GOLD lONIKG IN COLOEADO. 579 



fluid, it will carry particles of the matt suspended in it, involving a loss of 

 metal and the necessity of repeated fusion. 



The principal operations at the works consist in the preliminary prepara- 

 tion of the ores, such as the breaking, weighing, sampling, and assaying of 

 the various lots or parcels as they are delivered for treatment; roasting, 

 which, in the case of hand-broken ores, is done in heaps in the open air, while 

 tailings, the product of crushing in stamps, are roasted in furnaces ; crushing, 

 in rollers, of the roasted ore; smelting, for the production of matt, and the 

 final crushing, packing, and shipment of the latter. 



The ore, when first received at the yard, is deposited on a breaking-floor, 

 where it is broken by hand to the size of a man's fist, or something less. 

 Being thus prepared for the roasting heap, it is very carefully sampled for 

 assay. The method of obtaining a sample, which shall fairly represent the 

 whole mass, is as follows: The ore, in order to be removed to the roasting 

 heap, is shoveled into barrows, each of which is capable of containing 200 

 pounds, and standing balanced on a scale. From each barrow, or, in some 

 cases, from each alternate barrow, a shovelful is taken out and laid aside for 

 sampling. When any given parcel of ore has thus been broken and weighed, 

 the accumulated samples are taken together and reduced in size sufficiently 

 to pass through a No. 4 screen — that isj a screen having four meshes to the 

 lineal inch. The pile, having passed through this screen, is arranged in a 

 conical form, divided into four quarters, of which two diagonally opposite 

 quarters are taken, reduced still further in size so as to pass through a No. 8 

 screen. The operation of quartering and further reducing is repeated so that 

 the material will pass through a No. 20, and subsequently, in similar manner, 

 through a No. 40 screen, from which a final sample is taken, reduced so as to 

 pass through a No. 80 sieve, and then assayed. By the assay of this sam- 

 ple, the value of the gold, silver, and copper contained in the ore is deter- 

 mined, and, in accordance therewith, the amount to be paid for the parcel is 

 fixed by the established scale of prices, given on a following page. 



In shoveling the ore into barrows, for the purpose of wheeling it to the 

 roasting yard, it is thrown on a screen, by means of which the finer por- 

 tion is separated from the coarse pieces, the former being reserved for cover- 

 ing the latter when laid up in heaps for roasting. 



