100 KEMP'S ORE DEPOSITS. 



crystalline limestone with phlogopite and graphite. 5. Sandstone 

 like (1), 15 feet. 6. Crystalline limestone with beds and veins of 

 granite. E. Emmons, in the early New York Survey (Geology 

 Second District), attributed an eruptive origin to these ore bodies 

 and to the associated serpentine and limestone. Such an origin 

 is controverted by Brooks, who first recorded the lower lying sand- 

 stone. The deposits need further study. 1 



2.02.14. Example 9. Lake Superior Hematites. Bodies of 

 hematite, both red and specular, soft and hard, in metamorphic 

 rocks. They vary widely in shape, although at times quite per- 

 fectly lenticular. They are usually associated with jasper and 

 chert, and have for a footwall a relatively impervious rock of some 

 sort. Magnetite is at times present. Although of varying physical 

 structure and associations, all the Lake Superior hematites are here 

 grouped under one general example, in order to avoid unnecessary 

 subdivisons, and to emphasize their related characters. There are 

 five principal ore-producing belts or districts, which are also called 

 in instances "ranges," as they follow ranges of low hills. They 

 are, in the order of their chronological exploitation, the Marquette, 

 just south of Lake Superior, in Michigan ; the Menominee, on the 

 southern border of the Upper Peninsula and partly in Wisconsin ; 

 the Gogebic or Penokee-Gogebic, on the northwestern border be- 

 tween Michigan and Wisconsin ; the Vermilion Lake, in Minnesota, 

 northwest of Lake Superior ; and the Mesabi (Mesaba), in the same 

 general region as the last. 



2.02.15. The geology of these districts has been a subject of 

 much controversy, not alone in the relations of the separate areas, 

 but in the subdivisions of a single one. The ever-present difficulty 

 of classifying and correlating metamorphic rocks has here been 

 very great. Moreover, there are other separate districts, of re- 

 lated geological structure, which ought also to be brought into 

 harmony, and only at a very recent date has this been even par- 

 tially attained. 



2.02.16. The ores and their inclosing rocks have usually been 

 called Huronian, as this is the name formerly applied to the 



1 T. B. Brooks, "On Certain Lower Silurian Rocks in St. Lawrence 

 County, New York," Amer. Jour. Sci., iii. IV., p. 22. G. S. Colby, Jour. 

 U. S. Asso. Charcoal Iron Workers, Vol. XL, p. 263. E. Emmons, N. Y. 

 Oeol. Survey, Second District, p. 93. T. S. Hunt, "Mineralogy of the 

 Laurentian Limestones of North America," 21st Ann. Report Regents of 

 N. Y. State Univ., 1871. p. 88. J. C. Smock, Bulletin of N. Y. State Museum. 



