710 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Discussion. Smelting is conducted so methodically in Leadville that when the 

 writer collected the specimens of slag it was done at random, since he felt convinced 

 that the examination which he was about to make would only furnish additional proof 

 of the admirable method employed; but the preceding table shows that he was greatly 

 mistaken in this anticipation. Laying aside accidental slags, and discussing ouly the 

 normal ones found by thousands of tons on the refuse-slag heap, it is found that at 

 the Grant smelter, for instance, the composition of smelting charges has been altered 

 from the singulo-silicate type to the acid type, and with what results? The old slag- 

 heap and the new slag-heap are several hundred feet apart the first immediately in 

 front of the furnaces and the second outside of the works at the bottom of California 

 gulch so that a mistake on the writer's part in the collection of the specimens was 

 impossible. Now, Table XI shows that the new slag, No. 11, contains 5.1 ounces of 

 silver, while the old slag, No. 15, contains only 3.8 ounces; and at these works it is the 

 poorest slag that is resmelted, while the richest is carried away to an almost inaccessi- 

 ble spot. At Messrs. Billing & Eilers's smelter the same is remarked. It is the poorest 

 slag, No. 29, containing only 0.5 ounce of silver, that is resmelted, while the richest, 

 No. 30, containing more than three times as much silver, or 1.6 ounce, remains on the 

 slag heap. The compact, flue-grained slags, which represent slags of the singulo-silicate 

 type, are conspicuous throughout Table XI for their low contents in silver, and yet 

 we see two of the largest smelters, those of Messrs. Gumming & Finn and Grant, 

 adopting slags of the acid type, containing four and six ounces of silver, like Nos. 7 

 and 6, and four and five ounces, like Nos. 12 and 11. 



The blame for this belongs somewhere, and it is probable that the superintend- 

 ents are constantly misled and misguided by the assayers, chiefly for the reason that 

 the scoriflcation process is not to be depended upon in the assay of slag and that the 

 crucible process ought to be substituted for it. The clearest result of au inspection of 

 Table XI is that there is no relation whatever between either the appearance or even 

 the composition of slag and its contents in silver, and that smelters ought to give spe- 

 cial attention to the assay of these products. 



The process of shelling out the slag, which has been described in smelter C, 

 induced the writer to make a few experiments on the distribution of silver in the cakes 

 of slag, and specimens 16 and 17 were prepared specially for this purpose from the 

 same slag-pot by Dr. M. "W. lies. The shell, No. Iti, contains 2.C ounces of silver, and 

 the poured-out portion 2.5, showing a difference of one-tenth of an ounce in favor of 

 the shell. The difference is much larger between the top shell and the poured-out 

 portion, as is shown by specimens 34 and 35, prepared specially from the same slag- 

 pot by Mr. A. Eilers. The top shell contains 0.15 ounce silver and the poured out 

 portion 0.36 of au ounce. These two experiments seem to indicate that during the 

 process of cooling the chloride of silver, which is only mechanically mixed in the slag, 

 settles, in virtue of its higher specific gravity, by means of a sort of liquation. 

 Specimens 32 and 33 point out the same results. The outer portion of the cakes of 

 slag, in indefinite crystals, assays 1.47 ounces, and the distinct crystals, forming the 

 inner portion or core of the cakes, 0.6. There can be no doubt about these results, 

 since the crystals were detached from the outer portions immediately before assaying; 

 nor can the differences be attributed to the presence of traces of bullion, for in no 

 case did the slag contain even a trace of metallic grains. These results were not sus- 



