206 GEOLOGICAL RECONNOISSANCE 
(2) Waterworn gravel .-.sse essence nent en ree eens 1 to 10 feet. 
(6) Rough, black, fluted sandstone, equivalent to the 
“orange sand formation” of Mississippi--++--+- 23. «« 
(c) Place of iron ore deposits ++ -++ser reer reer ence enees lto 4 “ 
(d) White cherty limestone; chert in large masses, very 
brittle and full of cracks. +--+ sere sere cere eeees 30 to 80 “ 
(ec) Light-gray limestone, mottled with flesh-colored spar, 
passing down into a light-colored calciferous sand- 
LOCK eng Dees Kee wae ee Laea eM oEa eee Rae 66 
(f) Hard compact cherty magnesian limestone, in the bed 
of Black and Eleven Point rivers,as seen at Imbo- 
boden’s ferry ene OE RT ECR eee are ee eee en 80 
(73 
258 feet. 
The grayish-buff, hard, and close textured magnesiam limestone (/f.) 
forms the bed of Black river, at Pocahontas, and Eleven Point river, at 
Mr. J. H. Imboden’s. Its thickness could not be seen at Pocahontas, but 
on Eleven Point river it is exposed to the thickness of eighty feet or more. 
(e.) is also best seen on Eleven Point river. At its base, it is a light-gray, 
calciferous sand-rock, with a sharp grit, and passes upward into a gray 
limestone, mottled with flesh-colored spar. (d.) is a rough weathering 
magnesian limestone, full of whitish chert segregated in large masses 
which are filled with cracks, and readily break into small pieces. This 
member has a variable thickness of from thirty to one hundred feet or 
more, and may be seen along the road from Pocahontas to the ferry on 
Eleven Point river. On the top of this rock is the place of the iron ore 
deposits (c.) The iron ore appears to be scattered about in patches, from 
one to four feet in depth; but it was only found extending over a limited 
area. Though sometimes mixed with too much sand, it is usually of ex- 
cellent quality, and belongs to a variety designated by mineralogists as 
“limonite.” It is usually in large cellular blocks, but occasionally pre- 
sents a globular, and concentric structure. 
The rough, ferruginous sandstone, (b.) near Pocahontas, possesses a re- 
markable, fluted structure, and was generally supposed to be manganese 
ore; but, on examination, it is found to contain only a trace of that metal. 
In the State of Mississippi, some of the slabs of this rock are so univer- 
sally, and regularly fluted that they have been used for water spouts. 
The bed (a.) composed of waterworn gravel, from one to four inches in 
diameter, belongs above the ferruginous sandstone, but is often seen, where 
that member is wanting, resting on the older rocks. It usually forms the 
capping to the highest ridges, and has a thickness of ten feet or more. 
