136 GEOLOGICAL RECONNOISSANCE 
geological corps, north of the Arkansas river: i. e., in the part of the State 
on which I am now 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 zine 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 afford 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 centage 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 strue- 
ture, from the same mines, obtained in Little Rock, gave as much as 839.2 
ounces to the ton of 2,000 pounds. 
The cherty limestone, which underlies the barrens ei 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. 
