The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1907-08-31
ROUND MOUNTAIN SUNNYSIDE
EDITORIAL Correspondence American Aiiss Rsvisw)

At the invitation of j. r. Davis, I ex-
the Sunnyside mine at Round
Nevada. on August 8. This
IL a very interesting property. operated
by the Round Mountain Mining comrsny
which is practically a close corporation
controlled by Messrs. LOTUS and Davis
of Goldneld. Harold Baxter is consult
ing engineer and James Mcdonald is SUI
perintendent.
The probable gold bearing area Of
Mountain is fairly extensive and
IL may be said with much confidence that
the district will become an important
one for its gold production. There is
now enough development to make II
clear that mining and milling can be
done economically and that large ore
bodies. besides those already opened.
may be reasonably expected. At the
same time. the vein formation is very
curious n would be more than pug
zling were II not that Developments in
the Sunnyside mine have shown how the
ore bodies occur. A careful study of
these workings should save much waste
in time and money 10 other companies
operating in the district. For that rea-
son. and because similar conditions may
occur in other belts Of the Great Basin.
l shall go rather particularly into detail.
The productive mines and promising
prospects of Round Mountain are in a
rhyolite belt which extends slightly
north Of east for about two miles. This
Is in contact with granite. as shown on
the Fairview property. Traversing the
rhyolite are dykes of porphyry and
dacite. The porphyry is barren. or
nearly so. and the dacite. exposed at a
depth Of 275 feet in Fairview ground.
carries iron sulphides and low grade
gold ore. This is the only sulphide yet
found in tho district.
The main assures are rather fiat and
are in rhyolite Except when they cut
across the porphyry dykes above men
tioned) and strike east-west. There is
a system of cross-fssuring. whereby in
Vulnerable veiniets. generally parallel
and nearly vertical. with northwest
strike, extend from the surface through
the fatter and larger veins. These VEIN
let's are. in places. extremely rich and
are undoubtedly the source Of Round
Mountain placer gold and are also re-
sponsible for much Of the enrichment of
the larger veins.
The ~Sunnyside vein has been traced
and opened by numerous shafts through
the three claims and fraction owned by
the Round Mountain Mining company, a
distance of 1000 feet. easterly through
the Combination, Antelope. Daisy and
Fairview and westerly through the
Great Western and Sphinx. The strike
is east-west and the dip about 80 de-
grees north into the mountain.
The peculiar feature of this vein. as
shown in the Sunnyside workings. is
that while for considerable distances
the hanging wall is unusually true and
we'll defined for this region, the foot
wall country. subjected to greater
stress, is remarkably folded and buckled
across the strike, forming a series OF
trough-like chambers with the dip OF
the vein. So far as the mine is opened,
$50 feet on the dip. the t%roughs. as !
shall call them. extend downward from
level to level, each maintaining its size
with fair regularity. The troughs vary
in size from a few feet across to large
chambers containing important ore
bodies. Between the troughs, the FOOT
wall quite closely approaches the hang
ing wall and at these points the ore Is
low grade. The wider spaces seem tc
have afforded the favorable channels fol-
ore making solutions in this case. Each
trough contains an ore body.
The ore shoot is cut off by a porphyry
dyke which is not only barren but has
broken the formation considerably. This
dyke has been reached in three levels
and marks the eastern limit of present
development in the mine. 1t is probable
that the ore shoot will be found beyond
this dyke. The placer ground below 1t
is barren, while beyond it is richer than
below the present Sunnyside workings
In parts of the mine the hanging wall is
regular n in other parts it has been
thrown out of its normal course.
Several large horses have been found
with ore on both sides and 1T is probable
that some of the Irregularities are due
to horses not yet recognized as such.
1t will be evident to every mining
man, from this brief description, that
the Sunnyside vein was a most difficult
one to develop. Much credit is due to
Mr.. Mcdonald for the tenacity with
which ne followed MS ore WHcIcNci ~
went. A drift run southeast in ore,
would after a few feet come to an ap-
parent fault. country rock appearing In
the face and with ore often obscured by
a slip IN the north side of the drift. This
fact discovered, a crosscut run northeast
would soon run into country rock again
the hanging wall. but then u~nrecogniz-
able as such. The puzzle was gradually
unfolded by persistent development in
ore. Three shafts ave been sunk and
several levels run out from each, with
raises and some crosscuts. The vagaries
of this vein are now so well understood
by the management that development
can proceed with confidence.
Sunnyside ore is brecciated rhyolite,
with some quartz and many tale seams
spreading in all directions. The gold Is
associated with iron oxides. The tale Is
often very rich as is the quartz ore
The vertical veinlets. which cross the
main vein with strike north so degrees
west, are from a knife-blade to four