Gold Hill daily news. [volume] (Gold Hill, N.T. [Nev.]) 1863-1882, 1865-11-11
The Mechanically OF the Comstock
LOden. -T.HHf .'IF .H .

ANOoCAs ".. ..N
One Of the most important lessons OF
mining experience, taught by all the princi-
pal authorities, is that the true 6ssuro lodes
are continuous geologically and inexhaust-
IDLE practically, although a point may be
reached where the extraction Of ore ceases
to be profitable. A true vein, according
to Professor Whitney, is "a assure in the
solid crust Of the earth Of indefinite length
or depth, which has been filed more or
less perfectly with mineral substances; or
in other words, an aggregation Of mineral
matter, accompanied by metalliferous ores,
within a ~crevice or assure which had its
origin in some deep-seated cause, and may
be presumed to extend for an indefinite
distance downwards." According to the
theory accepted by biologists generally,
the 6ssure was made by some internalcon-
v~ulsion, and while it stood open it was
filed up with the veinstone, the ores COM
ing up in vapors from the intensely hot
regions below, and crystallizing or con-
densing in the vein. This theory implies
continuity in the vein, and ineShaustibiity
in the mineral. The assure veins always
have q veinstone differing in geological
character from the walls, which are usu-
ally distinctly marked. Thickness Of
lode, steepness of dip, distinctness and
hardness of wall-rock, difference in char
ac,er Of the two walls, difference in char
acter Of wall at different parts Of the vein,
occurrence Of horses similar in geological
character to the hanging wall, and clay
seams that appear to have been formed by
the grinding Of the veinstone against the
walls, are all important evidences Of a true
assure vein. All these evidences are found
in the Comstock lode, the wall Of which is
y hornblendic porphyry on one side and a
felspathic porphyry on the other, accom-
panied in places by trap. The ~felspathic
porphyry is found in the vicinity of most
Of the great silver lodes, and its presence
as a wall-rock is considered a most favor
able indication of the continuity of the
vein in Spanish America.
All the great silver lodes now produc-
ing any considerable amour of metal, are
considered to be true assure veins. The
mines at Cerro Pasco, in Peru, have been
worked since 1913, yielding $3.50, 000, 900,
and are still productive. The Potosi
mines, opened in 1915, have contributed
ST. 900, 900. 900 to commerce, and are not
yet exhausted. The mines Of Guanajuato
and Zacatecas have been worked about
three centuries, and together they have
yielded more silver than Potosi, and they
are still among the most productive of the
world. Alamos, in Sonora, has been an
important silver mining district for two
hundred years. The mine of Guadalupe
Calvo, in chihuahua, though it has been
worked thirty years, yielding in som
years as much as $1,000, 900, is not yet
abandoned. The mines Of Sombrerete,
discovered in 1870. were worked with
great profit, one of them yielding 800, 900
per day for Ave years, until 1898, when
they were closed by a lawsuit and then
rendered inaccessible by the accumulation
Of water. Thus they remained for nearly
one hundred years. until a bold man came
along. re-open,d them, and took out in a
few years Sl3, 900, 900 and the mines are
still considered to be rich. Santa Eulalia,
in chihuahua, was worked for eighty
years, and was then abandoned, not be-
cause Of exhaustion. but on account of the
hostility Of the Indians. Chanarcillo, in
Chile, has yielded about 8 1000, 900 annu-
ally, for more than thirty years, and no
one anticipates any interruption Of its
productiveness in our time. Real del
Monte is rich to-day, though it has been
prominent for its production of silver since
the middle of the sixteenth century, with
no interruptions saw those caused by
water and the want Of drain tunnels. The
silver mines Of Hanover and Saxony are
not exhausted, though they have been
worked since the middle ages. Nine-tenths
of the silver yield Of Spanish America and
Europe comes from veins that were open
ed more than two hundred years ago, and
have been profitable ever since. Not one
of them has the features Of continuity
more strongly marked than the Comstock
lode, and few Of them promise to yield
more silver. Some are wider, others have
been traced farther. and others have richer
ore, but no other has produced $50. 600, 600
within three years, or has been worked
with so much energy, or offers such facili-
ties for deep draining, ventilation and the
extraction Of the ORES. F. Alta. w 90"