20G GEOLOGICAL RECONNOISSANCE 



(a) Waterworn gravel 1 to 10 feet. 



(/;) Rough, black, fluted sandstone, equivalent to the 



" orange sand formation " of Mississippi 23 " 



(c) Place of iron ore deposit 1 to 4 " 



(d) White cherty limestone; chert in large masses, very 



brittle and full of cracks 30 to 80 " 



( ) Light-gray limestone, mottled with flesh-colored spar, 

 passing down into alight-colored calciferous sand- 

 rock 66 " 



(f) Hard compact cherty magnesian limestone, in the bed 

 of Black and Eleven Point rivers, as seen at Imbo- 

 boden's ferry 80 " 



253 feet. 



The grayish-buff, hard, and close textured magnesiam limestone (/.) 

 forms the bed of Black river, at Pocahontas, and Eleven Point river, at 

 Mr. J. II. 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. 

 (c.) 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, u^ed 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. 



