GOLD MINING IN COLOEADO. 547 



SECTION II. 



TEEATMENT OF THE OEES. 



It has already been said that the ore produced by the gold-bearing veins 

 of Colorado is generally divided into two classes that are treated by diiFerent 

 methods for the extraction of their valuable contents. The first-class, which 

 is but a small proportion of the whole, consists of a selected portion of rich 

 mineral that occurs in the vein in a somewhat concentrated form, or mixed 

 with comparatively little gangue. The chemical nature of the minerals with 

 which the gold and silver are combined, or intimately associated, is such that 

 nicely-adapted and somewhat costly methods of metallurgical treatment are 

 required in order to extract a reasonably high percentage of the value con- 

 tained, and the ore selected for such treatment must consequently be rich 

 enough to leave a profit after paying the costs of the operation. The second- 

 class, comprising the bulk of the ore produced, is vein-rock or quartz, through- 

 out the mass of which the gold-bearing mineral is sparsely distributed, and of 

 which the low average value demands a cheaper method of extraction. The 

 valuable mineral of the second-class ore does not appear to differ essentially 

 in chemical composition from that of the first-class, and when treated in the 

 simple manner now in general use, yields a very much lower percentage of its 

 value than does the first-class under more exact methods, but, owing to its 

 meager distribution through the gangue, the value of the whole is so low that 

 the greater percentage that might be extracted by any better methods yet 

 available would not be sufficient to pay the increased costs of working, so 

 that for the present, at least, or until new improvements are made practicable, 

 the miner must needs be content with the cheaper, though less efficient, 

 methods. 



The two principal methods now in use in the gold district of Colorado 

 are, for the high-grade or first-class ore, smelting, by which the gold, silver, 

 and copper is obtained in the form of regulus, or crude metal, which is at 

 present sent to Swansea in that form for separation and refining ; and, for the 

 second-class ore, crushing by stamps and amalgamating the gold by means of 

 quicksilver. Besides these two methods, some other processes are in use to 



