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 "T 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. Itis also reached by atunnel. The furnaceg 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." 
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 be peculiarly rich in huge quartz veins, or ۴ dykes” and “ ledges,” 
These‏ 4 ه 
odi with‏ 
as 
1 I copy the following notice of the Almaden mines from the Journal of the Geological Society of London 
mining s were known to the Romans. A long, tunnel-like gallery, the Socabon del Castillo, lined throug 
nn roomy enough to admit of carts with two horses abreast, and furnished on both sides with granite foo 
m the flat valley, at the southern side of the ridge, on which Almada is built, into the mine ; the whol 
underm ined. From this tunnel — other passages are cut into the clay- slate, which is the matrix of 71 Hore f 23 
merly Mond a horse-winch for the Beine of the ore. The w each a depth of 1,140 fee 
with a strike east and west, and a nearly prd dip of Mac xe "i 709, has an almost hash bulk. 
story, of which the mine has nine, the vein eighteen feet strong ; in the lowest it is 60 The spectacle o 
vein of ore at the working places is gorgeous, en the dark-red color of the cinnabar, which appears sometimes es Ze 
sometimes in dense masses, and sometimes even finely nitrum ized. Dispersed through it are calcspar druses, and = vd 
places small holes and;clefts are filled with pure quicksilver.’’—(Jour. Geol. Soc. London VII, 1850-51. Translated fr 
hard U. Bronn’s N. Jaarb. F. Min. W. S. W., 1850, 4 H , p. y and Bergwerk s freund, 1849, XIII, p. 12, ۰ 
? Report on Commerce and Navigation for 1856, page 340. 
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