The views herein expressed are generalized in two geological maps (hereto prefixed), which, it is believed, will help to fix the facts in the mind. They exhibit the facts noticed, in connection with the theory established by them, and by all my observations, of the construction of this part of the continent.
The mineralogy of the regions visited is condensed in the following summary, drawn from my notes, which, it is believed, constitutes an appropriate conclusion to this report.
With the exception of one species, namely, the ores of copper, the region has not proved as attractive in this department as I found the metalliferous surface of Missouri. There are but few traces of mining, and those of an exceedingly ancient character, in the copper region of Lake Superior. The excavations in search of lead ore on the Upper Mississippi do not date back many years, but the indications are such as to show that few countries, even Missouri, exceed them in promises of mineral wealth.
I have employed the lapse of time between the termination of the exploration and the present moment, to extend my mineralogical observations to some parts of the Mississippi Valley which were not included in the line of the expedition, but which were visited in the following year, in the service of the Government, namely, the Miami of the Lakes, and Wabash Valleys, the Cave in Rock Region in Lower Illinois, and the Valley of the River Illinois. The whole is concentrated in the following notices:—
Tabular View of Minerals observed in the Northwest.
| I. ORES. | ||||
|---|---|---|---|---|
| Genera. | Species. | Subspecies. | Varieties. | |
| Metallic minerals | Copper | Native copper. | ||
| Green carbonate of copper | Fibrous. | |||
| Compact. | ||||
| Lead | Sulphuret of lead | Common. | ||
| Zinc | Sulphuret of zinc | Blende. | ||
| Iron | Sulphuret of iron | Common. | ||
| Radiated. | ||||
| Spheroidal. | ||||
| Cellular. | ||||
| Hepatie. | ||||
| Magnetic oxide of iron | Iron sand. | |||
| Specular oxide of iron. | Micaceous. | |||
| Red oxide of iron | Ochrey. | |||
| Scaly. | ||||
| Compact. | ||||
| Brown oxide of iron | Ochrey. | |||
| Silver. | ||||
a. Metallic Minerals.
1. Copper.
This metal is frequently found, in detached masses, in the diluvial soil along the southern shore of Lake Superior, and in the high and barren tract included between Lakes Huron, Michigan, and Superior, and the Mississippi River, as general boundaries. Thus, it has been found upon the sources of the Menomonie, Wisconsin, Chippewa, St. Croix, and Ontonagon Rivers, but most constantly, and in the greatest quantity, upon the latter. There are many localities known only to the aborigines, who appear to set some value upon it, and have been in the habit of employing the most malleable pieces in several ways from the earliest times. It occurs mostly in detached masses, resting upon, or imbedded in, diluvial soil. These masses, which vary in size, are sometimes connected with isolated fragments of rock. Such is the geognostic position of the great mass of native copper upon the banks of the Ontonagon, which has been variously estimated to weigh from two to five tons. This extraordinary mass is situated at the base of a diluvial precipice composed of reddish loam and mixed boulders and pebbles of granite, greenstone, quartz, and sandstone and diallage rocks. The nearest strata, in situ, are red sandstone, grauwacke, and greenstone trap. A company of miners was formerly employed in searching for copper mines upon the banks of this river. They dug down about forty feet into the diluvial soil, at a spot where a green-colored water issued from the hill. In sinking this pit, several masses of native copper were found, and they discovered, as their report indicates, the same metal "imbedded in stone." But the enterprise was abandoned, in consequence of the falling in of the pit.