The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1905-05-12


2lst, found sufficient to disagree with, to
furnish the following notes. The com
munity will probably stand a little more
embryo geology, till such time as Mr..
Spur with his great experience, and
opportunity presented by the u
of the L. :. Geological Survey, shall set
all right, at least on the aerial features.
While having been here about the
same time as Mr.. Moore, it has no been
my privilege to examine any of the larger
older mines underground. The rock
names herein used are merely field de-
examinations.
Leaving out the congratulations and
Cripple Creek matter in Mr.. Moore's
article, the main points stated are:
First-That the ore veins are assc-
Grated with silicified dykes, either rhyo-
lite or andesite. A dyke implies a fis-
sure filling of volcanic rock, of later age
than the enclosing country. 1t is aues-
tionable whether such occur as specified.
In the Jumbo, Combination, January,
Red Top, Florence and st. Ives, the sup
posed dykes are silicitied reefs of coun-
try, along lines of fracturing. The same
may be said of the Cracker Jack and
contiguous claims, and OF the Kendall,
Sandstone and Desert Rose. In the
body of this article reference is also
made to many more places in the dis
trict, with the same phenomenon. The
practical difference to the miner in the
two views, lies in the fact that aAdyke
OF later rock would be easier to follow
than mere assuring. If the reefs are
altered phases of the country rock. they
are likely to be less pertinacious than
dykes. as the silicification will give out
at intervals, and nothing will be left but
more or less decomposed country along
the fractured planes, while dykes are
expected to stand somewhat like walls
with great continuity. Even dykes of
TIE same character as the country, an
desite in andesite, and rhyolite in rhyo-
lite, would proably be slightly different
INTERNATIONALLY and in texture from TIE
enclosing walls, and easy to follow. 1t
is, therefore, important for the miner to
know whether his vein CD is a silicitied
reef of country or a dyke. Mr.. Spurs
characterization of them as siliceous en-
velopvs of elongated vents or chimneys
Of hot springs, would, in my view, be a
correct definition.
Second-That the ores We're deposited
by ascending waters, and derived their
values from d~eep-seated, and not from
everything rocks. This seems unques-
tionable. Mr.. Moore differentiates, as
does the writer, bet Seen the action
causing the primary siliciication exist
ing the secondary slight silicification at
tendant upon the ore bodies, it suggests
a case of secondary concentration of the
precious values by ascending waters.
Attention may here be called to an in
teresting and final stage of solfatarism
in the deposition OF carbonate Of lime(?)
on the surface as the water flowed from
the spring.
Third-Mr. Moore's expression, liken-
ing some of the volcanic vents ito bub-
bles on a bed of melted pitch or tar, or
those on a boiling mass of mud and
water hardly seems a happy one
Such description implies a homogeneous
mass of country like the basalt flows OF
Idaho and Oregon, or the rhyolites OF
Yellowstone Park, with insignificant
local craters or assures with extensions
OF the same general character. Here we
have:
Myers Mountain, a great basaltic
neck. The iron stained effect of SOL
fatarism Immediately north OF it is
probably due to contact of the ascending
waters with this basic rock. This ba-
saltic Gaping has protected the soft
tufts forming part of the mountain.
Columbia Mountain is probably up
lifted on its south end by an alaskite
laccolith, which is nicely exposed in the
Columbia Mountain Mining Company's
tunnel. The north end of the mountain
is the remains OF a rhyolite neck and
flow. The laccolith in the tunnel is seen
rising under a body OF more or less sill
icitied lime, which also outcrops in great
mass on the hill over and south OF the
tunnel. The tunnel is an interesting
feature of Goldfield mining. 1t is cross
cutting the alaskite, in this case a deep
seated plutonic rock. Elsewhere, veins
that have Deer followed down through
everything eruptives into the granite,
have then sometimes proven more uni
form in size and value. In fact, the
homogeneous character OF granite and
alaskite is micaless granite usually
makes a clean cut assure. .Alaskite
probably underlies a large area of the
Goldield camp, and something may be
expected of the veins entering it. The
supposition that the Jumbo tissnring