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

23. Stilbite. Amygdaloid rock, Keweena Point, Lake Superior.

24. Zeolite. Mealy. With the preceding.

25. Zeolite. Radiated. Lake Superior. This mineral consists of fibres, so delicate and firmly united as to appear almost compact, radiating from a centre. Some of the masses produced by this radiation measure 2.5 inches in diameter. They are of a uniform, pale, yellowish red. This mineral has not been traced in sitû, being found in detached masses of rock, and sometimes as water-worn portions of radii. Its true position would seem to be the trap-rock.

26. Asbestus. Presque Isle, Lake Superior. In the serpentine formation.

27. Hornblende. Very abundant as a constituent of the primitive rocks on the Upper Mississippi, and in the basin of Lake Superior. Often in distinct crystals.

28. Diallage, green. Lake Superior. In detached masses, connected with primitive boulders. Harder than the species.

29. Serpentine, common. Presque Isle, Lake Superior.

30. Serpentine, precious. With the preceding. Color, a light pistachio green, and takes a fine polish. Exists in veins in the common variety.

31. Pseudomorphous serpentine. With the preceding. This beautiful green mineral constitutes a portion of the veins of the precious serpentine. Its crystalline impressions are very distinct.

32. Argillite. River St. Louis, northwest of Lake Superior. Nearly vertical in its position.