Labor: 26 days per ton of ore,* days.. Table of cost per ton of ore in units of labor and material. First and second fusions Third fusion Cupellation Total 0. 1476 0.0180 0.24 0.69 0.37 To this must be added a small quantity of wood, or refuse charcoal, and labor used in roasting the matte. The above is the cost for ores of the richness above given. With richer ores there is more matte to treat, and the expense of fuel, labor, and lead is therefore greater, and the cost per ton is more; but proportionately richer ores are cheaper to treat than poor. The following table gives the relative cost for various ores, the poorest being taken as unity: The Lend ore falls under the first class. The milling ore of Colorado is worth from $15 to $30 a ton, and comes under the same category. The Colorado "smelting ore" so called is probably mostly in the second and third ranks. Losses. By reference to the above tables it will be found that the following is the loss and gain of the year: * In calculating this it is to be remembered that 28 tons of matte from the previous year were smelted, which must be counted as ore in calculating the expense of charcoal and labor. These amounts are, however, so small that it is impossible to say whether the assayers' errors do not amount to more than the reported loss and gain. Dr. Turner's opinion, founded upon years of experience, and comparing the analyses of the ore with the yield by amalgamation and fusion through several years, was, as I have said, that he could count upon extracting more than ninety per cent. of the silver and ninety-six per cent. of the gold by the two processes of amalgamation and fusion. The loss of lead was nine per cent. of the amount charged. The cost of all the operations at Lend, in 1866, was $883.88, and the balance-sheet shows a profit of $1,355. The expense was proportioned as follows: Labor, 17, materials, 43, direction, 40; total, 100. I have dwelt thus particularly upon the minutiae of each operation in order to indicate the means by which such excellent results are obtained. In our own country the losses in working silver-ores by fusion are so great (frequently from twenty to thirty per cent. in the West) that we can ascribe them only to very rude working. But even in works more pretentious in expense than the somewhat incomplete establishments to be found in the Territories, and which base upon long experience a claim to skillful treatment, we find such reckless application of heat and careless handling of valuable ore as must and does cause great loss. We see ore, worth one or more hundred dollars a ton, thrown in the state almost of powder into furnaces through which flames are roaring almost as violently as in a puddling-furnace. We see alloys of silver, lead, and zinc subjected to distillation in anthracite-fires at a heat far greater than that which has caused the rejection in Europe of all furnace methods of treating these alloys. At the works which I present for consideration all avoidable causes of loss have been eliminated, or their operation reduced, with the greatest care. Two analyses a year determine the proportions of the charges and the composition of the scoria. Larger establishments would require more analytical work, but there is no reason why the largest works should not be conducted with equal care. The cost of the laboratory would not be more than $250, and the work would consume only a few days in each month. Great care is necessary at Lend, because, with so small a quantity of ore, any disregard of proper precautions would hazard the profits of the works. In 1866 only 83 tons of ore, worth less than $6,400 in gold and silver, and containing a ton and a half of copper, were treated. And \yet this small quantity, together with the ore which is treated by amalgamation in the mills, keeps alive two mining districts and a smeltingworks. Beside the miners, an engineer, two smelters, and four assistants have to be supported for the whole year, though the work of smelting occupies only twenty-seven days of twenty-four hours. Of course, such a state of things can be maintained only by low prices, and we find the Austrian workmen paid at rates varying from 27 to 22 cents (coin) a day. Charcoal is 3 cents a bushel, and wood $1.17 a cord. In this country we have larger supplies of ore, sufficient to carry on the largest works on a correspondingly economical scale. The nature and higher value of our ores would enable us to work with less expenditure of labor and material to the Troy pound of silver and gold than at Lend. In considering the results given in this paper for guidance in using a similar process at the West, it is evident that the American ores contain nothing to prevent the application of this method. Antimony, arsenic, and zinc, the bug-bears of the smelter, are, with the exception, perhaps, of zinc, quite as prevalent at Lend as in Colorado. Our ores contain more pyrites than those we have been considering, and there would be H. Ex. 211-27 no necessity of a fusion for raw matte-an operation which has no object but to remove the gangue. Whether there ought to be a fusion for concentration depends upon the richness of the ore and its adaptability to concentration by machinery. A mixture of rich "smelting ore " and concentrated tailings, such as is now worked up by the smelters, could be roasted and immediately fused with lead. One more fusion with a fresh quantity of lead, if there were silver enough left in the matte to pay for the work, and cupellation, would complete the process. We should then have a process divided as follows: 1. Concentration of poor ore. 2. Roasting of concentrated and rich ore. 3. Fusion of roasted ore with lead. 4. Roasting of matte. 5. Fusion of matte with lead. 6. Cupellation. The present imperfect concentration of tailings in Colorado is said to cost $6 a ton. A perfect concentration would cost no more. The other expenses would be Mr. Hague says the millers expect to get 1 ton of concentrated pyrites from 6 tons of tailings, which seems to indicate a pretty heavy loss. At that basis, however, the theoretical expense would be Concentrating 6 tons to 1... Smelting 1 ton, 3.10 days' labor, at $3. Smelting 1 ton, 82.17 bushels charcoal, at 25 cents. Smelting 1 ton, 0.72 cords wood, at $8. Total... Mining at $10.. Total cost of treatment, 6 tons... Cost of one ton... $6.00 9 30 20 54 6 00 41 84 60 00 101 84 16 94 The expense of charcoal ought to be somewhat less than this, for in consequence of the small quantity of material treated at Lend, no less than 2.5 bushels per ton of ore are expended in heating the furnace. If we add one-half more for loss in blowing out, we have the very large proportion of 3.7 bushels-a quantity which would be lessened to 1 bushel if 500 tons of ore were smelted in one campaign. With proper management this could be very much exceeded, so that the expense of charcoal for blowing in and blowing out would be too little per ton to be worth reckoning. It now remains to consider the adaptability of this process to western ores, and I will take those of Colorado as an example, for the reason that Mr. Hague's report on the mines of that Territory offers the best data for the calculation. He gives commercial assays of ores from various lodes, which prove their value to be as follows: The coin value of the first-class ore is therefore $91.36 for the gold and $21.03 for the silver; total, $112.13. By roasting the ore so as to leave one-third raw matte, and smelting with 180 to 195 pounds of lead to the ton, we ought to extract 90 per cent. of the gold,* or 4.05 ounces, worth $83.71; and 73 per cent. of the silver, or 11.90 ounces, wortli $15.35, or $99.06 in all. The cost of this would be about as follows: Mining one ton of ore Roasting: 0.04 day's labor, at $3. 0.029 cord wood, at $8.. 8 months' interest on $10, at 12 per $10 00 $1 20 23 18 63 28 63 Total for roasting and smelting.. Total for mining, roasting, and smelting... If our ore contains no copper, and the matte will not pay for further treatment, and we proceed at once to cupellation, we have in addition : Cupellation: 0.24 day's labor, at $3. 0.37 bushels coal, at 25 cents. 9 pounds lead, say at 5 cents. $0.75 09 5 52 45 6 81 Total for mining, roasting, smelting, and cupellation,.... 35 44 Profit, $99.06-$35.44-$63.62. We have remaining a matte containing $13.07, and probably a certain amount of copper. Let us see whether this will pay to work by itself. The cost will be: *It will be observed by reference to the table of the third fusion that all the gold was extracted by one operation at Lend in 1866. I have, however, adhered to Dr. Turner's general estimate in making the above calculations. This would cause a loss; for calculating 4 per cent. loss on gold and 10 per cent. on silver in the original ore, we have only $7.50 which can be extracted from the matte. The loss would therefore be $3.38, and unless the matte were worked for other products, as for copper, it probably could not be utilized at present, though in many cases it would be required as a basic flux in the first fusion. Considering the present state of the West and proportion of copper in the ore, the process would probably consist of three operations-first, roasting the ore; second, fusion; and third, cupellation, the copper matte being sold. Accepting the Burroughs milling ore as an average of the secondclass ore, we have for this, one ounce gold, worth $20.67, and 4.5 ounces silver, worth $5.81; total, $25.48. The cost of treating it would be: This would leave a matte containing $1.86 in gold and silver, and perhaps some copper. The above calculations are of course theoretical, so far as they relate to works which have never yet been established in the Territory. There may be errors in the prices assumed for labor and materials; but there is no reason why the amount of labor and material expended per ton should be more than at Lend; that part of the calculations is not theoretical. Undoubtedly in establishing such works some difficulties would be experienced, but with a railroad to the foot of the mountains, and the improved facilities for communication, the difficulties in the way * A certain correction has to be applied, because the amount of matte is taken as larger than at Lend. I have assumed it to be 50 per cent. more. Fine ore requires a more expensive roasting than coarse, for which reason I have added 50 per cent. to the cost. Roasting in furnaces, Mr. Hague says, costs $5 in Colorado. |