84 
GEOLOGY AND MINERAL RESOURCES OE MISSISSIPPI. 
TERTIARY LIMESTONE (viCKSBURG LIMESTONE). 
A narrow belt of limestone of Tertiary age crosses the State, in a direction a little north of 
west, from near Waynesboro to Vicksburg. This is the Yicksburg limestone, which is 
equivalent to the upper" part of the St. Stephen limestone of Alabama. The relations 
which exist may be indicated as follows: 
Mississippi. Alabama. 
Vicksburg limestone 1 „.„..••. ,. 
T . ' , , ^=St. Stephen limestone. 
Jackson marls and clays . J 
A very detailed description of the characters and composition of the St. Stephen lime- 
stone, as shown in its Alabama outcrop, is given by Doctor Smith on pages 77 to 81 of Bul- 
letin No. 243, while in PI. I the outcrop across Alabama and Mississippi of the St. Stephen 
and the Vicksburg- Jackson is indicated. 
In Mississippi the Vicksburg limestone usually outcrops in a low ridge that trends gen- 
erally 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 lime- 
stone. 
The Vicksburg limestone carries usually from 80 to 95 per cent of lime carbonate, with 
very little magnesium carbonate. Occasionally, however, more clayey phases are encoun- 
tered, l>nt in genera] this format ion may be everj where regarded as a possible source of Port- 
land cement material. 
The analysis below was recently made on a sample taken several miles south of Jackson, 
Hinds County: 
Analysis of Vicksburg limestone from near Jackson. 
[By <;. T. Betherington.] 
Silica (Si0 2 ) : 9. 63 
Alumina (A1 2 3 ) 2.73 
Iron oxide (Fe 2 3 ) 2.76 
Lime (CaO) 45. fli 
Magnesia (MgO) 99 
Alkalies (K 2 0, Na 2 0) '. 95 
Sulphur trioxide (S0 8 ) - 3{j 
Carbon dioxide (C0 2 ) 1 
Water J 3 '- 00 
This corresponds to a content of about SI per cent lime carbonate, and as the rock is 
otherwise satisfactory the addition of a little clay will make a suit-able Portland cement 
mixture. 
The analyses below were published in the early reports of the Mississippi geological sur- 
vey. The last two, and perhaps the other three also, were made by Dr. E. W. Hilgard. 
Analyses of Vicksburg limestones. 
1. 
2. 
3. 
4. 
5. 
Silica (Si0 2 ) 
6.30 
1 7.20 
' 48.44 
n. d. 
n. d. 
n. d. 
38.06 
n. d. 
15.05 
5. 35 
44.58 
n. d. 
n. d. 
n. d. 
35.02 
n. d. 
9.20 
6.65 
47.12 
n. d. 
n.d. 
n (1. 
37.03 
n. d. 
2. 03 
2.12 
52. 17 
Ji7 
n. d. 
n. d. 
11.53 
110 
L2.33 
Alumina (AI2O3) 
Iron oxide (Fe 2 03) 
2.70 
Lime (CaO) 
1:;. '.'■■; 
Magnesia (MgO) 
1.69 
Alkalies (K 2 0, Na 2 0) 
.79 
Sulphur trioxide (SO3) 
1.27 
Carbon dioxide (C0 2 ) 
34.72 
Water 
2. ID 
on. d.=not determined. 
1-3. Red Hills, Wayne County: Harper, Geology of Mississippi, 1857, p. 166. 
4. Brandon, Rankin County: Hilgard, Geology a 1 1 AgriouH ire of Mississippi, 1860. 
5. Byram, Hinds County: Hilgard, Geology and Agriculture of Mississippi, 1860. 
