luster- mottled melaphyr. These are terminated by a narrow ravine 15 feet wide and 100 feet deep, the east face of which is made up of the pink felsite which forms the rest of the point. This face is beautifully slicken-sided, being polished in some places to a glassy surface, and marked from top to. Please note that these im
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectgeology, bookyear1883
