The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1905-04-21
The GOIdfield Mining District
By Charles J. Moore, Mining Engineer
As usual, the new conner mas scarcely
Copyright Applied for by chas. J. MOore)

as usual, the new conner HAS scdiCeis
been "a hours in this district before he
is asked his opinion. The writer has
been here now for seven weeks and still
finds much to learn in spite OF many
trips through the various sections with
in a radius of six miles north, east and
south of town.
The geology is interesting and differs
from that of most other mining districts.
1t has been written up already so much
in good, bad, or Indifferent opinions,
that another added to the list cannot
tell much that is new. What the in
vesting public wants to know is not
scientific facts or individual opinions so
much as whether the facts so far as as
certained by developments justify the
general opinion hat this district is a
safe field for investment, and that the
geological facts Indicate continuity to
the ore bodies, any increase or decrease
in values as depth in the veins is at
tanned, and whether there is a long life
before the district for the future, or
whether it will be ephemeral like so
many Nevada mining districts in the
past.
This region is entirely volcanic and
is similar to Tonopah in exhibiting
surface flows of various rocks, chiefly
rhyolite and andesite. These rocks
which form the main mass OF the country
are intersected by numerous dykes of
rocks belonging to the same classifica-
ton as the general country, but of later
geologic date, and for the most part
highly silicifed, or altered in many
cases completely into quartz. That is,
the rhyolite and andesite dykes are thus
greatly silicified, but the basalt or dia-
base dykes which are much fewer in
number than the others are apparently
of considerably later date than the
quartzose dykes or lodges, and have es-
capped any siliceous metamorphism.
They appear to have been extruded after
the period of vein formation or mineral
ization, and this accounts for their bar
rem character SO far as / have observed
them.
As a rule, the veins follow the course
of these silicified lodges throughout the
district. Though there are probably
many veins yet to be opened OF economic
value which are not directly associated
with one of these dykes, yet almost all
those now producing payable ore in the
district are thus associated, the vein
sometimes being in the heart of the
ledge, sometimes on either side OF the
same, sometimes cutting diagonally
across the same. Occasionally, the veiI
and dyke are a short distancv.apart and
running parallel, or the vein has sucl
a course as soon brings it again in CON
tact with the dyke when followed
lengthwise.
Mr.. Spur, the e.. S. g~eologist, who
has visited this district twice, considers
these siliceous or quartzose outcrops on
the top of the low hills or ridges so mum
erous in the district, to be the siliceous
envelopes of elongated vents or chin
neys of hot springs. While this il
doubtless true of many it is not univer-
sally so, as will be readily understood
from the statements above. The genesis
or origin OF the veins and valuable con-
tents is from below. not from any previ-
ously everything rocks which have long
been eroded and carried away, nor from
any OF the present country rocks at
slight depth below the present surface,
as none of these shew evidence of any
such metallic minerals as are found in
the deeper workings OF the Combination.
Florence and Quartzite mines.
The history OF the Goldield volcano is
quite different from hat eff Cripple
Creek, Colorado. The latter comprises
one central crater the seat of violent eX-
plosive outbursts of rock fragments, va
rying in size from pinheads to boulders
feet in diameter, very much dust and
very limited flows of molten lavas.
These f~ragmentary rocks and volcanic
dust were eventually consolidated into
secondary rocks becoming the andesite
breecia and tufa which form the main
mass OF the country in the Cripple Greek
district today covering an area Of some
what less than 20 square miles. In this
area are one or two minor vents clearly
indicated by local differences in the adj
jacent country, but none OF which with
one exception, that neal the Gold Coin
mine) had any effect in the later min
eralization. At the conclusion OF the
volcanic outbursts. the final thr0es crea-
ted numerous assures having a general
northerly or nOrthwesterly course
throughout the region, and some of these
were filled later by ~phonolite dykes,
some by quartz veins and some by ba-
salt dykes, which in point of time APP
peared later than the phonolite but be-
fore the vein formation.
A distinct popularity of the Cripple
"a