COLLECTIONS IN ECONOMIC GKOLOGY AND METALLURGY. 13 



a cam motion, and allowed to fall by its own weight by suitable me- 

 chanical arrangements. The stamp weighs 500 pounds, and falls IG 

 inches, thirty times per minute. As the stamp falls u])on the ore, it is 

 crushed, and as soon as it is fine enough, it passes out of the mortar, 

 through the screen, by the water flowing through the mortar. After 

 passing the screen it is carried along over amalgamated silver-plated 

 copper plates, which catch a still further portion of the gold. Below 

 the plates there are arrangements for catching the amalgam that is 

 carried along mechanically from the plates, and also to collect some of 

 the richer portions of the material that will not amalgam'ate. After 

 passing over these appliances the material passes through a concentrat- 

 ing process, whereby the waste material is separated and thrown 

 away, while the sulphurets are separated, and further treated at other 

 works. 



These sulphurets as a general thing stdl retain about 10 per cent, of 

 the gaugue material, and from 0.5 to 1 ounce of gold per ton ; they some- 

 times contain a valuable amount of copper, and when roasted form a 

 useful flux for smelting operations on account of the iron they contain ; 

 they are in considerable demand lor this purpose. Occasionally rich 

 sulphurets are picked by hand from the ore and sold to the smelters. 



To illustrate this process seven specimens collected by Mr. E. N. 

 Eodgers, in November, 1884, are shown. 



(1) Ore, consisting of various sulphurets, xiriucipally pyrite and clialcopyrite in 

 quartz and feldspatliic material; aii averairefair sample of the material treated at the 

 mill. Bobtail Mine, Blackhawk, Gilpin County, Colorado. (5.58ri7.) 



(2) Battery Pulp, showiuo- the condition of the ore after it has been subjected to the 

 pounding of the stamxi in tlie battery and to the action of mercury, whereby a large 

 portion of the gold is extracted. (.^15838.) 



(3) Stock, or the ore after crushing, a-< it passes through the sieves and over amal- 

 gamated copper plates where the rest of the gold that will amalgamate is extracted. 

 (55839.) 



(4) Gold amalgam, as scraped from the copper plates, weighs 6 ounces and contains 

 $40 worth of gold. (55842.) 



(5) Retorted amalgam, or gold sponge, weighs 2 ounces, 15 pennyweight, worth 

 $46. (55843.) 



(6) Concentrates, consisting of the sulphurets that have been separated from the 

 ore after the extraction of the gold, they yet contain about one ounce of gokl per ton 

 that can not be recovered by amalgamation; thev are, therefore, sold to the smelling 

 works where, after roasting, they serve as a valuable flux, as well as a source of gold, 

 in the fusion process. (55840.) 



(7) Sand or tailings, consisting of quartz and other waste material in the ore, 

 thrown away as valueless. (55841.) 



THE EXTRACTION OF SEVERAL METALS BY SMELTING. 



To illustrate the extraction of gold by smelting, a series of fourteen 

 specimens from the Newark Smelting and Refining Works of E. Bal- 

 bach *& Son are shown. The process followed at these works is a 

 double one, embracing the separation of gold and silver from ('op])er, 

 and also combining the smelting; operation with an ekMUioIytic process. 



