Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1886-03-11
EUREKA
what nm Important Work Has 10
Say of Its Mines. Their Forma-
ton. Etc.

Say of Its Mines, Their FOrma.
tiOn, Etc.
The SENTINEL is just in receipt OF Vol.
10 of the Tenth Census of the United
States. which is devoted to statistics and
technology Of precious metals. The work
was prepared under the direction OF Clar-
ence King. and published in the Govern
ment Printing Office at Washington, d.
C. II is full of practical information con-
corning the mining sections OF the West,
and especially Nevada. We copy a portion
| OF what it has to say of the mines OF Eu-
| reks District, knowing that 1t will be Of
general interest to the SENTINEL's readers:
The ores OF Ruby Hill are argentiferous
| galena, accompanied by its decomposition
products. Indeed, tho larger part OF the
ore thus far mined is carbonate, mixed
with some sulphate and ocher, as we'll as
with mimetite and wulfenite, the occur
renee of which indicates the presence OF
considerable quantities OF other metallif-
erous mineral besides galena prior 70 de-
composition. The ore bodies are lrregu-
lar, kidney-shaped masses distributed in
limestone. This rock, though highly
me~tamorphosed, is distinctly stratlhed IN
parts, and has been proved by Mr.. Haynes
party TO carry fossils which determine its
age as Cambrian. The nature OF these
ore deposits has formed the subject OF re-
peated lawsuits, and the many well-knowD
geologists and mining engineers who nave
given testimony on the subject have ex-
pressed very discordant views, some hold
ing them to be pipe veins in the limestone,
while others regard the whole limestone
formation between the quartzite and the
shsle as ore-bearing, the barren portions
answering to the bone in coal seams.
While the one party consider the small
seams of ore sometimes found connecting
the ore bodies as the rake vein correspond
ing to the pipes, the other party attributes
these seams to the accidental presence OF
f~issures, and ascribes no significance to
them. The diversity OF opinion devel-
oped as regards the deposits of Ruby Hill
appears to indicate merely that large imam
ciaI interests are involved in the title to
this property. and not that there is any
thing exceptional in the character OF the
deposits themselves. Lead ores are more
often found in limestone than elsewhere.
and when so found almost always exhibit
great irregularity in form and distribu-
ton. The fact is that little is definitely |
known with reference to the modus oper.
andi of the deposition of galens. As
Mr.. Emmons, in discussing the deposits
of Leadville, has pointed ont. il the by
pothesis often advanced that this ore has
been deposited in pre-existing caves were
correct concentric structure would neces-
sarily result. He regards it as more
probable that the ore has been deposited
by substitution for limestone. If this
- lo-p aono1,otvolv laad dannuitS l
OF this character would have to be re-
garded as veins differing from the usual
type merely in the extreme irregularity
OF the walls; for an ordinary vein Is
merely an opening in the rocks, which is
always limited in horizontal extent, and
probably also in depth. Into such a fis-
sure metalliferous solutions percolate and
deposit ore minerals, precipitation being
due TO chemical or physical causes.
Usually the walls OF veins are chemically
inert, and hence do not lose their orig
inal form; but If the substance OF the
walls of q vein, instead OF Q. g., inhltra-
tions OF organic matter, were to induce
precipitation, that fact certainly would
not deprive the resulting deposit OF it's
character as a vein, though the shape OF
the walls might be strangely modified.
A very remarkable feature of the Eu-
reka deposits, shared to a greater or less
degree by many others in the Great
Basin, is the great depth to which de-
composition, involving an accession OF
oxygen, has proceeded. The mines are
between 1900 and 1900 feet deep; yet,
although some water has been met of
late, the permanent water-level has not
been reached, and the amount of galens
in the ore is scarcely more than enough
to prove that the original lead mineral
was the sulphide. The conversion of
the galens 10 carbonate and %sulphste.
which must clearly be ascribed to the
agency of atmospheric oxygen. could take
place to such a depth only in an ex-
tremely dry country such as the Great
Basin now is, and the decomposition
must therefore have been accomplished
since the early qusternary.