GOLD DEPOSITS. 67 
At the Haile mine the ore values are distributed as follows: The uppermost portion of 1 he 
deposits, which was worked as placer ground, was rich. Below this surface mantle the 
values have decreased, so Car as known, rather steadily, although pockets of sulphide ore of 
better than average grade have been encountered, probably most commonly near the 
boundary of general decomposition. The limit to which economic mining can be carried 
appears to bear a pretty definite relation to distance from the surface, and that distance is 
not great and reaches not very far — usually less than 200 feet — below the limit of complete 
oxidation. Moreover, thin films and scales of pyrite and of free gold have been found in 
joint cracks which give every appearance of having been formed since the silicification of 
the rock and the attendant ore deposition. Thin films of free gold are commonly found on 
molybdenite associated with heavy pyrite bands. Finally, it is certain that the compara- 
tively plentiful gold which was found at the surface of these deposits and which was derived 
from higher portions of the deposits now eroded away has remained in that place undis- 
turbed for a long period — in fact, ever since the peneplanation of the region, which probably 
took place as early as Tertiary time. Erosion at these places has been almost at a stand- 
still and the process of secondary enrichment of the deposits, slow as it is, has had time to 
be effective. The writer does not undertake to say that secondary enrichment has had 
much to do with the vertical distribution of the gold, but it certainly seems possible that 
it has. If such a process has gone on, the action has differed from that common in copper 
deposits, inasmuch as the copper is derived largely from the upper portion of the deposit in 
situ, while the gold is supposed to have been dissolved mainly from gold which rested upon 
what was then the surface of the deposits and which had been previously concentrated by 
mechanical means virtually as placers. (See pp. 74-75.) 
Whether or not secondary enrichment has taken place, the present ore bodies of the 
Haile mine certainly represent original loci of more than usual concentration of the gold 
in the deposits. 
VALUE OF THE ORES. 
The value of the ores is of course dependent on the distribution of the gold. Gold is 
present in much greater quantity than the amount of workable ore would indicate. In 
the walls of the veins and as horses and outer zones of the large replacement bodies, as 
well as within many veins, there is much material carrying gold from a trace up to the 
minimum amount for which mining can be profitably conducted. Of the pay ores the 
values vary greatly', depending as much on the cost of winning the gold as on the absolute 
richness of the ore. Some shoots or parts of shoots have been found which carry ore valued 
at several hundred dollars per ton. The Kings Mountain mine had some very rich ore and 
ore of high grade has been taken from the Thompson mine. Small, very rich pockets 
have been found in numerous places. The ore mined from the fissure veins has on the 
whole been of considerably higher grade than that from the replacement deposits. This 
is probably due both to the concentration along narrow zones of the gold which the solu- 
tions held, rather than dissemination through larger masses, and to the fact that owing 
to their small size and irregularity in form and richness veins can not be profitably worked 
when below a certain value; while the large replacement deposits, of more regular outline 
and certain value, can be made to yield a profit when far below that value per ton. 
The ores of this region must on the whole be classed as of rather low grade. While 
some few mines may always have raised ores of good value, the vein mines have probably 
produced ore running on the average not better than $8 to $12 and the replacement bodies 
have averaged from $2 to $12 or $15, the value of the ore in the second case depending 
rather on the extent to which mining was carried into the outlying leaner portions of the 
deposits than on the actual amount of gold present. 
The values occur both as free gold and in pyrite. It is certain that original, native 
gold has been deposited from the vein solutions to some extent. At the Blackmon mine, 
for instance, below the general depth to which surficial alteration has reached, the greater 
portion of the gold occurs free. At the Haile mine also some of the free gold associated 
with pyrite and molybdenite was perhaps originally deposited as such. In most cases, 
