296 
GEOLOGY. 
they are in small quantity. Veins of crystallized carbonate of lime traverse the cinnabar, and 
fault the small beds and strings of the ore. Bitumen is occasionally found associated with the 
calcite. 
The mines and works are under the able superintendence of Captain H. W. Halleck, formerly 
of the United States engineer corps, and he has introduced many improvements. A large 
tunnel has been cut in on the side of the mountain, and a wide track laid, on which cars run in 
to the centre of the works and are loaded with the massive ore. On reaching the surface it is 
assorted, weighed, and packed upon mules, and thus transported down the mountain to the 
works for the extraction of the metal. 
From the descriptions given of the ore and mine of Almaden, in Spain, it would appear that 
there are many points of similarity in the two localities. The vein at Almaden is described as 
very thick, and composed of massive cinnabar. It is also reached by a tunnel. 1 The furnaces at 
New Almaden differ from any in use elsewhere., and are very simple and effective. The large blocks 
of ore, and rock containing it, are not crushed, but are piled loosely together in a brick chamber, 
as if they were to be roasted. The flames from an exterior fire are made to pass through this 
chamber and the ore ; and the products of combustion, together with volatilized sulphuret, pass 
on through a series of chambers until the separation of the sulphur and the mercury is com¬ 
plete, and the metal is condensed. The smoke, sulphurous, and carbonic acids escape through 
a tall chimney. In this process the sulphur appears to be oxidized by the free oxygen which 
passes through the fuel. No lime is used, and there is no necessity for crushing the ore ; it is 
an exceedingly simple process, but is adapted to that peculiar ore only. 
Some, idea of the amount of quicksilver which this mine produces may be obtained from the 
record of the amount exported from San Francisco—all of it the production of the mine, but 
exclusive of the large quantity used in the State. This, in 1856, amounted in value to $831,724. 2 
GOLD. 
The route followed by the Expedition passed within a few miles of the great auriferous quartz 
veins of Mariposa county, and, for a part of the time in that vicinity, over earth which would 
doubtless yield gold if prospected under favorable circumstances—water being very scarce. We 
were also at one time very near a mining town called Quartzburg, so named from the number 
of the quartz veins in the vicinity, and the mills erected there for crushing the quartz and 
extracting the gold. 
This region appears to he peculiarly rich in huge quartz veins, or “dykes” and “ ledges” as 
1 I copy the following notice of the Almaden mines from the Journal of the Geological Society of Londm: “These 
mining works were known to the Romans. A long, tunnel-like gallery, the Socabon del Castillo, lined throughout with 
freestone, roomy enough to admit of carts with two horses abreast, and furnished on both sides with granite foot-ways, 
passes from the flat valley, at the southern side of the ridge, on which Almada is built, into the mine ; the whole town is 
undermined. From this tunnel many other passages are cut into the clay-slate, which is the matrix of the ore, one of 
which opens into the Boveda de Santa Clara, a dome-shaped hall, fifty-one feet high, and forty-two feet broad. Here for¬ 
merly stood a horse-winch for the removal of the ore. The workings reach a depth of 1,140 feet. The cinnabar vein, 
with a strike east and west, and a nearly perpendicular dip of from 60° to 70°, has an almost fabulous hulk. In the first 
story, of which the mine has nine, the vein is eighteen feet strong ; in the lowest it is 60'. The spectacle of this colossal 
vein of ore at the working places is gorgeous, from the dark-red color of the cinnabar, which appears sometimes earthy, 
sometimes in dense masses, and sometimes even finely crystallized. Dispersed through it are calcspar druses, and at many 
places small holes and clefts are filled with pure quicksilver.”—(Jour. Geol. Soc. London VII, 1850-51. Translated from Leon¬ 
hard U. Bronn’s iV. Jahrb. F. Min. W. S. IF., 1850, 4 H , p. 497 ; and Bergwerk'sfreimd, 1849, Mill, p. 72, et seq. 
2 Report on Commerce and Navigation for 1856, page 340. 
