The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1904-10-14
GEOLOGY OF %cOLDFIELD.



aida county, Nevada, east of the Cali
fornia state line, holds the attention of
the mining world at present. The claims
of that region to p~henominally rich dis
~coveries of gold have been the subject of
much discussion pro and con
A. Leslie Curtis, member of the Insti-
tute of Mining Engineers and a mining
engineer of practical experience, has
prepared for this paper a study OF the
geological conditions of the region, which
is herewith given.
The mining camp of Goldfeld is stu
ated about twenty-six miles south OF
Tonopah, in Esmeralda county, Nevada /;
it is attracting much attention in min
ing circles from the abnormal richness
of its ores and the great results that have
been demonstrated during the short life
of the camp.
Much has beer written relative to the
geological structural formation of the
district which is very simple. The pre-
dominating formations are an1esite,
rhyolite, porphyry and intrusive dikes
of quartzite. The strike of the outcrops,
or iron blowouts, is northeast.by south
west. The term blowout as applied
to the Gaping or gossan, or ferruginous
calcite ~'limonite," or granular silica,
conglomerated by iron, is a misnomer,
as it argues the easily disproved igneous
theory of veins of injection, meaning
thereby that the quartz with metallifer-
Gus contents was thrown out in a molten
state from the interior of the earth.
This has in no case occurred and the
theory is impossible. True lodes are
veins of injection formed by the infltra-
ton of silicated waters carrying the
metals also in solution. This water
filed the assures caused either by the
cooling of the earth's crust, or formed
by sudden upheavals of the igneous
rocks.
There is a pregnant Cornish saying
with regard to mining: ''The iron hat
covers the golden head" Mining in
Goldield has verified the truth OF this
aphorism. Where the erosion of the
rhyolitic flow is most in evidence, the
number of flows it is impossible to de-
termine, and is of little importance to
to the practical miner or capitalist, who
are more interested in the commercial
possibilities of their properties than in
the intricacies of the dispositions of the
Silurian or Cambrian systems, the I'M
DERIVING porphyries are the auriferous
bearing rocks.
Work sufficient has peel lone in Ton
opah and also in this camp to prove be-
yond any doubt the continuity and per-
~inanency OF the ore deposits. The con
ditions g~eologically in Tonopah are
more complex han in Goldield, but
the practical mining engineer, not the
expert who infests and afiiicts the gold
mining camps of the world, who draws
his deductions from what practical min
ing has demonstrated under similar on
ditions, finds that Tonopah and Gold
field are parallels to other great mining
camps.
1t was stated in the early days Of Ton
opah that 'there were no mines there,
the conditions were not right" The
Cornish miners saying with regard to
metals generally is very forciblc:
"Where it is, there it is" and Cousin
Jack adds, with pathetic emphasis, land
where it is generally, there | amt"
The pessimist has been busy ventilat-
!, ing theories regarding the future OF
, Goldfeld and Tonopah. Mining history
repeats itself. All the great productive
camps Of America were knocked" and
invariably by persons who had an ul-
terror object in view. "Will the veins
fown?'i They will undoubtedly not
o up.
A few facts relative to the deposition
of gold ores cleaned from-Many years
! practical experience in gold camps may
proz-ssHaeqest-
The question as to how gold was orig
in Nv deposited in our auriferous veins
is one l. which u large amount OF atten-
ton has been given both by mineralo-
pists and practical miners, and which
has been holly argued by those who
held the igneous theory and those who
pronounced for the aqueous theory. 1t
was held by the former that as gold was
not probably existent in nature in any
but its metallic form, therefore 1t had
been deposited in its siliceous matrix
while in a molten state, and many In
g~enious arguments were adduced III
support OF this contention.
OF late, however, most scientific men,
and indeed many purely empirical in
.qnirers have come to the conclusion that
though the mode in which they were
com posed was not always identical, all
veins, or lodes, including auriferous for
smations, were primarily derived from
mineral impregnated waters, which de-
posted their contents in assures caused
either bv the cooling of the earth's crust
or by volcanic gency.
Recently published opinions contend
that gold is not found in the products OF
!, volcanic action. The person making
this premises as his theories do not hold
good in the great mining camps OF Amer
lea, where gold is often or more usually
found at, or near, either present or past
regions Of volcanic action. Deposits
NAV be found in many regions and in
many kinds Of rocks, but mainly in
mountain regions, and in ~metamorphic
and igneous rocks, because the thermo-
sphere is nearer the surface, and ready
access thereto through great assures, is
mostly found in these regions and in
these rocks.
These views are in accordance with
nearly all modern research into this in
teresting and fruitful subject.
During my visit to the mining camps
OF Tonopah and Goldfield, through the
courtesy OF mine owner n lessees l
vas permitted to examine, and make
tests OF ores, etc.
The possibilities of the major number
OF mining properties are abnormal. In
many parts of Tonopah and Goldield |
noticed the conveyance or junction OF
veins, where no work had been done. 1t
rshould be borne in mind that at such
places the vein is invariably more richly
metalliferous han n%eighboring parts,
probably because there the deposlting
reagents met. The explanation OF this,
i think, is simple, on the aqueous theory
of filling of lodes. The water which is
t.aversing two different channels Of me-
cessity passes through different belts OF
country, and will thus have different
minerals in solution.
The result of these two waters meet
E-N@