GRAND GULF CLAYS. 07 
tash (K 2 0) ! 518 
>oda (Na 2 0) 41 .■ 
Jrown oxide of manganese (MnO) 509 
Sulphuric acid 5. 751 
!arbonic acid 1. 018 
)rganic matter and water 2. 740 
100.000 
Leaf River prairie soil, taken at the crossing of the Paulding and Brandon roads in T. 4 
I.., R. 8 E., depth 12 inches, a very clayey soil, almost jet black, crumbling readily on 
xposure after wetting: 
Analysis of clay from T. 4 N., R. 8 E. 
ilica (Si0 2 ) 63. 435 
dumina (A1 2 3 ) 16. 127 
'erric oxide (Fe 2 3 ) 6. 996 
-ime (CaO) 1. 815 
lagncsia (MgO) 1. 112 
'otash (K 2 0) 796 
oda (Na 2 0) 127 
Jrown oxide of manganese (MnO) 479 
'hosphoric acid 232 
ulphuric acid 085 
)rganic matter, water, and loss 9. 028 
100. 232 
The above analyses were made from material near the surface, which may properly be 
onsidered subsoil. However, they show the character of the underclays of the Jackson 
armation. 
CLAYS OF THE GRAND GULF GROUP (MIOCENE). 
In the Grand Gulf group there are two classes of clays, which have been described under 
he head of "Grand Gulf group," (pp. 40-44). They are the white siliceous clays interbedded 
nth the siliceous and aluminous sandstone of the northwestern district and the more 
gnitic plastic clays of the southeastern district. The entire Grand Gulf formation contains 
lore or less clays, all of which occur in stratified beds. In places these beds reach a great 
hickness. 
Stonington fire day. — At Stonington, Jefferson County, occurs a large deposit of white 
lastic clay, which, by mixing with a more sandy clay, has been used for making pressed 
rick. When used alone the white clay makes a durable fire brick. The updraft kilns of 
he brick plant at Stonington are lined with fire brick made from this clay. It is highly 
lastic and burns to a cream color. The following is an analysis of this clay: 
Analysis of Stonington fire clay, Jefferson County. 
[By W. F. Hand, State chemist.] 
ilica (SiOs) 78. 17 
dumina (AJsOs) 13 - 23 
'erric oxide (Fe 2 03) 1- 73 
ime (CaO) 28 
lagnesia (MgO) 56 
ulphur trioxide (SOa) Trace. 
loisture 1-24 
yoss on ignition 4. 08 
99.29 
Viclcsburg clay. — Five miles south of Vicksburg, on the old Roche land, a thin stratum of 
riable sandstone outcrops about 40 feet above the bed of the branch. Below the sandstone 
,ppears a bed of white friable clay which is derived from the decomposition of the sandstone. 
iome of the fragments show the sandstone in the process of change. It is very rotten and 
