52 ECONOMIC GEOLOGY, 



thus both the mining district be benefited and the prices of the phosphates be reduced, 

 and the whole community reap the advantages of lower prices of fertilizers. 



The Hunt and Douglass Process. 



Other localities of copper are numerous, especially in the Connecticut 

 valley, as in Haverhill, Orford, and Lyme. These and others are men- 

 tioned in the catalogue of mineral localities in Part IV. Some of them 

 may prove valuable as mines after exploitation, especially one on the 

 west flank of the hill between Mts. Cuba and Smart. 



Copper is reduced at West Fairlee, Vt.. by smelting. The ores of east- 

 ern Vermont and those in New Hampshire south of Woodsville, belong 

 to a different formation from those mentioned in the Ammonoosuc dis- 

 trict, — the Coos instead of the Huronian. Some authors, especially the 

 managers of mining companies, inform the public of their identity. But 

 an examination of the rocks associated with the two will show that our 

 copper veins belong to at least three distinct periods. Our ores are usu- 

 ally low grade, and hence can be easily reduced by a wet process cheaper 

 than by smelting. Having investigated the merits of the Hunt and Doug- 

 lass process, I think it one well fitted to reduce our ores, and herewith 

 present a brief notice of it, compiled from an authoritative sketch in the 

 Mineral Resources zuest of the Rocky Mountains, for 1876: 



This is what is technically called a wet method, because the copper is removed from 

 its ores in a dissolved state, the solvent employed in the present process being a 

 watery solution of neutral proto-chloride of iron and common salt. Most oxidized 

 compounds of copper, — whether obtained artificially by roasting sulphuretted ores, or 

 found in nature in the form of carbonates and oxides, — when digested with such a 

 solution are converted into a mixture of proto-chloride of copper, which are dissolved, 

 while the iron of the solvent separates in the form of insoluble hydrous peroxide of 

 iron. When the solution of chlorides of copper thus obtained is brought in contact 

 with metallic iron, the copper is separated in a metallic crystalline state, while the 

 iron passes into solution, reproducing the proto-chloride of iron, thus restoring its sol- 

 vent powers to the liquid, which we shall call " the bath," and fitting it for the treat- 

 ment of a fresh portion of copper ore. This process of solution and precipitation can, 

 under proper conditions, be repeated indefinitely with the same bath, the only reagent 

 consumed being the melpllic iron. 



The chief advantages which wet processes possess over smelting lies in the economy 

 of fuel. To extract copper from a low grade ore by smelting, five or six furnace opera- 

 tions are necessary, and about one ton of coal is consumed for each ton of ore treated ; 

 while for the various wet processes, a single calcination, in which not more than 300 



