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

In the drift of Lake Superior. Its color is a light green and not fully translucent. It possesses a hardness and a lustre intermediate between waxy and resinous.

Subs. 5.—Chalcedony.

1. Common Chalcedony.—In globular or reniform masses imbedded in trap-rock, on the Peninsula of Keweena, Lake Superior. It is found sometimes in association with other quartz minerals. Its color is white or gray, sometimes veined or spotted with red. Also, constituting the interior lining of geodes at the rapids of Rock Island and the River Desmoines. These geodes, on breaking, often present a mammillary surface. In the form of translucent fragments, with a highly conchoidal fracture, among the debris of the shores of Lake Pepin. These fragments possess an extremely delicate texture, color, and lustre.

2. Cacholong.—Some loose fragments of this mineral exist along the west shore of Lake Michigan, between Green Bay and Chicago. These fragments possess small cavities studded over with very minute and perfect crystals of quartz.

3. Carnelian.—This mineral occurs in fragments in the debris of Lake Superior; also, in the amygdaloid; also, around the shores of the Upper Mississippi. Its color is various shades of red, or yellowish red, sometimes spotted or clouded, fully translucent, and occasionally presenting a considerable richness and beauty. Most commonly, the fragments are too small to be applied to the purposes of jewelry. Sometimes it is seen in very regular spheroidal masses, which contain a nucleus of radiated quartz. Some of the specimens would be considered as sardonyx.

4. Agate.—Is found with the preceding. It is more frequently found in larger masses, in the rock, which are sometimes spheroidal, reniform, or globular. These agates are chiefly arranged in concentric layers, which are white, red, yellow, &c., according to the colors of the different varieties of chalcedonies, carnelians, &c., of which they are composed. A close inspection would also separate them into several varieties—as onyx, agate, dotted agate, &c.

Subs. 6.—Hornstone.

In nodular or angular masses, imbedded in the secondary limestone of the west shores of Green Bay; and in the beds of argillaceous white clay strata of Cape Girardeau, of Missouri. Also, on the hills of White River, Arkansas.

Subs. 7.—Jasper.

1. Common Jasper.—In detached fragments, yellow, in the drift of Lake Superior.