Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1880-07-11
CLASSIFICATION OF ORE DE.
POSTS.
An Interesting Paper by Professor
Newberry.

An Interesting Paper by Professor
Newberry.
Professor Newberry has recently con-
tributed what the Engineering and Min
ing Journal terms o very able and enter
tanning paper on the subject of the CLASH
fcation Of ore deposits. Our Ruby Hill
mines are treated under the head of
I" chamber mines" We have not been
favored with a copy Of Professor New
berry's paper, but find a criticism on il,
presumably by Professor Rossiter W.. Ray
mond, in the Engineering and Mining
Journal Of July Sd. We append hat por-
ton Of the criticism relating to the mines
Of Ruby Hill, as follows:
Returning to the explanation given by
Prof. Newberry Of the formation Of cham
ber-mines, we have but one criticism to
make upon it. Prof. Newberry's sweep
ing statement that the limestone carrying
such deposits has at some time been
honey-combed by chambers and galleries,
and subsequently broken through and up
heaved, permitting the entrance Of ore
into assures thus formed, goes too far. He
says at has been suggested that the
caves now holding ore were excavated by
the metalliferous solution but we find
some of them entirely empty, with their
sides incrusted with spar, and having all
the characters Of ordinary limestone caves,
and even where the ore occurs, the walls Of
the cavity have the same character, are
hard and u~nimpregnated with ore. Hence
we must conclude that the chambers were
formed, like modern caves, by sur
face water; and when the country
was upheaved and the rock shat
tered, only part Of them we're opened, and
that these received the solution and ore,
while the unopened ones remained empty"
Among the mines which he cites as types
OF this class are those of Eureka; and
without questioning his conclusions as to
mines which we have not personally
studied, we must take leave to say that the
description we have quoted does not agree
with the facts presented at Eureka. The
mines of Ruby Hill do not contain entirely
empty caves; and the limestone Of the
cave-walls is not solid, but crushed, fis-
sured, and recemented. Moreover, the
unquestionable proof of the tremendous
crushing OF the zone Of limestone con-
tanning these ore-deposits renders it incon-
ceivable that caves previously formed in
this zone could have survived. The lime
stone has been squeezed out at some places
till there is not half an inch of it.; and the
material thus compressed has been showed
upward, widening the zone toward the SUR
face, until at the outcrop it covers nun
dreds of feet. To conceive that a body of
rock subjected to such pressure could con-
tinue to carry caves Of a hundred or more
feet in diameter, is beyond our power.
The force which solid limestone was unable
to resist could not be resisted by a hole.
But it is not necessary to believe, in this
case, that the caves were excavated by "the
metalliferous solution" if by that is meant
the original solution which deposited the
sulphides. In the Eureka mines, this
original solution evidently penetrated the
whole of the crushed limestone zone;
and the subsequent accumulation OF oxi-
died ores in the caves and assures,
tending toward the footwall Of those
mines, is plainly the result Of secondary
action, oxidizing and redistributing the
ores. This secondary action is due to sur
face water percolating downward; and it
must be confessed that the conditions of
this particular limestone body, after its
upheGsal and after the exposure of its i'm
mense outcrop, were more favorable to the
reactions to which Prof. Newberry justly
ascribes cave-formations than any probable
previous conditions would have been.
Moreover, the position and shape of the
caves and ore-bodies, tending in depth, we
believe without exception, toward the foot
wall quartzite, indicate that they were
formed by downward percolation, after the
~upheaval. This relation to the foot-wall
has proved an important guide in explor-
ing for new ore-bodies.
That ores such as these mines originally |
contained, namely, arsenical pyrites and
galena, can not be transformed through
the agency of surface waters into iron
oxide, carbonate, sulphate and a~rseniate of
lead, without some redistribution, is a
MISUNDERSTOOD principle. 1t follows from
the increase in the bulk of the ores so
oxidized, and the more or less soluble
character Of products of the oxidation.
We do not doubt that there may be de-
posts of this class which answer Professor
Newberry's description. But the Eureka
mines, as he would probably admit upon q
closer consideration, do not, in the one
particular we have mentioned, bear him
out.