856 APPENDIX. 



substance (its distinguisliing character) is an azure copper blue of 

 more or less intensity. It is ductile and moderately adhesive, 

 when first taken up, or when moistened with water, but acquires 

 an almost stony solidity on drying. It is considerably adulterated 

 with sand or particles of quartz. It parts with its moisture ra- 

 pidly on exposure to the atmosphere, and dries without much 

 apparent diminution of volume. 



5. Qreen Clay of St. Peter's.— This differs little from the pre- 

 ceding, except in its color, which is a deep or verdigris green, ad- 

 mitting some diversity of shades. Its composition appears to be, 

 essentially, alumina, silica, carbonate of copper, water, and iron. 



6. Opivagunite; Calamet Stone; Pijje Stone. — The last of these 

 terms is a translation of the first, which is Algonquin. Under 

 these names, a peculiar kind of stone, which is much employed 

 by the Indians for pipes, has been alluded to by travellers and 

 geographers from the earliest times. It appears to be a variety 

 of argillaceous wackke. Its color is most commonly a uniform 

 dull red, resembling that of red chalk. Sometimes it is spotted 

 with brown or yeUow, but these spots are very minute, and the 

 colors usually faint. It is perfectly opaque, very compact in its 

 structure, and possessing that degree of hardness which admits 

 its being cut or scraped with a knife, or sawed without injury to 

 a common hand-saw, when first raised from the quarry; but it 

 acquires hardness by exposure, and even takes a polish. But it is 

 not capable of receiving a polish by the usual process of rubbing 

 with grit-stone and pumice, these substances being too harsh for 

 it. The Indian process is to scrape or file it smooth, and give it 

 a polish by rubbing with the scouring rush. Its powder is a light 

 red, and emits an argillaceous odor when wetted. This substance 

 is procured at the Coteau des Prairie, intermediate between the 

 sources of the St. Peter's and the Great Sioux Elvers. Some other 

 places have been mentioned as affording this mineral, particularly 

 a locality on the waters of Chippewa Eiver ; but the mineral pro- 

 cured here is chocolate-colored. 



e. Magnesian Minerals. 

 1. Serpentine. 



At Presque Isle Point, Lake Superior, common and precious, in 

 isolated masses; also, in connection with, and imbedding native 



