7(1 THE GEOLOGY OF MINNESOTA. 



[Nicolkt, 1838. 



The principal rock that strikes the attention of the observer in this remarkable inland bluff, 

 is an indurated (metamorphic) sandrock, or quartzyte, the red color of which diminishes in 

 intensity from the base to the summit. It is distinctly stratified; the upper beds being very much 

 weather-worn and disintegrated into large and small cubic fragments. 



The whole thickness of this quartzyte, which immediately overlies the bed of the red pipe- 

 stone is 26i feet. Its strata appear to have a small dip to the N. E. The floor of the valley, 

 which is higher than the red pipestone, is formed by the inferior strata of the quartzyte, and in 

 the spring of the year is most generally under water; the action of which upon the rock is apparent 

 in the great quantity of fragments strewed over the valley, so as to render it uncomfortable to 

 walk over them. The creek by which the valley is drained, feeds in its course three distinct small 

 basins at different elevations, that penetrate down as far as the red pipestone. 



This red pipestone, not more interesting to the Indian than it is to the man of science, by its 

 unique character, deserves a particular description. In the quarry of it which I had opened, the 

 thickness of the bed is one foot and a half ; the upper portion of which separates in thin slabs, 

 whilst the lower ones are more compact. As a mineralogical species it may be described as fol- 

 lows: compact; structure slaty; receiving a dull polish; having a red streak; color blood-red, 

 with dots of a fainter shade of the same color ; fracture rough ; sectile ; feel somewhat greasy; 

 hardness not yielding to the nail ; not scratched by selenite, but easily by calcareous spar ; specific 

 gravity 2.90. The acids have no action upon it ; before the blowpipe it is infusible per se, but 

 with borax gives a green glass. 



According to Prof. Jackson, of Boston, who has analyzed and applied to it the name of 

 catlinite, after Mr. Catlin, it is composed of 



Water 8.4 



Silica 48.2 



Alumina 28.2 



Magnesia 6.0 



Peroxide of iron 5.0 



Oxide of Manganese 0.6 



Carbonate of lime 2.6 



Loss (probably magnesia) 1.0 



Total : 100.0 



But Prof. Jackson assimilates it to the agalmatolite, from which it differs, however, very 

 materially by its general aspect, its conduct before the blowpipe, and its total insolubility in sul- 

 phuric acid.* 



Another feature of the Bed Pipestone valley is the occurrence of granitic boulders of larger 

 size than any I had previously met. One of these measured about sixty feet in circumference, 

 and was from ten to twelve feet thick. They are strewed over the valley, in which it is remark- 

 able that there are no pebbles. 



The name of Mr. Nicollet, and the initials of his companions, are hand- 

 somely cut in the hard quartzyte at the top of the ledge near the Leaping 

 Rock, a little north of where the creek passes over the brow of the escarp- 

 ment, as here represented and arranged, viz : 



J. N. Nicollet. 

 C. F. &JJ1 

 C. A. G. * -g 



J. L. oo 2: 



J. E.F. 5| 

 J. R. 



*The red pipestone in also found on the upper part of the Mishkwagokag, or Red Cedar river, which falls into the 

 Chippeway river that empties itself into the Mississippi river below lake Pcpin. 



