Remarks on the Copper-mines of the State of Michigan

Abstract

The remarks contained in the following pages are the results of a general examination of the mines of Keweenau Point, made during the summer of 1865; and although the subject is not a new one, having been elaborately treated by Professor Whitney in two different works, and having received subsequent notices from Messrs. Rivot, Borie, and others, still the progress of mining enterprise has opened up some new features which have not as yet received any notice, and may be of interest to the Society. The copper-mining district of Michigan is situated in the upper peninsula, or north-western portion of that State, forming a narrow belt of country about 140 miles in length, extending in a north-easterly and easterly direction, from the boundary of the State of Wisconsin to the end of Keweenau Point, the promontory of which projects into Lake Superior on the southern shore, about midway between Fond du Lac and the outlet of the lake at Sault S. Marie. 2. Structure of the District.—The rocks of the district consist of coarse sandstones and conglomerates, occupying either shore, with a central mass of trappean rocks, which forms the mineral range proper. The sandstones on the eastern side have a south-easterly dip, while the traps, which axe well stratified, and include several conformable beds of conglomerate, together with the overlying sandstones and conglomerates of the western and northern shores of Keweenau Point, dip towards the north and north-west, or generally at right angles to the trend of the land.