Tonopah bonanza. [volume] (Butler City [i.e. Butler], Nev.) 1901-1909, 1903-12-26
ORE DEPOSITS OF TONOPAH, NEW.
preliminary REPORT)
j. L.
Brief Review of the Salient Economic Features
Embodied i'm the Report.
d.
BY d. c. RALsToN, MINING ENGINEER.

the veins the report adds that so fan
as the veins are concerned they are
usually strong, straight and vel
defined, yet are not assure veins.
Examination shows that they are
rather replacement veins-replacing
the andesite in which they occur.
They seem to have originated along
zones OF fracturing. These zones oil
maximum fracturing, varying in
width up to six feet, became the
channels of circulat ton for the miner
alizing waters. 1t is pointed out
that by virtue of the process Of al
iteration the veins sometimes carry
their ores on the hanging, sometimes
on the foot, frequently in the center
of, and sometimes filing the whole
vein with quartz and ore. The full,
completed vein typities the last and
final stage of replacement by siiciti-
cation. The ore bodies are generally
of tabular form, and resolve them
selves, in some instances, into shoots
which manifest general rake to the
east.
Stephanite is the primary sulphide
ore OF these veins-the gangue gen
orally quartz; sometimes quartz and
orthoclase. This rich black anti
monial sulphide of silver commonly
carries some copper. This fact, it
may be added, is often regarded as
an excellent earmark of profound
permanency.
Argentite and ruby silver occur in
minor quantities, as compared to the
stephanite or its oxidized products.
These ores occur rather as second
airy and tend to enrich the Sulphide
of which they are the resultant of
alteration.
Passing finally to the oxidized ores
Mr.. Spur points out the fact that
nearly all of the ore in the famous
Mizpah down to its lowest depths is
oxidized, while the ores in the Mont
ana Tonopah are only slightly oxi-
died. Although in the Mizpah the
main shoots are regarded as prim
airy, since, as he says, evidence has
been found that coincide with the
original ones and have been oxidized
nearly in place; and, he concludes,
therefore it is improbable that the
transfer of material during oxidation,
bringing about loca concentration or
impoverishment has been great.
A noteworthy feature is empha-
sized respecting slight transference
and redeposition OF the precious
metals along the fault planes which
are later than the veins. AS previ-
ously pointed out in connection with
the drag" ores, such superficial
dispositions would only add to the
mask which some fault planes would
assume in Stimulating true veins.
In the application Of geological
principles, the report concludes, the
highest Importance attaches to the
determination of the position OF the
early anoesite. 1.-THE actual area
where the early andesite is very
Limited and in other portions of the
district it is covered by later rocks
land is cut through and displaced
"by them"
"Of the different rocks which cap
"the early andesite and the included
"veins, the oldest, the later andesite,
is regarded as the most favorable
''for prospecting: and in the light OF
present knowledge, a belt OF this
rock lying east and west of the
'Mizpah bill is probably especially |
favorably." Nor is it proved that
the Mizpah is the center of the min
eralized belt. 1t is suggested that
eventually it may be proved that the
strongest portion of this belt lies
north or south of the present locality.
At the same time it is to be borne in
mind that the trend OF mineralizatio
S east and west.
In the final summing up it is sug-
,ested that the later andesite is
worthy OF cautious prospecting. Lo-
'alities wherein the later andesite is
ntruded by rbyolite ought to be
Ivoided. The undisturded andesites
IRE inviting. Shafts sunk in dyke
IF neck are apt to continue indefn-
tely in such rock. Faulted regions
'lso are to be avoided. So also the
acites and rhyolites of the later in
rusions, and the brecciated rhyolite
hould preferably be avoided.
at is beyond question, therefore,
that the veins thus far found are
only q fraction of those which exist
in the vicinity"
The report will prove invaluable to
he miners, prospectors and opera
ors, and is timely. 1t reflects much
redit upon Mr.. Spur for his pains
,king efforts and his concise, definite
nd applicable conclusions and rec
Especial gratitude