68 GOLD AND TIN DEPOSITS OF SOUTHERN APPALACHIANS. 
however, it is likely that the gold which has been found in the metallic state, both in the 
deposits in situ and in the placers, has been liberated from pyrite by oxidation. What- 
ever the original condition of the gold may have been it is certain that nearly all the 
gold occurring in the oxidized portion of the deposits has been found in the metallic 
state, and that as the proportion of sulphides increased the amount of free gold has 
steadily lessened. To judge from statements of the value of these decomposed out- 
crops or gossans it appears that they were decidedly richer — in some cases several times 
richer — than the average grade of sulphide ore below. The solution and carrying away 
of portions of the vein material, leaving the gold behind in consequently increased 
proportions by weight, have been responsible for much of this added value which the 
gossans show. It is probable, also, that gold from overlying portions of the vein has 
gradually been left behind as the other lighter constituents were eroded away, and has 
settled down with the degradation of the country. This last kind of concentration is con- 
sidered more explicitly in connection with the placer deposits (pp. 74-75). In spite of these 
two explanations of the greater richness of the upper portions than those found below, 
it is difficult to rid one's mind of the feeling that the upper portions were always richer. 
For this belief, however, there is little ground. Probably the greater proportion of the 
output of this area, exclusive of that from placers, has been from sulphides. 
The fineness of the gold averages about 0.900, but ranges from 0.700 to nearly 1.000. 
Silver is the chief ingredient to lower the fineness. 
Complaint has often been made that returns from shipments to southern smelters have 
not agreed with the actual value of the ore. The writer comments on this topic only to 
say that he heard of no case where careful, systematic sampling was done by the shipper 
and to point out how necessary it is that such sampling of the ore be done in order to 
determine its average worth and how nearly impossible it is even with absolute imparti- 
ality to choose from a lot of ore one or a few specimens' which really represent the whole. 
GENESIS OK THE DEPOSITS. 
In the preceding sections it has been assumed that these gold ores have resulted from 
deposition by aqueous solutions. This assumption is so completely sustained by the vast 
array of facts available both here and in other gold regions that further consideration 
need not be given to this subject. Granted, then, that the ores have been deposited by 
solutions, the factors which enter into the consideration of the origin of the ores are the 
nature of the solutions, their source, and the manner of deposition of their dissolved mate- 
rials. 
It is regretted that a thorough investigation of these deposits could not be made. The 
reconnaissance character of the examination on which this report is based has not justi- 
fied the devotion of such detailed and thorough study in the office and laboratory as a com- 
plete survey would demand. Moreover, while the deposits deserve careful and complete 
investigation because of their complexity, for that very reason it is difficult to obtain a 
fundamental comprehension of their character. 
CHARACTEB OF THE SOLUTIONS. 
Without numerous analyses showing the changes effected by the solutions in wall rocks, 
much concerning the nature of these solutions is left to assumption. From the materials 
which constitute the fissure fillings, however, it is certain that silica was the most abun- 
dant of the dissolved substances. Metallic sulphides, chiefly pyrite, have also been impor- 
tant. The conversion of feldspar into sericite and of amphibole into biotite indicate that 
potassium has been taken from the vein solutions by the surrounding rocks and that sodium 
has been added to the solutions. The production of the micas and of chlorite may mean 
that the solutions carried aluminum. A small amount of calcium may have been carried by 
the solutions to form the apatite, or the calcium may have been derived from the replaced 
rocks. The presence of such oxides as ilmenite and possibly hematite, magnetite, and 
cassiterite point to conditions rather unusual in the formation of gold deposits. Besides 
