|
THE JIIXIXG ASD M1LLIXG PKACTICE.
|
113
|
||
|
|
|||
|
The average drop of stamp is U inches; number of drops per minute, 90. The whole machine is well constructed, and admirably fulfills its purpose of handling large quantities of the Dahlonega mill-stuff. The mill is also built with heavier stamps, and some slight changes are made in the frames of these. Xone of these heavier mills were seen in operation; but the setting employed is said to give as great satisfaction as in the lighter ones. Whether the application of this mill would be extensive for harder ores we are unable to judge. It certainly gives the extreme of rapid, crushing, and might be adopted where such an object is in view.
The cost of these mills is light and that of installation small as compared with those of Western type.1
Almost all the mills in Dahlonega are operated by water-power, using turbines of the Leffel type for large quantities and low heads, and wheels of the Pclton type when the water is small in quantity under a high head. The crushing capacity of these mills varies from 2 to 5 tons per stamp of 150 pounds in 21 hours, depending greatly on the nature of the material run through.
In hydraulicking, and subsequent transportation by water, a partial concentration takes place, resulting in the eventual deposition of a largely enriched product in the mill. The light stuff and most of the slimes pass through the mill, in almost all cases without subsequent treatment, and the heavy product remains, the enriching being all the way from 2 to ~> times the original value of the ore in place. Besides this, free gold (generally about one-third of the total amount saved) is caught in the sluices before reaching the mill. Some of the losses in this process are evident from the above. Another serious loss, which is rapidly making itself felt as the mines grow deeper and less decomposed ores occur, is that of gold in the sulphurets. In such ores that carry sulphurets at all it is stated that they will run from 2 to 10 per cent., the concentrates from which are reported to assay as high as $10 and higher. Thus far, concentration has not been carried out on a working
1 The following figures were obtained in the camp as representing- the average cost of a 450pound 10-starap mill of the Hall type, as erected and used in the Dahlonega district: All iron-work for batteries and setting, including copper-plates ff. o. b.
works, Cincinnati)...................................................... $700 00
Freight on same, and cost of erection, about.............................. 500 GO
Buildings, floors and sluices.............................................. 400 00
Engine and boiler, with connections ................. ................. 600 00
Freight on same, about......... ........................................ 150 00
Total cost of complete mill.........................................$2350 00
Water-wheel and installation of same would cost about the same as engine and boiler. Chrome steel (made in Brooklyn, N. Y.) and Wilson pressed steel (made in St. Louis, Mo.) shoes and dies find about equal favor in the district, costing respectively 6 and 7 cents, f. o. b. works. Cast-chilled iron shoes are also used to some extent, at a cost of about 3 cents per pound. Mills similar to the Hall type are also made in Gainesville and Atlanta, Ga. 8
|
|||
|
|
|||