Ochrey red oxide of iron occurs on the shores of Big Stone Lake, at the source of the St. Peter's River. A large spring rises from a level, dry plain, a few feet beyond which the mineral occurs. The Indians, who employ it as a pigment, take it up with their knives. The stratum is about eight inches thick, but just below the surface it is mixed with common earth. The spring of water is pure and unadulterated.
5. Silver.
The belief in the existence of silver ore in the region of the lakes, and particularly on Lake Superior, seems to have early prevailed. So much confidence was placed in the reports of its existence, that Henry tells when a company was formed in England for exploring the copper mines of Lake Superior (A. D. 1771), they were impelled to the search more from an expectation of the silver, which it was hoped would be found in connection with it, than from the copper.[ [234]
b. Silicious Minerals.
1. Quartz.
This interesting species being distributed in its numerous varieties throughout the region visited, I shall confine my notices to a few localities.
Subs. 1.—Common Quartz.
Occurs in the form of large water-worn masses along the shores of Lakes Huron, Michigan, and Superior. Also, in veins in the granite of Lake Superior, and in the argillite of St. Louis River. These localities all consist of the opaque varieties, with a slight degree of translucence in some places. It exists in mass at Huron Bay, Lake Superior, and in fragments of red jasper on Sugar Island, St. Mary's River.
1. Radiated Quartz.—In detached masses on the Grange, and also at the rapids of the River Desmoines, on the Upper Mississippi. At the Grange, the crystals, which are usually minute, sometimes possess a cinnamon color, or pass into a variety of crystallized ferruginous quartz.
2. Tabular Quartz.—In small, flattened masses along the shores of Lake Pepin. These masses are transparent, or only translucent. Their color is generally white, but sometimes yellow. They appear to be closely allied to chalcedony.
3. Greasy Quartz.—In detached masses along the shores of Lake Superior.