76 THE VERMILION IRON-BEARING DISTRICT. 



WiNCHELL, N. H. Note on the age of the rocks of the Mesabi and Vermilion 

 iron district: Eleventh Ann. Rept. Geol. and Nat. Hist. Survey Minn., for 1883, pp. 

 168-170. 



In this report the general succession of rocks in northeastern Minnesota 

 is given in descending order, as follows: (1) Potsdam, including' the Kewee- 

 nawan sandstones, shales, and conglomerates, changed by igneous gabbros 

 and dolerites locally to red quartzites, felsites, quartz-porphyries, and red 

 granites; (2) Taconic group, including the Animikie series, the Gunflint 

 beds, the Mesabi iron rocks, the Ogishke Muncie conglomerate (?), the 

 Thompson slates and quartzites, and the Vermilion iron rocks ; (3) Huronian 

 group ("?), including magnesian soft schists, becoming syenitic and porphy- 

 ritic, found on the north side of Gunflint Lake, along the international 

 boundary, at Bassvi^ood Lake, and at Vermilion Lake; (4) Montalban (f), 

 including mica-schists and micaceous granites at the outlet of Vermilion 

 Lake and on the Mississippi ; (6) Laurentian, including massive horn- 

 blende-gneiss and probably the Watab and St. Cloud granites. 



WiNCHELL, N. H. Notes of a trip across the Mesabi range to Vermilion Lake: 

 Thirteenth Ann. Rept. Geol. and Nat. Hist. Survey Minn., for 1884, 1885, pp. 20-38. 



As the result of a trip from Two Harbors to Vermilion Lake, Winchell 

 finds between these two points two rock ranges, the first being the Mesabi 

 proper, and the second the Giants range. Resting unconformably upon the 

 syenites of the Giants range are the Huronian conglomerates and greenstones 

 of Vermilion Lake, while south of this range are the slates and quartzites 

 of the Animikie, overlain by the gabbro and red granite of the Mesabi 

 range, which is in turn overlain by the trap rocks of the Cupriferous 

 series. The Huronian is considered as resting conformabh^ below the 

 Animikie, although not appearing at the surface. There are three iron-ore 

 horizons — the titanic iron of the gabbro belt, the iron ore of the Mesabi 

 range belonging in the Animikie, and the hematite of the Vermilion mines, 

 which seems to be the equivalent of the Marquette and Menominee iron ores. 



Several pages (pp. 25-35) are devoted to a description of the deposits 

 exposed by the stripping operations of the various mining companies, and 

 to analyses of the ore. 



A few details are also given concerning the distribution and subdivi- 

 sion of the crystalline rocks of Minnesota (pp. 36-38), from which we 



