476 



GEOLOGY OF CENTRAL WISCONSIN. 



On the N. W. qr, of Sec, 



Q — - 



a <« ^ := ■: 



5, T. 22, R. 6 E. (point D of map), on the west side of tlio 

 Wisconsin, kaolin occurs on the land of Mr. C. B. Gar- 

 rison. The clay here is reached about 18 inches to 23^ 

 feet below the surface, and has been exposed in places 

 for a distance of some rods, by "borrowing" for the 

 railroad near by. Several grades are to be seen. lu 

 some places the spade turns up a brilliant white article; 

 in others, for the most part nearer the surface, a kind 

 that is largely stained with the brown oxide of iron; 

 whilst at others again, the lamination of the unaltered 

 rock is still distinctly perceptible in the soft clay, in 

 which cases it is more apt to show a slight bluish cast, 

 and many sUvery mica scales. AU of the clay is quite 

 gritty from the presence of undecomposed felspar and 

 quartz grains. Rounded, reddish quartz pebbles up to 

 3^ inch in diameter, are occasionally to )je seen. Tho 

 depth of the clay at this place is said to be at times an 

 much as 4 feet. Samples of the whitest kinds yielded 

 the following results : 



807 A 807 -B S07 C 



SiUca 78.83 49.94 92.86 



Alumina 1.3.43 36.80 2.08 



Iron oxyd 74 .72 .74 



Lime 64 trace . 96 



Magnesia 07 .10 



Potash 37 ..51 .28 



Soda 07 .08 .05 



Water .5.4-5 11.62 2.-53 



99.60 99.67 99.60 



Carbonic acid 01 



Specific gravity 2.52 2. .52 





807 A is the raw clay dried at 100° C; 807 B is the 

 fine clay obtained from A by repeated stirrings and 

 v/ashings; 807 C, the coarse residue from the washing. 

 The composition of this residue is calculated from the 

 two preceding analyses. Under the microscope it is 

 seen to consist chiefly of angular fragments of quartz 

 from T5J to ^V i"ch in diameter, mingled with very fine 

 fragments of felspar. The approximation in composi- 

 tion of the roughly washed fine clay to typical kaoUnite 

 is noteworthy. The unwashed kaolin (A) is composed 

 of 32.7 fine clay (B), and 67.3 coarse residue (C). The 

 following are the compositions of B and C expressed in 

 percentages of the unwashed clay (A). The maimer of 

 distribution by washing of the various ingredients of the 



raw clay is thus indicated, and the practical advantage to be obtained by washing 



shown: 



-^ O -j-j o 

 ... G m 

 i -^ a, M 



