Tonopah bonanza. [volume] (Butler City [i.e. Butler], Nev.) 1901-1909, 1904-05-07
THE FORMATION
OF GOLDFIELD
Professor Spur Writes Of
Its Economic Conditions.
Geographically the New District Re-
SembIeS the Silver Peak and
Belmont Country.

Interest has been aroused in the
new camp of Goldfeld, E%smeralda
county, Nevada. This district is sit
uated 239 miles southeast of Tonopah
and about six miles due east Of the
old mining camp of Montezuma.
Recently some good values in gold
have been found; several hundred
people have gone there, and ore has
been sacked for shipment from some
of the mines.
The writer visited this district in
June, 1903, shortly after it had been
located, and while only a few men
we're working. Some COON assays
had been reported at this time, while
other attempts did not succeed in
finding much oyer a trace Of gold.
The district then was known as the
''Grandpa," but the name has since
been changed. The writer's visit
was a flying one. and 40 close exam
ination was made, but such notes on
the geology as were taken may prove
of interest.
GENERAL GEOLOGY.
geographically the district shows
a number OF low ridges. To the west
are basalt- capped mesas, leading up
into the higher mountains in the
vicinity of Montezuma. The part of
the district examined consists of one
of the ridges mentioned, which runs
in a north-south direction; this was
followed for a distance of about two
miles. On the north end Of the ridge
the rock is a very much altered rhy-
olite, showing strong flow structure,
a CLASSY ~groundmass, and porphy-
rite crystals of quartz, orthoclase,
and biotite, which are, however, al
most always decomposed. Near the
north end of the ridge the igneous
rock is chiefly alaskite (quartz-feld-
spar ROCKY, sometimes of granite
structure, sometimes coarse and
pegmatitic, frequently very fine
grained. A variation Of this is
quartz muscovite rock which, when
fine grained, resembles somewhat
metamorphosed quartzite. Some OF
these quartz-muscovite rocks seem
to have been originally such, while in
other portions the muscovite seems
to have formed in little blades at the
expense of original orthoclase field.
spar. A process OF endomorphism
similar to that described by the
writer in similar rocks at Belmont,
is suggested; and since muscovite is,
like ~orthoclase, essentially a silicatt
Of aluminium and potassium, but, un.
like it, usually contains a weighablt
amount of huorine, the action of this
gas is probable. In one of the thir
sections a crystal Of probable huorit'
was detected. Another variation i
pure quartz, which occurs in tn,
alaskite in small blotches, lenses, ant
even in masses two to four feet il
diameter. All these are intrusiv
into a dark siliceous rock Gasperoid)
which is probably the result Of tn
s~iliciication of an original limestone
By analogy with the similar geologi
conditions in other districts in tn
same general region-as at Silve
Peak and Belmont-we may suspec
that the limestone is of Cambrian o
Silurian age, and that the alaskit
may be correlated with the graniti
rock intrusive into the limestones !
those districts.
The relation between the rhyolit
and the alaskite is uncertain. Som
phases OF the alaskite are not distir
guishable in the hand specimen fror
the rhyolite, and since they hav
about the same composition one
tempted to consider the hypothesi
that they are differently crystalline
portions Of the same magma; but tn
strong flow structure of the rhyolit
and its usually CLASSY groundmass il
dictate that, even If this is SO, the
we're formed under different cond
tions and at different times, and tina
the rhyolite was formed near til
surface, the alaskite at a consider
able depth.
A%URIFERoUs VEINS.
The chief veins or ore bodies bein
prospected at the time of the writer
visit are broad masses of white
purplish and reddish, iron-staineC
cherry quartz, extending IRREGULAR
in a northerly direction IN. 10 dee
to Is deg. W.. There r usual
no well defined walls to these, an
the width OF the mineralized zone
varies from many feet in one place I
nothing in another. AS reported
they assays made up to that tim
are very irregular, some averag
samples giving $25 to $50, other
only a trace. The values of thes
are all in gold, very little or no silve
being present.
When examined under the micro