824 APPENDIX. 



pliiboles, and a variety of masses in whicli epidote and horn- 

 blende are essential constituents. With these, the coast mineral- 

 ogist mnst associate, in place or out of place, agates, chalcedonies, 

 carnelians, zeolite, prehnite, calcareous spar, crystalline quartz, 

 amethystine quartz, coarse jaspers, noble serpentine, iron-sand, 

 iron-glance, sulphate of lead, chromate of iron, native copper, 

 carbonate of copper, and various species of pyrites. These were, 

 at least, my principal rewards for about eighteen days' labor, in 

 scrutinizing, at every possible point, its lengthened and varied 

 coasts. 



Cupreous Fokmation, — The whole region, above Grand Is- 

 land at least, appears to have been the theatre of trap-dykes, and 

 an extensive action from beneath, which brought to the surface 

 the elements of the formation of copper veins. These have not 

 been much explored ; but, so far as observation goes, there are 

 evidences which cannot be resisted, that the region contains this 

 metal in various shapes and great abundance. I refer to my re- 

 port of the 6th of November, 1820, for evidences of a valuable 

 deposit of this metal in the valley of the Ontonagon River, and at 

 other points, I found the metal in its native state at various 

 other localities, and always under physical evidences which de- 

 noted its existence, in the geological column of the lake, in quan- 

 tity. These indications were confined almost exclusively to the 

 area intervening between the peninsula of Keweena, and La 

 Pointe Chegoimegon, a distance of about one hundred and fifty 

 miles. Of this district, the two extremities would make the On- 

 tonagon Valley about the centre,* A profile of one of the de- 

 tached pieces, found in the Ontonagon Valley, and forwarded to 

 you by Mr, Van Rensselaer, is herewith given, 



ViTRic Boulders, — Among the debris of Lake Superior are 

 masses of trachyte, and also small pieces of the sienitic series, 

 in which the red feldspar has a calcined appearance, the quartz 

 being, at the same time, converted into a perfectly vitreous 

 texture. Similar productions, but not of the same exact charac- 

 ter, exist on the sandy summits of the Grande Sable. These 



* I would also refer, for subsequent information, to my report of the 1st of Oc- 

 tober, 1822, made in compliance to a resolution of the Senate, and printed in the 

 Executiye Documents of that year, No. 365, 17th Congress, 2d session. 



