APPENDIX. 34:9 



2. Basanite {Touchstone). — In detached fragments in tlie drift on 

 Lake Superior, and along the banks of the Upper Mississippi 

 generally. 



3. Petrosilex. 



In large isolated masses in the bed of the Illinois River, on the 

 shallow rapids between the junction of the Fox and Yermilion 

 Rivers. It is mostly arranged in stripes or circles of white, gray, 

 yellow, &c., resembling certain jaspers, or approaching sometimes 

 to hornstone. The bed of the Illinois River, at this place, is a 

 species of gray sandstone, Also, in detached fragments, on the 

 south shore of Lake Superior, intimately mixed with prehnite. 

 In regard to the latter, Professor Dewey, of Williamstown Col- 

 lege, writes me: "I have received from Dr. Torrey, a curious 

 mixture of petrosilex and prehnite, in imperfect radiating crys- 

 tals, which was sent him by you and collected at the West. He 

 did not tell me the name, but examination showed what it was. 

 The association is singularly curious," The locality of this mineral 

 is Keweena Point, Lake Superior, 



4. Mica. 



Occurs rarely in the granite of Lake Superior. It is found in 

 place on the Huron Islands. Also, in minute folia, in the alluvial 

 soil of the Upper Mississippi. A beautiful aggregate, consisting 

 of plates of gold-yellow mica, connected with very black and 

 shining crystals of schorl, has been dug up from the alluvial soil 

 of the Island of Michilimackinac, 



5. Schorl. 



1. Common Schorl. — In crystals, in boulders of granite, at Green 

 Bay. 



2. Tourmaline. — With the preceding. 



6, Feldspar. 



As an ingredient in the granite of Huron Islands, Lake Supe- 

 rior, Also, in detached masses of granite along the west shores 

 of Lake Michigan. Also, in the form of prismatic crystals of a 

 light-green color, in the rolled masses of hornblende, porphyry, 

 greenstone, and epidotic boulders of Lakes Huron, Michigan, and 

 Superior. 



