from Northeastern Minnesota. 177 



found in Michigan have been called anthophyllite schists by 

 Brooks and Brush* and by Julien.f In the Penokee district 

 of Michigan and Wisconsin, Irving and Yan Hise:}: describe 

 them as actinolitic and magnetitic slates, and mention them as 

 forming a portion of the iron-bearing member, just below the 

 upper fragmental slates and immediately above the similarly 

 fragmental vitreous quartzites of the Penokee series. They 

 are associated with slaty and cherty iron carbonates and with 

 ferruginous slates and cherts, regarded as chemical sediments. 



Lane and Sharpless§ have recently shown that in some of 

 these schists from the Marquette area the amphibole is rich in 

 iron and magnesium, while entirely devoid of even a trace of 

 calcium, and hence that it should be classed with the variety 

 grunerite. 



The relations of these schists to the other members of the 

 iron-bearing series have been made out only in the Penokee 

 area as above stated, though they are said by Irving and Yan 

 Hise|| to be intimately associated with cherty carbonates in the 

 Animikie rocks of Minnesota. 



The widespread occurrence of these peculiar rocks through- 

 out all of the iron-bearing horizons of the Lake Superior 

 region that have been subjected to more than a merely super- 

 ficial examination, must be of significance. Consequently the 

 discovery of them on the newly opened Mesabe Ranged is of 

 some interest from a theoretical, if not from a practical stand- 

 point. The object of this note is simply to announce this 

 discovery and to describe very briefly the characteristics of the 

 rocks. 



The easternmost end of the Mesabe area is in the vicinity of 

 T. 6m . R . 12 W. Minnesota. In the S.E. J of the S.E. \ of 

 Sec. 34 in this town, and only half a mile from the north side 

 of the gceat gabbro mass lying to the south, is a series of dark, 

 heavy schists highly charged with magnetite. Of these eight 

 specimens have been examined, the geological associates of 

 which are unfortunately not known. Under the microscope it 

 is seen that these rocks consist almost exclusively of magnetite 

 and an almost colorless amphibole. 



The magnetite forms from fifty to ninety per cent of the 

 entire rock-mass. It occurs as large and small grains imbedded 



* T. B. Brooks and G. J. Brush: Geological Survey of Michigan, vol. i, 1869- 

 1873, p. 114. 



f A. A. Julien:*Ib.. vol. ii, 1873. p. 24, 91-93, etc. 



i R. D. Irving and C. R. Van Hise: The Penokee Iron-bearing Series of Michi- 

 gan and Wisconsin, 10th An. Rep. U. S. Geol. Survey, p. 389. 



§ A. C. Lane and F. F. Sharpless : this Journal, xlii, p. 505, 1891. 



|| R. D. Irving and C. R. Van Hise, 1. c, p. 404. 



*~ H. V. Winchell : The Mesabe Iron Range, Geol. and Nat. Hist. Survey of 

 Minn., 20th Ann. Rep., p. 111. 



Am. Jour. Sol— Third Series, Yol. XLYI, No. 273.— Sept., 1893. 

 13 



