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The ore bodies are found in beds of banded lean jasper, which is always an invariable associate of the richer ore, and it may occur anywhere within the jaspery horizon. The rich ore often appears to be a part and parcel of the general stratification of the lean ore encompassing it. Not infrequently one finds spots which are apparently in the transition state from the lean jaspery ore, as though the ore body was charged with a solution, which was gradully dissolving out the silica from the adjacent jasper. There is invariably a notable pitch to the ore bodies, and it is generally to the west at an angle of from 30° to 50°. Connected with some of the ore bodies are well defined hanging or foot-walls of so-called soapstone, but often when there are no well-defined walls, the ore body being found in the jasper, the ore is quite sure to carry a minimum of phosphorus, as exemplified at the Millie, Pewabic, Cyclops, Aragon, and S. E. Vulcan mines. The productive portions of the range appear to be located at the points where the formation has been faulted, eroded deeply, or sharply folded.

Comments.—The sections give additional evidence that in the Menominee district, as in the Marquette, there are two unconformable series. The Chapin, Ludington, and Hamilton appear to belong to the Lower Huronian. The horizon of quartzite, slate and conglomerate is evidently the basal conglomerate of the Upper Huronian. The Mille, Pewabic, and similar ore bodies, are in the Upper Huronian. That the ore bodies occur in disturbed areas, and frequently rest upon soapstone or other impervious formations, accords perfectly with what has been previously ascertained as to the manner of concentration of the Lake Superior iron ores.

Van Hise^[1] gives the following as the ascending succession in the iron-producing part of the Marquette district: (1) Basement Complex, consisting of granites, gneisses, schists, and greenstone-conglomerates, the whole intricately intermingled, and the schists intruded by the granites and gneissoid granites; unconformity: (2) Lower Marquette series, having at its base a conglomerate and quartzite formation, upon which rests an iron-bearing formation; unconformity; Upper Marquette series, which looked at broadly is a great shale, mica-slate and mica-schist formation, but it often has at its base quartzites and conglomerates, and several hundred or a thousand feet from its base an iron-bearing formation similar to that of the Lower Marquette series. Included within both the Lower and Upper Marquette series are many basic intrusive dikes and bosses of diabase, and also contemporaneous volcanics, which are largely tufaceous.

At the east end of the Marquette district is the Mesnard series, the position of which has not as yet been determined.