GOLD DEPOSITS. 65 
Sehlegelmilch mines may in part be due to introduction by the vein solutions. Hematite 
occurs plentifully in bands in quartz veins which have not been shown to contain gold. It 
is possible, however, that they are related to the gold veins. Magnetite occurs in the wall 
rock of a quartz vein at the Jones tin mine and has undoubtedly been formed by the vein 
solutions. This is another link between the Jones vein and the Dahlonega veins, in which 
magnetite crystallizes with the quartz. The occurrence of cassiterite at the Brewer mine 
is noted on page 91. 
CONCLUSIONS. 
The character and association of many of these minerals are unusual and nearly all 
indicate that the deposits are of deep-seated origin, having been formed under great pres- 
sure and at high temperature. 
t 
DISTRIBUTION OF THE GOLD. 
GENERAL FEATURES. 
The subject of the distribution of the gold in the veins and in the replacement bodies is 
of the greatest practical importance. It is regretted that information on this point is so 
meager. In many cases development has not been sufficient to furnish good evidence, 
and on the other hand deduction from the form, size, and position of stopes is not satis- 
factory, for they indicate the distribution of only such ore as could be profitably mined 
under conditions existing at the time they were made. 
It may be said, however, that the distribution of gold in the deposits is in general irreg- 
ular. Some veins or ore bodies seem to be of fairly constant grade, but pockets, pay shoots, 
and relatively rich lenses within the main deposits are the general rule. 
In the veins ore shoots, usually of rather small cross section and of steep pitch, afford the 
most profitable places for exploration. Where the veins are richest the surrounding altered 
rock likewise generally contains most gold, but everywhere less than the vein, so far as 
known. Rich ore is usually accompanied by much pyrite, but there are numerous 
exceptions to this rule. 
In the replacement deposits the bodies of pay ore are large lenticular or ellipsoidal masses, 
with gradually decreasing values toward the exterior. In a few instances the change from 
profitable to barren ground is so abrupt that the deposit may be said to have a wall. Within 
these large bodies the value is not uniform. The best ore generally occurs where most 
silicification has taken place, and this also in many cases corresponds with the degree of 
pyritization. At the Haile mine comparatively rich ore is generally found in those places, 
among others, where molybdenite occurs with abundant pyrite. 
The cause of this concentration of gold in certain places or along certain lines has not yet 
been ascertained. In some cases it is believed that the presence of cross fissures has been 
influential, but definite proof can not be brought forward. In the case of the replacement 
deposits at the Haile and Colossus mines it has generally been considered that the diabase 
dikes which cross the ore bodies have been the controlling factors in ore deposition. This 
subject is further considered under "Genesis of the deposits" (p. 68), but it may here be 
stated that careful examination has failed to reveal any genetic connection between the 
diabase and the gold. Moreover, the fissures through which the diabase dikes were later 
intruded seem probably to have had no connection with the original deposition of the gold. 
SECONDARY ENRICHMENT. 
All students of ore deposits recognize that several of the metals are dissolved by surface 
waters and are reprecipitated in the upper portions of the deposits by the process commonly 
known as secondary enrichment. It is the general opinion, however, that in the case of gold 
the solubility of the metal is so slight that this process is of little consequence in enrichment 
from the commercial standpoint. The importance of secondary enrichment in certain gold 
Bull. 293—06 5 
