GOLD DEPOSITS. 69 
the commoner sulphides of iron and copper, small amounts of arsenic, antimony, bismuth, 
and molybdenum sulphides and one or more tellurides were present in some cases. Fluor- 
ine and probably boron were contained in some of the solutions. A little phosphoric 
acid was present and allowed the formation of apatite. There is little or no evidence that 
carbon dioxide was present. 
The nature of these materials deposited from solution, as well as the general effect on the 
wall rocks, an effect resembling that produced by contact metamorphism, points to the con- 
clusion that the ore-bearing solutions were concentrated and at high temperature. The 
almost entire absence of banding in me veins and the widespread effect of the solutions in 
the replacement deposits, as shown by the large size of these deposits, may be taken as addi- 
tional evidences of concentration of the solutions. 
SOURCE OF THE MATERIALS. 
The character of the minerals deposited, the metasomatic action on the surrounding 
rocks, the structure of the veins, and the amount of erosion which the region has undoubt- 
edly suffered since the deposits were formed are grounds for the belief that the ore bodies 
now exposed were formed far below the surface of that time. The character of the solu- 
tions, moreover, points not only to deposition at high temperatures but to their derivation 
far below. The source of these materials was therefore at greater depth than their place 
of deposition, and the solutions were at even higher temperature at the beginning of their 
upward journey than when the dissolved materials were precipitated. 
Such extremes of depth and temperature suggest at once a magmatic origin of the solu- 
tions. Such an origin can not be established with absolute certainty, but a number of facts 
appear to favor it. Granite is known in the vicinity of many of the mines. How large a 
body of granite exists below the present surface it is of course impossible to say, but it is 
probable that the areas exposed are small parts of a much larger mass. The absence of 
granite outcrops immediately around the mines does not, therefore, preclude the possibility 
that the veins or solution channels reach granite somewhere below. 
The intimate association of granitic or aplitic dikes with the quartz-tourmaline veins of 
the tin belt and the close resemblance in many respects of these veins to the gold-quartz 
veins make the relation of the gold deposits to the granite rather probable. This prob- 
ability was so apparent and the resemblance of some of these tourmaline veins to the 
auriferous veins of the Lockhart mine in Dahlonega was so marked that it was decided to 
have specimens of some of the tourmaline veins assayed for gold. Two samples were 
selected — one from the quartz vein, which occurs close to the aplitic dike at the Jones mine, 
the other from a quartz-tourmaline vein, reported to be auriferous, near the pegmatite dikes 
at the Faires mine. It should be stated here that the specimens tested were not collected 
in the field with the assay in view; otherwise more conclusive results might have been 
obtained. Very careful assays were made by Messrs. Ledoux & Co., of New York.a The 
results were as follows: 
No. 1. Quartz vein, with tourmaline, Faires mine, 0.0003 ounce per ton. 
No. 2. Quartz vein, with pyrite, Jones mine, 0.0111 ounce per ton. 
No. 1, from the Faires mine, is of course valueless, and the assay doubtless means that 
no gold was present in the sample submitted. The writer is inclined to believe, however, 
a The method used in these determinations is here quoted from a letter from Ledoux & Co. to the 
Director of the Survey: 
"To avoid possible contamination or salting the samples were ground to flour fineness in porcelain 
pebble miils, which had been cleaned by grinding clean quartz in them for several hours, followed by a 
charge of common salt. 
" The pulp from the pebble mills was divided into lots of 2 assay tons, each of which were run sepa- 
rately by crucible assay. In the case of ' S. C. No. 7 ' [No. 1] eight charges, making 16 assay tons, were 
made, and in the case of ' S. C. No. 42 ' [No. 2] nine charges, making 18 assay tons, were made. In each 
case all of the sample was used. 
" The buttons from the crucible assays were united and scorified to a size suitable for cupellation. 
An excess of silver (20 mg.) was added to the scorifiers for the purpose of preventing cupel losses of the 
gold. . . . The silver beads obtained were parted and washed in the usual way, and the gold weighed 
on a balance sensitive to one four-hundredth mg. 
"Charges of flux equal in weight to those used on the ores were run through contemporaneously with 
them and treated in exactly the same way, but no visible amount of gold was obtained in the blanks. '■" 
