BREWER GOLD MINE. 91 
much decomposed into sericite. Dark grains of a nonmagnetic titanium mineral are closely 
associated with this fluorine mineral. They may be ilmenite. . Pyrite is present in crys- 
talline grains impregnating both constituents. These less altered portions are practically 
valueless and have been left in place as the ore has been mined away from them. They 
are known as dikes. In all cases observed, however, they have no distinct walls, but grad- 
ually pass by increase of shattering and silicification into the dense bluish rock which con- 
stitutes the ore. On the surface this silicified ore is stained red from oxidation of the iron 
and well shows its brecciated character. Narrow veinlets of quartz, carrying a little pyrite, 
cut both the highly silicified and the little altered rock. In the former they seem to fade 
off into the surrounding rock; in the latter their walls are distinct, and along with and 
close to the pyrite they hold radiating masses of pyrophyllite. It certainly appears as 
if the three minerals — quartz, pyrite, and pyrophyllite— were contemporaneous. 
Granite is known to occur about three-fourths of a mile to the west. It is said that 
a diabase dike passes near the mine. 
From the standpoint of the miner the Brewer ore is similar to that of the Haile and 
Colossus mines. It is a dense blue siliceous ore, carrying finely disseminated pyrite and 
a variable amount of free gold. The ore of these other mines, however, is a replacement 
of bedded tufts, while the Brewer rock is a replacement of what is probably only a massive 
igneous rock brecciated in place. There is consequently no evidence of bedding nor 
banding, and the only structure which the deposits show is a number of rather irregular 
systems of joints. The most prominent jointing strikes about N. 70° E. and dips steeply 
to the northwest. The Brewer ore is also more siliceous than that from the Haile and 
Colossus. Although pyrite occurs in the unsilicified rock, it carries very little gold. The 
pyrite in the blue, silicified rock, which averages about 7 per cent of the total mass,a carries, 
on the other hand, both gold and copper. When the pyrite decomposes it leaves cavities 
lined with an iridescent film of limonite. A black copper arseno-sulphide, enargite, is 
also present in small crystals and separates in the gold pan as the so-called " black sand." 
Where oxidation has taken place, this arsenical sulphide is decomposed and the copper 
is converted into the sulphate, chalcanthite, which forms a blue coating on the walls in 
several places, particularly at the north side of the main pit. Covellite has been found 
in the ore b and bismite and native bismuth have been reported, c Cassiterite has been 
found at this mine/* sometimes, as reported, in close association with the gold.e It seems 
probable that the cassiterite is an associate of the fluorine mineral of the original rock 
and that the ore, brought in later, was deposited about this difficultly soluble mineral. 
The siliceous cement which binds the silicified fragments into a dense rock has been 
much attacked by surface water. Along certain planes or lines the cement has been 
removed by solution, allowing the rock to crumble to a very fine white powder which is 
almost pure silica. All the sulphur, iron, and copper of the sulphides have been leached 
out, but the gold remains, doubtless as free gold. Within these soft sandy portions residual 
masses are often found. They are hard and many of them when broken open are found to 
have a blue, unaltered core containing pyrite. In numerous instances they assume fantastic 
nodular forms resembling those of certain concretions. This sandy ore is especially sought 
! for by the miners. In the first place, it is perfectly free milling. Moreover, it is of better 
J value than the average blue unoxidized ore. This difference in value may be partly 
j explained by the fact that the proportion of gold in the sand has been increased by the 
I removal of such material as has been dissolved away. But this seems hardly adequate 
ij to account for the marked difference in value which is said to exist. The residual lumps 
.'] of unoxidized rock found in the midst of the sand are said to be decidedly richer — they 
I certainly hold more pyrite — than rock of similar appearance from the large unoxidized 
oNitze and Wilkens, Bull. North Carolina Geol. Survey No. 10, 1897, p. 144. 
b Becker, G. F., Gold fields of the Southern Appalachians: Sixteenth Ann. Rept. U. S. Geol. Survey, 
pt. 3, 1895, p. 279. 
J c Tuomey, M., Geology of South Carolina, 1848, p. 97. 
■ d Clarke and Chatard, Am. Jour. Sci., 3d ser., vol. 28, 1884, p. 25. 
e Becker, G. F., op. cit., p. 308. 
