APPENDIX. 355 



2. Chlorite. 



Chlorite Slate. — la subordinate strata in the argillite of the 

 River St. Louis. 



3. Staurotide. 



In garnet-colored crystals, in detached blocks of mica-slate, in 

 the drift of Lake Huron. These crystals consist of two intersect- 

 ing six-sided prisms, truncated at both ends, forming the cross. 

 They are nearly opaque, or feebly translucent on the fractured 

 edge. 



4. Clat. 



1. Plastic Clay. — Yery extensive beds of this clay are seen 

 along the west shore of Lake Michigan,, between Sturgeon Bay 

 Portage and Chicago. Its color is generally a light blue, verging 

 sometimes into deep blue or grayish- white. It is plastic in water, 

 adheres strongly to the tongue, takes a polish from the nail, and 

 emits an argillaceous odor when moistened or breathed upon. 

 These beds of clay frequently contain iron pyrites, both in the 

 crystallized and amorphous state. 



2. Pipe Clay. — In the flats of the St. Clair and Lake George, 

 Michigan. A bed of clay, apparently answering to this descrip- 

 tion, exists at White Eiver, Lake Michigan. Its color is a gray- 

 ish-white, verging to blue. It is very unctuous and adhesive when 

 first raised, but acquires more or less of a meagre feel as it parts 

 with its moisture, drying in firm and compact masses. 



3. Variegated Clay. — On the banks of the Eiver St. Peter's, 

 Upper Mississippi. Neither the quantity in which it exists, nor 

 the precise locality is known. Its color is white, variegated with 

 stripes, spots, or clouds of red or yellow. 



4. Azure Blue Clay of St. Petards. — The locality of this substance, 

 as communicated by the Indians, is the declivity of a hill, in the 

 rear of the village of Sessitongs, one mile above the confluence of 

 the Terre Blue River with the St. Peter's. It is found near the 

 foot of this hill, between two layers of sandstone rock, in a vein 

 about fifteen inches in thickness. This vein is elevated about 

 twenty feet above the waters of the Terre Bleu, and does not ex- 

 tend far in the direction of the river. Having been resorted to 

 by the Sioux Indians a long time, a considerable excavation has 

 been made, but the supply is constant. The color of this mineral 



