. The Crystal Falls iron-bearing district of Michigan. Iron ores; Geology; Geology, Stratigraphic; Geology, Stratigraphic. ORE DEPOSITS OF UPPER HURON IAN. 177 DRILL HEMLOCK 87°. Tlu' si'vero dotoniiatiou is olcarly shown l)ytlu' plication of the beds, and by faults whose extent can not be determined, but which are accom- panied by rather extensive reiljuugsbreccias. The breccias are cemented b\- iron oxide. THE AMASA AREA. The Aniasa deposits must of necessity be very briefly described, as I have l)een unable to obtain much information concerning the relations of the rocks as shown in the clo
. The Crystal Falls iron-bearing district of Michigan. Iron ores; Geology; Geology, Stratigraphic; Geology, Stratigraphic. ORE DEPOSITS OF UPPER HURON IAN. 177 DRILL HEMLOCK 87°. Tlu' si'vero dotoniiatiou is olcarly shown l)ytlu' plication of the beds, and by faults whose extent can not be determined, but which are accom- panied by rather extensive reiljuugsbreccias. The breccias are cemented b\- iron oxide. THE AMASA AREA. The Aniasa deposits must of necessity be very briefly described, as I have l)een unable to obtain much information concerning the relations of the rocks as shown in the closed mine. In the early days of the mine it was thought by the mine captain that the volcanics fonned the foot wall of the ore, and on liis authority Van Hise says, "The ore of the Hemlock mine rests upon a stratum consisting of surface volcanic mate- rial " ^ ^"^' ^^'—'^^***^^® section illustrating results of diamond-drill work. Probably this is a mistake, for the section from west to east (fig. 11), i. e., from the higher to the lower beds, obtained in two drill holes, is as follows: Feet. Gray sericitic ulate, discolored liy iron 115 Chert and jasper 59 Pyritiferous black slate aud quartzito 180 Ore formation .* 3q^ Magnetitie slate 40 Mottled slates, red and green, containing iron. Drilling ceased after passing through 70 The thickness of the beds given is the true one and not the thickness passed through by the drill, which cut through the beds at an angle. These beds projected to the surface are found to be immediately underlain by greenstone, in some places massive, in others tufaceous. Moreover, an identical section is shown by a drill hole 4 miles southeast of Amasa, in sec. 26, T. 44 N., R. 33 W. It was carried deeper, however, and after passing through the mottled slate was bottomed in greenstone. From these drill. LOWER huroniaN The iron ores of the Marquette district of Michigan, by C. R. Van Hise; Am. Jour. Sci., vol. 43, 1892, p. 130. MON XXXVI
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