196 
THE CLAYS OF ARKANSAS. 
Analyses of kaolins from sec. 16, T. 2 S., R. 14 W 
Silica (SiO a ) 
Alumina ( A1 2 3 ) 
Iron (ferric) oxide (Fe 2 3 ) 
Lime (CaO ) 
Magnesia (MgO) 
Potash (K 2 0) 
Soda (Na 2 0) 
Manganese (MnO) 
Water 
Water at 110°-115° C 
NW. I SE. 
45.62 
34.18 
4.05 
.20 
Faint trace. 
.53 
.54 
.17 
13.82 
99.11 
1.46 
SE. i SE. I. 
44.97 
38.87 
1.34 
.25 
Faint trace. 
.20 
.34 
Strong trace. 
14.37 
100. 34 
5.51 
The distribution of pisolitic kaolin in this district is probably 
nearly the same as that of bauxite, and the map accompanying 
Dr. C. W. Hayes's report on Arkansas bauxite a shows the distri- 
bution of bauxite and of crystalline rocks in Saline County so far 
as they are known. As in the other bauxite areas, the pisolitic 
kaolin is to be sought well below the surface, where it is probably of 
better color, softer, and freer from iron than nearer the surface. 
TERTIARY KAOLIN AT BENTON. 
Beds of kaolin that are formed by the decomposition of feldspar 
are commonly irregular and pockety in form, owing to the irregu- 
larity with which the feldspathic rocks decay. After the rocks have 
decomposed, however, the kaolin is liable to be washed away, and 
when it settles to the bottom of a body of water it will be spread 
out in horizontal beds like other sediments. It seems probable that 
some, possibly all, of the sedimentary kaolins are formed in this way. 
At Benton two beds of kaolin are associated with the Tertiary 
deposits. One of these is exposed on the north side of the stream 
in the SW. \ SW. \ sec. 36, T. 1 S., R. 15 W., on the slope of a hill 
about 600 feet northwest of Howe's pottery and at intervals along 
the face of the hill for several hundred feet. It is about 9 feet thick 
and looks like a firm white clay. Above it is 6 feet of coarse, indu- 
rated red sand, and above this is a thin sandy soil. 
The association of this bed with the pottery clays and its attractive 
appearance have led to attempts to utilize it for making the ordi- 
nary coarse pottery usually manufactured at Benton, but as it 
requires treatment different from that given the common pottery 
clays, its use for this purpose was soon abandoned. 
a Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 3, 1901, PL LXI. 
