Gilpin observer., 1905-06-15
NEWS FROM THE MINES and MILLS
Conditions at Tonopah.

Following is summary of J. E.
Spurs forthcoming bulletin on the
Tonopah gold discoveries in Nevada:
The Tonopah veins are similar in
nature, composition and origin to those
found in some of the richest mining
districts, such as the Comstock OF
Nevada and the Pachuca district Of
Mexico. Indeed, it is probable that
all Of these districts and many others
lie within single Photographic and
metallorgraphic province characterized
by similar veins formed at similar
periods. In the Tonopah district the
rich ores occur in the veins in the
shape of irregular shoots or masses
richness to the famous bonanzas OF
the districts mentioned. The geo.
graphical conditions also indicate that
such bonanzas were formed down to
considerable depths. These are the
striking advantages of the district.
which have justified considerable ex-
penditure of money in exploration.
The disadvantage of cost of pro-
duction is common to all mines In the
desert region, and If this were the
only drawback the production of the
district might reasonably be expected
to become enormous. A greater disad-
vantage, however, as previously
pointed out, consists in the disturb
ances which the veins have been sub
jected to since their formation. These
disturbances consist of both repeated
and copious intrusions of later vol
canic rocks and of faulting which &C.
companies the intrusions, forming a
condition illustrated in the ideal cross
section published last year.
By these disturbances the veins
have been broken in detail and some
times even displaced to such an ex-
tent that search for their continua-
ton is practically hopeless. In min
ing the expense of following a vein
Is increased by slight disturbances,
and where the vein is greatly dis
placed large amount of money must
be spent in exploration. however in
telligently this may be directed. When
veins belonging to one of the later
periods, especially that following the
Tonopab rhyolite-dacite intrusion. are
encountered it may be difficult for the
mining man to identify their character
or class. and much expense is incurred
in drifting along these in search of ore
usually not sufficient to pay for the
whole work done.
Moreover, the exploratory shafts
which have been sunk. particularly
during the last year. in the region
around the productive area indicate
that the earlier andesite, with its pro-
ductive veins, if, indeed, it can be
found in any large amount in these
regions, lies under an average of great
thickness of the subsequent barren
formations. Where these veins are
very close to the surface, as in the
chief productive area, the difficulties
of mining. as pointed out. are still SO
great as to make large profits often
matter of considerable doubt. and
whether similar mining and explora-
tion must be carried on at an increas-
ingly greater depth 1t becomes more
and more doubtful whether the results
will warrant the necessary outlay.
For these reasons, in considering
the balance struck between the highly
advantageous character of the ore and
the origin and nature of the veins
and the disadvantageous circum-
stances introduced by late disturb
ances, it impresses the writer that the
balance is at present rather on the
disadyantageous side.