THE ORES AND THEIR MODE OF OCCURRENCE. 29 



phere, retains the dark green color of the unaltered greensand. It contains 

 considerable iron pyrites and numerous casts of fossils of the Claiborne epoch. 

 This bed in turn is underlaid by a great series of sands and clays, constitut- 

 ing the Timber Belt Beds. Sometimes thin seams of iron ore are found in 

 the greensand below the main ore bed, but they are small and rarely of value. 

 At times they lie horizontally, and at others occupy joint cracks. The main 

 ore bed is usually directly overlaid by a thin seam of dark brown and very 

 hard siliceous sandstone, varying from one to six inches thick, and averaging 

 about one and a half inches. It adheres closely to the iron ore bed, though 

 the line of separation is sharp and well denned. Above this is a gray sandy 

 deposit, becoming more clayey and ferruginous towards its base, and varying 

 from one to sixty feet thick. This latter thickness is, however, very extreme, 

 and the average is about six to eight feet. As a rule the thickness of the ore 

 depends, in a general way, on the thickness of the overlying sand bed, it be- 

 ing thicker where the sand is less than fifteen or twenty feet than where it is 

 greater. Other conditions, however, enter into the thickness and continuity 

 of the iron ore bed, and these often upset the working of this rule. Never- 

 theless, the general fact holds good that when the ore is capped by a great 

 thickness of sand it is liable to be thin and discontinuous. The hills on which 

 the ore occurs are steep and show a broad flat plateau-like surface, heavily 

 capped with post oak, blackjack and hickory, generally of a small size, but 

 very dense. The ore crops out on the brinks of these hills, forming a protrud- 

 ing rim or crown, and often covering the slopes with great masses which have 

 broken off from the main bed. They are often deeply cut by the ravines of 

 creeks which have originated in springs in the superficial sand and which 

 flow away from the plateau in all directions, cutting deep gullies and expos- 

 ing the ore bed along their courses. On top of these plateau areas the cov- 

 ering of sand often conceals the ore for a distance of several miles at a time, 

 but it is always found cropping out at the top of the slopes, and in wells, 

 proving its continuity over very large areas. But, as has been stated above, 

 when the overlying sands and sandy clays reach a great thickness, the ore 

 grows thin and very often runs out altogether. 



" The following section on the slope of the plateau and just east of Gent 

 shows the occurrence of the ore: 



1. Gray or buff colored sand 1 to 10 feet. 



2. Siliceous sandstone capping 1 to 2 in. 



3. Brown laminated iron ore 2 feet. 



4. Indurated greensand with thin seams of clay and casts of fossils 45 feet. 



5. Coarse white clayey sand 20 feet. 



6. Dark blackish-brown sand, more clayey towards the base, nodules of rusty 



clay ironstone showing shrinkage cracks 31 feet. 



7. Brownish-gray sand to base of section 11 feet. 



