Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River, in 1820 / Resumed and Completed, by the Discovery of its Origin in Itasca Lake, in 1832

by Henry Rowe Schoolcraft

2. Striped Jasper.—With the preceding. Most commonly, these specimens consist of alternate bands of red and black, or brown.

3. Red Jasper.—In quartz rock, Sugar Island, River St. Mary's, Michigan. Masses of this mineral have been met in situ.

Subs. 8.—Heliotrope.

A fine specimen of this mineral, now before me, was procured at the mouth of the Columbia River, Oregon. It is in the form of an Indian dart. Its color is a deep uniform green, variegated with small spots of red; those parts which are green being fully translucent, the others less so, or nearly opaque. This beautiful mineral is represented to have been in common use by the Indian tribes of the Northwest Coast, for pointing their arrows, previous to the introduction of iron among them. It differs chiefly from the dotted jaspers of Lake Michigan, in its translucence and green color.

Subs. 9.—Opal.

Common opal occurs as a constituent of agate, along with chalcedony rarely, in the drift on the south shore of Lake Superior.

2. Silicious Slate.

1. Common.—In subordinate beds, in the argillite of the River St. Louis, northwest of Lake Superior.

2. Basanite (Touchstone).—In detached fragments in the drift on Lake Superior, and along the banks of the Upper Mississippi generally.

3. Petrosilex.