MINERAL RESOURCES. 89 
The lignite is overlain by a bed of gray clay and this by stratified red, yellow, and white 
sand, with occasional beds of ferruginous sandstone in the sand. On these hills there is a 
deposit of Lafayette that reaches in places a thickness of 20 feet, and in this there is con- 
siderable ferruginous sandstone. 
One of the distinguishing features between the Tertiary lignites of Mississippi and the true 
coals of the Carboniferous is in the mode of occurrence. True coals are almost always over- 
lain by beds of compact shale which forms a '"roof" over the coal. The roof is of great 
service in timbering the mine. In the Tertiary lignites the roof of shale is always wanting. 
Thin bands of ferruginous sandstone overlying the lignite seams are often mistaken for the 
true roof. 
OCHEK. 
A beautiful red ocher underlying a large area east of Iuka, Tishomingo County, deserves 
special mention. It occurs in large bodies very similar to the white-clay deposits. It is of 
a pale-scarlet color, with small dark-brown specks of vegetable matter which has not changed 
as much as the main body; small particles of white clay also appear through it. The best 
exposures are found on R. F. Thome's land, 6 miles northeast of Iuka, where it was formerly 
obtained and shipped for making paint, but this body has for some cause been abandoned. 
Other outcrops occur on Mr. Moore's place, 2 miles east-southeast of Iuka, and at LakeComo, 
just outside the town. 
PHOSPHATES, GREENSxVNDS, MARLS, AND OTHER FERTILIZERS. 
Natural fertilizers occur in widely separated formations of the State. Despite the exhaus- 
tive treatise on the marls, greensands, and clays by Hilgarda little attention seems to have 
been paid to these means of improving the productiveness of the soils by the farmers of the 
State. Many of the cold and exhausted soils could be greatly improved and much better 
crops realized by the application of these natural fertilizers. 
The upper portion of the Tuscaloosa and the lower portion of the Selma formations are 
highly impregnated with greensand, which contains more or less carbonate of lime and 
potash. Where these formations come to the surface they form a belt of very productive 
country. These greensands might be profitably used as a dressing on the exhausted lands 
of the Selma chalk area farther west, where there is still a large amount of carbonate of lime, 
but a lack of potash. 
In the upper Cretaceous, particularly in the Ripley, the marls contain an average of 15 
per cent of carbonate of lime and from one-half to 1 per cent of potash. The limestones of 
the Midway are likewise very rich in potash. 
Greensand occurs in greater or less quantities throughout the Tertiary. Its presence is 
detected by the added fertility of the soil. In the Claiborne, Jackson, and Vicksburg forma- 
tions it is present in the calcareous clays, marls, and limestones. These marls will be of 
great value if applied on the thin clay or loamy soils of central and southern Mississippi. 
aHilgard, E. W., Geology and Agriculture of Mississippi, 1860. 
