476 



GEOLOGY OF CENTRAL WISCONSIN. 



On the N. W. qr, of Sec. 5, T. 22, R. 6 E. (point D of map), on the west side of the 

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



g s "g rison. The clay here is reached about 18 inches to 2)-^ 



"2^ feet below the surface, and has been exposed in places 



tC-<jI 



"* for a distance of some rods, by " borrowing : ' for the 



v'z.^ railroad near by. Several grades are to be seen. lu 



Sis 3 some places the spade turns up a brilliant white article; 



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



.!? that is largely stained with the brown oxide of iron; 



g*^ whilst at others again, the lamination of the unaltered 



i z ,5 rock is still distinctly perceptible in the soft clay, in 



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



g | and many silvery mica scales. All of the clay is quite 



"8 *.2 gritty from the presence of undecomposed felspar and 



(.5 1 quartz grains. Rounded, reddish quartz pebbles up to 



^ a so i^/ inch, in diameter, are occasionally to be seen. TLo 



g<-g depth of the clay at this place is said to be at times as 



. 5 "3 much as 4 feet. Samples of the wlu'test kinds yielded 



^'3> the following results: 



807 A. 



* j|l' Silica 78.83 



JUlw Alumina.. . 13.43 



Iron oxyd 

 Lime 



Magnesia . 

 Potash... 

 Soda 



SO 7 -B 



49.94 

 36.80 

 .72 

 trace 



Water 5.45 



99.60 



Carbonic acid 01 



Specific gravity 2.52 



.51 



.08 



11.62 



99.67 



2.52 



soy c 

 92.86 

 2.08 

 .74 

 .96 

 .10 

 .28 

 .05 

 2.53 



99.60 



S>* 



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

 fine clay obtained from A by repeated stirrings and 

 washings; 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 Tfa to a V inch in diameter, mingled witli very fine 

 fragments of felspar. The approximation in composi- 

 tion of the roughly washed fine clay to typical kaolinite 

 | 7 ^ g 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 

 I percentages of the unwashed clay (A). The manner 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: 



r; a o <a 

 S.HM H 



