TREATMENT OF SULPHUEET OEES AT CHARACTERISTIC MIXES. 119
$1. The engineer, fireman and top-labor "worked in two shifts of twelve hours each, ^"o definite information could be gained regarding the cost of mining; but under the conditions existing, it must have been excessive. The mill is a 20-stamp one, built by the Mecklenburg Iron "Works.1 The mortar (fig. 19) is of a modified California type, and of medium width and depth. A novel feature in this mortar is a large opening above and in back of the screen by which the inside of the screen can be reached to clear it of foreign clogging matter. The inside plates may also be taken out through it without disturbing the screen. The weight of each stamp is 750 pounds, given 5- to 7-inch drop, 90 drops per minute. ISTo inside plates are used at this mill. The height of the discharge is 5 inches, when the dies are new. The screens are 40-mesh, brass wire. The outside plates are similar to those at the Haile mine (see p. 136) The amount of ore milled was about 1 ton per stamp in 12 hours. About ■J of the gold extracted was saved by amalgamation. The tailings from the plates were concentrated on 2 True and 2 Triumph vanners, producing about 1 ton of concentrates in 12 hours, running from $30 to $40 per ton.
The concentrates were roasted in a large reverberatory furnace located in the mill building, the area of the hearth being 9x41^ feet. The capacity of this furnace was stated to be 4 roasted tons in 24 hours at a cost of $1.25 per ton. The furnace was worked in two 12-hour shifts with two men on each shift, head roaster at $1 and helper at 85 cents. Two cords of wood, at $1.25 per cord, were burnt in 24 hours.
The chlorination was carried on in a 1-barrel plant with a capacity of 4 roasted tons of concentrates per 24 hours. The building is arranged for the addition of another barrel which would allow the same work to be done in 12 hours, giving better opportunity for precipitation, and reducing the total cost of chlorination. The charge and the method of working was identical with that pursued at the Haile mine (see p. 140).
1 The Mecklenburg Iron Works of Charlotte, N. C, Captain John Wilkes, Manager, make a specialty of gold-mining and milling machinery. In the summer of 1895 this company erected a 5-stamp test mill at their works, connected with a complete chlorination test plant having a capacity of half a ton of raw concentrates per day. As being of interest and value in a paper of this kind, we have obtained from them the following list of the cost of milling and chlorination plants erected in the South. The figures given are outside ones and apply in each case to a complete automatic plant.
The cost of the machinery for a 10-750-pound stamp mill with grizzly, crusher, self feeders, silvered inside and outside plates, Triumph concentrators (4 to every 10 stamps), engine and boiler, together with all attachments, and plans for erecting and locating machinery, is given at $5700 f. o. b., Charlotte, N. C. The same for a 20-stamp mill is $10,850.
The complete cost of a 10-stamp mill as above, set up (in the vicinity), will be about $8000. Of a 20-stamp mill, about $14,000.
The approximate cost of a 1-barrel chlorination plant with two reverberatory furnaces, erected, is given at $5500. The same for a 2-barrel plant with four furnaces at $9700.
The complete cost of a 10-stamp mill with concentrators, roasting furnaces and a Thies chlorination plant with all necessary power and expenses may be figured at $1200 per stamp. For a 20-stamp mill at $1000 per stamp, and for a 40-stamp mill at $900 per stamp.
The price of shoes and dies of a chilled charcoal iron mixture is 3 cents a pound f. o. b. works.
