Tonopah bonanza. [volume] (Butler City [i.e. Butler], Nev.) 1901-1909, 1904-12-31
Y. 5. SURVEY,
j. Il. Spur Tells of Formations
of GOldfieId District.

OF Gold1ield District.
The new camp Of GoIddelds, Ne,
vada, was revisited in November Of
this year by j, E. Spur. Of the
United States Geological Survey.
This district lies about twenty three
and one-half miles south of Tonopah
and was located late in the spring OF
1903 Shortly after the discovery Of
gold IN this district it was visited by
Mr., Spur. A little work was then
IN progress on what is now known as
Columbia Mountain, but up to that
time no good strikes had been made.
In January and February, 1904, how
ever, rich finds were made in certain
spots south of Columbia Mountain.
The district has now an approximate
population of 5000. The town of
Goldtields has sprung up, and a mum
Der oil smaller adjacent camps have
been established. 1t is estimated
that up to the present time about
two million dollars worth of ore has
been shipped from the district. Most
Of these shipments have been made
IN the last five months.
The district is bounded on the west
IN part by % la~va-capped mesa, the
erosion Of which of which has laid
bare the underlying gold bearing
rocks. The auriferous region is
characterized by numerous low. ir-
regular ridges standing out from the
lower and ore nearly level surface.
These ridges owe their origin to hard
reefs of quartz which form their
crests. Their resistance to ero,
sion has left them %protruding thus
above the general elevation, and in
these quartz reefs the a%uriferous de-
posits are found.
Columbia Mountain is the most
prominent Of these ridges, and some
notes on its geology were made pub
lie by Mr.. Spur, last year, in bul
letin 225, published by the United
States geological survey. Near the
south end Of the ridge the rock is
largely alaskite IAN igneous rock con.
sistiug of quartz and feldspar), which
Is sometimes OF granite structure,
and sometimes very dne-grained,
ever resembling quartzite. White
mica or %muscovite is sometimes pres
ent, and pure quartz veins or bikes,
of similar origin, also occur. On the
north end of the mountain the rock is
a very much altered highly silicifed
rhyolite; in this rhyoIite are broad
masses Of white to purplish aud red
dish cherry quartz, which extend IT,.
regularly in a %northerly direction.
The saIicified areas have i'll. defined
walls, aud the highly %mineralized por.
tons which they enclose are very IT.
regular.
On his last visit Mr.. Spur took
notes over Am extended area, and
made interesting additions to his
knowledge Of the geology Of the dis
trict. The area Of the known bodies
has spread since last year SO far be
yond Columbia Mountain that values
are now found over an area about six
mites square. The most productive
area measures two to two and one.
hall miles in either direction, The
chief mines at the present time are
the Jumbo, the Combination, the Jan.
uary and the Florence, all grouped
together about "a mile south of the
southeast end Of Columbia Mountain.
Some five miles northeast of Colum.
bta Mountain is the Diamondfe,d
group, including the Vernal. the
Quartzite aud Black Butte, from
which shipments have also beer
made. Other ore deposits have been
developed in various parts OF the
field,
The rock in that part of the field
visited by Mr.. Spur on his last trip
tthe region of Columbia Mountain,
Diamondfield and the Jumbo group of
mines) was found to be almost en-
ttrely volcanic, consisting of rbyol
ties, rhyolite tufts, andesites and
basalts, all probably Of Tertiary age.
One andesite examined microscopic.
from near Tonopah club is a
hornbIende andesite, resembling the
early andesite at Touopah; a patch of
basalt from near the Florence is an
augite basalt, like that Of Siebert
mountain at Tonopah. The rbyolite
resembles that Of the Gold mountain
district, which lies about four miles
south of Tonopah, on the road be
tween Tonopah and Golddeld; and
this Gold mountain ~rhyolite, again
resembles closely some Of the phases
Of the earlier (dacitic) rhyolite at Ton
opah. The relatives age of the rock
at Goldtield has not been determined
but it probably corresponds to that
similar rocks at Tonopah.