Year: 1878

ted the concentration works of the Silver King Company, this being the nearest point to their mine at which water in sufi- cient quantities for the use of the works could be obtained. Owing to the success that has attended the working of the ores of the Silver King mine by the Frue con- centration process, after failure to treat them by amalgamation, concentration has come to be looked upon as the only method by which the ores of this district gen. erally can be successfully worked This method of handling ores has the merit of being cheap, simple and expeditions, the objections to its employment being that it | is incomplete and applicable only to cer- tain varieties of ore. It is used with great advantage to separate, by means of spe- 1 cific gravity, all ores having a crystalline structure, from their gangue being espec- ially we'll adapted to the concentration of | sulphurets. The Silver King ores contain large quantities of sulphurets of silver, lead, antimonF and copper, with asprink- | ling of carbonate of the latter, about twenty per cent. Of the silver existing as chloride or "dry chloride" as distinguish ed from horn silver. These sulphurets are crystalline and readily break from the gangue under the stamps. Thus they are practically all saved, but the dry chloride being light and exceedingly frlable is, at the same ti1ne, carried over with the tail l ings and lost unless rescued by another process. Were the metal all contained Tn four per cent would be lost, With mines occurring in the limestone formation, however, entirely different conditions are presented. There is a large group of this class of lodes bordering Queen Creek on the north, the ores of which are character ized by the presence of gray carbonate of lead III considerable quantities. This mineral carries the silver which blackens it, but does not otherwise alter its appear ance or fracture It is amorphous or en- tirely homogeneous in structure, and therefore cannot be concentrated, because no matter how fine it be pulverized, each grain still possesses the same specific gravity, and the only result of concentra- Don will he a separation of the coarse from the fine particles It is proposed, by parties interested in these mines, to employ this process in the treatment Of this ore, but experience will, ] fear, dem onstrate to them. as it has to the writer, the folly of the undertaking. How this ore really should be handled remains to be determined. It is not to be presumed that it will amalgamate, and, though it carries fair proportion of lead it is not rich enough in silver to pay for smelling where wood and iron Gts requisite fluX) are so far distant. Still there it may be

 

 lead will run into galena as soon as con- siderable depth is reached in these mines, when concentration can be practiced with advantage.

 ANOTHER FORMATION AND A DIFFERENT Further south, across Queen Creek, which cuts through the silver bearing belt, the proportion of lead contained in the ore is so small that this metal no long CT interferes with amalgamation. Here the prevailing ore is horn silver, in itself not well adapted to concentration, while the admixture of the dry chloride is too great to admit of a profitable application of this process. Continuing south we find 1 the carbonate of lead decreases, while 1 that of copper increases, until this latter ! becomes the predominant metal. A cer- tain percentage of copper has always been considered advantageous in amalgamation, and even when present in such abundance as to depreciate the quality of the bullion this is not a serious trouble. These argen- tiferous copper ores will, in fact, very likely be found useful to mix with other ores in preparing them for amalgamation, which will surely be the process employed for their reduction until the mines reach considerable depths, when the ores may change and other means for treating them will come into use. The opponents of this process point to several unsuccessful attempts which have been made at en- ploying it, but to this it may be replied that the ores experimented on were, with one exception, taken from mines lying in the eastern or gneiss formation, all highly sulphurated and carrying lead, antimony and arsenic in such quantities that no skillful metallurgist would undertake their treatment without roasting. The re- suit of the other trials have never been

 made public, though it was hinted by one who ought to know, that very high per