p. 99

Primitive District
109

I. So far as is at present known, all the northern portion of the Territory, extending down the Mississippi nearly to the Falls of St. Anthony, thence across to the Falls of the rivers St. Croix, Black, and Wisconsin, and thence to Lake Superior along the course of the Chocolate river in Michigan, may be considered as primitive or abounding in primitive rocks. They are mostly granite and hornblende rocks, but the other varieties of rocks belonging to this class are also found as is evidenced by the following list of the localities observed by the geologists who have visited this region. The only rock other than primitive in this district is the "Old red sandstone", one of the oldest of the transition rocks.

Red Rock Island, in the Lake of the Woods, derives its name from a red Granite rock of which it is composed. Granite is also one of the most common of the boulders scattered over the Territory. Most of the islands in that lake, and Rainy Lake, which is similar to it in general character, consist of Mica slate, the vertical layers of which are constantly decaying and falling into the water. Talzone rock island is said to be found on the Mississippi at the Little Falls; and as is the only rock in which gold occurs in the United States, it may be important to examine this locality with care.