. The Vermilion iron-bearing district of Minnesota : with an atlas . nd but for the presence of the elongated ellipsoids and theamvgdules, filled with chlorite and pinkish quartz, one could not be sure,from the field study, of theii- igneous origin. The rocks in this localityresemble in a striking degree the crystalline schists occurring in thevicinity of Bone Lake, in the Crystal Falls district of Michigan. It has been stated repeatedly that certain of the greenstones possessan amygdaloidal structure, and that with these tuffs are associated. Thesefacts have been cited as evidence of the volc
. The Vermilion iron-bearing district of Minnesota : with an atlas . nd but for the presence of the elongated ellipsoids and theamvgdules, filled with chlorite and pinkish quartz, one could not be sure,from the field study, of theii- igneous origin. The rocks in this localityresemble in a striking degree the crystalline schists occurring in thevicinity of Bone Lake, in the Crystal Falls district of Michigan. It has been stated repeatedly that certain of the greenstones possessan amygdaloidal structure, and that with these tuffs are associated. Thesefacts have been cited as evidence of the volcanic nature of the associated and presumably interbedded tuifs and amygdaloidal andporphyritic greenstones are very well exposed upon the west and north-west slopes of a high hill in the northwest quarter of sec. 19, T. 64 N.,R. 10 W. Here tlie greenstones, which are both fine and coarse grained, The Crystal Falls ?iron-bearing district of Michigan: Mon. U. S. Geol. Survey Vol. XXXVI,1899, pp. 148-152. U. S. GEOLOGICAL SURVEY MONOGRAPH XLV PL. V. m;
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