130 GEOLOGICAL RECONNOISSANCE 



geological corps, north of the Arkansas river : i. e., in the part of the State 

 on which I am noiv reporting. 



Arkansas is destined, I believe, to take the lead of all the Western 

 States, in her resources in ores of zinc and manganese. 



The magnesian limestone, belonging to the lower Silurian period, seems 

 to be the great repository of the zinc ore, of which there are three princi- 

 pal varieties : the pure carbonate of zinc — the calamine or smithsonite of 

 mineralogists — the silicate of zinc or electric calamine — and the sulphuret 

 of zinc or blende (black-jack of the miner). 



The analyses of these ores prove them to be at least as rich as, if not 

 richer and purer than, the zinc ores of the most noted localities in Europe ; 

 and there is no reason why they should not be worked with profit to the 

 miner and smelter, as well as with benefit to the State of Arkansas in 

 particular, and to the United States in general. 



The manganese ores have, chiefly, been found in the cavernous sub- 

 carboniferous limestones. These ores appear to be very abundant. A 

 compact variety, allied to psilomelane, is the kind which I found most 

 common on the surface, but there are other softer varieties, which have 

 proved, on analysis, to compare favorably with those of Thuringia, the 

 most celebrated European locality. 



Arkansas promises, also, to aftbrd considerable lead ore, which occurs 

 both in the magnesian limestones of lower silurian date, and in the sub- 

 carboniferous limestones ; also in the slates of the base of the millstone 

 grit, where these border on the confines of the granite region of Pulaski 

 county. 



The lead ore in this latter position is rich in silver, probably more so 

 than the argentiferous galenas of Europe, which have been wrought to 

 any extent. The only ore, which has been cupelled in my laboratory, 

 that surpasses it in the per eentage of contained silver, is some of the 

 steel-grey, finely crystalline argentiferous galena from Villeport, near 

 Lozere, in France. 



Fragments of a porous lead ore, picked up among the rubbish at the 

 mouth of one of the shafts in Pulaski county, yielded by cupellation from 

 the reduced lead, at the rate of 224 ounces from the ton of 2,000 pounds ; 

 and a specimen of a bright, steel-grey ore, finely crystalline in its struc- 

 ture, from the same mines, obtained in Little Rock, gave as much as 339.2 

 ounces to the ton of 2,000 pounds. 



The cherty limestone, which underlies the barrens and prairies of the 

 north-west part of the State, promises to afford rich deposits of lead ore, as 

 the geological formation is a complete counterpart of that around the 

 already famous lead mines of Granby, in -Newton county, Missouri. 



