64 GEOLOGICAL RECONNOISSANCE 
the carbonates, is less valuable as an ore, since it is more expensive and 
difficult to roast, smelt, and reduce to the metallic state. 
The chemical analyses even of the associate dolomitic rocks and red 
clay, filling the interstices between the rock and ore, afford a small per 
centage of zinc, viz: two per cent of carbonate of zinc, in the magnesian 
limestone taken from the Hoppe mine, and about one-thirdfof one per 
cent. in the red clay. 
For the details of analysis, consult the Chemical Report of Dr. Elder- 
horst, where a statement will be found of the value of the Arkansas zine 
ores, compared with those of the most productive zinc districts of Europe. 
Since all the zinc at present consumed in this country is imported from 
Europe, and subject to a duty of 4 per cent. on crude zinc, and 24 per 
cent. on all manufactured articles, the establishment of furnaces for the 
smelting of these very productive ores of zinc of Arkansas, would, indeed, 
be a national benefit, since the quantity of crude and manufactured zinc, 
imported into the United States, according to the last published state- 
ments, amounts very nearly to nine hundred thousand dollars worth of 
this useful metal. 
