70 GOLD AND TIN DEPOSITS OF SOUTHERN APPALACHIANS. 
support of workmen and drills. It was found that in a raise driven at an angle of about 45° 
the broken rock would just servo as a foundation from which to work. The raises were 
therefore started from the levels at the hanging-wall side of the ore body and driven upward 
at 45° diagonally across the deposit. When the foot wall was reached the raise was turned 
to the right or left, first along the foot wall, then toward the hanging wall, and finally back 
again toward the foot wall, always being pointed upward at 45°. A spiral raise was thus 
driven, all in ore and without the use of timber. The cost of increased length of the raise 
was more than balanced by the saving in timber. 
As the better grades of ore in these deposits were exhausted it became apparent that the 
shaft-level method of working when applied to the larger surrounding bodies of lower- 
grade ore would necessitate timbering and become too expensive. Since the workings 
were not very deep, it was found possible to extract the low-grade ore and take out the 
higher-grade pillars by means of open cuts. This method is now being used at the Haile 
and Brewer mines, has been used at the Blackmon mine, and it was announced as the inten- 
tion of the management to put it in operation at the Colossus mine. No timber is 
required and the rock can be broken by quarrying methods. The result is that although 
in some cases considerable barren ground has to be broken, especially from the hanging 
wall, the cost of mining is greatly reduced. At the Haile the ore is hoisted in skips 
running on inclined tracks laid on the foot wall. At the Brewer a tunnel connects with 
the bottom of the pit or open cut and the ore is trammed out through it. 
The depth to which open-cut mining can be carried with profit will of course depend on 
the strength and firmness of the walls, the size of the deposit, and whether it stands ver- 
tically or dips beneath the surrounding rock. 
METHODS OF EXTRACTION. 
The methods of extraction of placer gold have already been mentioned under the 
head "Methods of Mining." The same applies to the gossans of many veins. Hard rock 
containing free gold, either original or derived from oxidation of sulphides, is generally 
stamped and amalgamated. Sulphide ores containing also native gold are in most 
cases stamped, amalgamated, and concentrated, the concentrates being either shipped 
for smelting or else chlorinated or cyanided on the spot. At the Ferguson mine amalga- 
mation has been discarded and the stamp-mill pulp is concentrated, the headings saved for 
roasting, and'the tailings cyanided. At the Colossus mine a . r )00-ton mill nearlv completed 
will crush the ore in rolls to 30 mesh and then cyanide direct. Both weak and strong 
solutions will probably be used. At the Haile mine stamping of the ores is followed by 
amalgamation of the free gold, while the concentrates are treated by the barrel-chlorination * 
process, which was invented by Captain Thies, the former manager of the mine, and which 
now in successful operation in the ^Vest, particularly on the ores of Cripple Creek, and also 
in Australia. The same methods have been employed at the Brewer mine. 
Throughout the area much difficulty has been experienced in extracting the gold froi 
sulphide ores by amalgamation, even when a considerable proportion of the values is free 
gold. From what can be learned of these operations, it seems probable that much of thi 
lack of success may be attributed to lack of experience in the stamp milling of ores. Just 
the right combination of weight and drop of stamp, height of discharge, size of screen, anc 
amount of water seems in many cases to have been missed, and in consequence the tailings 
were rich. 
It is doubtful if the ores of this area can be successfully treated without concentration, 
roasting, and subsequent lixiviation of the sulphides. 
COSTS OF PRODUCTION. 
Little satisfactory information could be obtained on the subject of costs, as the mining 
<• »i i ipanies are rather reticent about it. Labor and fuel are low in price and all kinds of 
operations can be carried on during almost the whole year. Pumping has to be done in 
nearly all the mines, but the quantity of water is not excessive. 
