218 CEMENT MATERIALS AND INDUSTRY. [bull. 243J 
Eutaw sands extend west of the town of Aberdeen for 2 miles. 
Here the post-oak lands begin, and the regular prairie soils one-half 
mile farther west. There are no outcrops of Selma from Aberdeen 1 if 
to Prairie Station. The first outcrop found northwest of Aberdeen is 
at Strongs. Outcrops of Selma here, as farther south, are very fe\^ 
on the east edge of Selma. 
The following analysis of a sample of the Selma chalk from near 
Okolona, Chickasaw County, Miss., is an old one, made by Doctor \ 
Hilgard/' Of the material reported as "insoluble," probably about 
two-thirds was silica, the remainder being alumina and iron oxide. 
Analysis of limestone from Okolona, Miss. 
Insoluble (mostly silica, Si0 2 ) 10. 90[i 
Alumina ( A1 2 3 ) 1. 9 
Iron oxide (Fe 2 3 ) 1. 42 \ 
Lime ( CaO) *> 45. 79 I 
Magnesia ( MgO) c . 88 s 
Alkalies (K,0, Na 2 ( ) ) 57 
Carbon dioxide (C0 2 ) 35. 73 
Water and organic 2 
TERTIARY LIMESTONES (VICKSBURG LIMESTONE). 
A narrow belt of limestone of Tertiary age crosses the State in ai 
direction a little north of west, from near Waynesboro to Vicksburg. 
This is the Vicksburg limestone, which is equivalent to the uppen 
part of the St. Stephens limestone of Alabama. The relations which | 
exist may be indicated as follows: 
Mississippi. Alabama. 
Vicksburg limestone 
f — St. Stephens limestone. 
Jackson marls and clays. ' 
A very detailed description of the characters and composition of the 
St. Stephens limestone, as shown in its Alabama outcrop, is given b$ 
Doctor Smith on pages 77 to 81 of this bulletin, while on PI. II the ' 
outcrop across Alabama and Mississippi of the St. Stephens and the 
Vicksburg-Jackson is indicated. 
In Mississippi the Vicksburg limestone usually outcrops in a lowv 
ridge that trends generally a little north of west. The southern slope 
of this ridge is gentle, but its northern face is a sharp declivity, which > 
makes it easy both to locate the outcrop and to quarry the limestone 
The Vicksburg limestone carries usually from 80 to 95 per cent off 
lime carbonate, with very little magnesium carbonate. Occasionally, 
however, more clayey phases are encountered, but in general this 
formation may be everywhere regarded as a possible source of Port- 
land cement material. 
a Report on the Geology of Mississippi, p. 101. 1860. 
b Equals lime carbonate (CaC0 3 ), 81. 77. 
c Equals magnesium carbonate (MgC0 3 ), 1.84. 
