The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1910-10-01

Ne wNork firm of engineers known rs
the Constant Herz;g company, who was
here for some time making an exhaust
i've examination of the Jumbo Exten
sion estate, has submitted his report 10
ihe officials of the company. TIE re-
port shows that there is more than So.
100000 worth Of ore, gross. exposed in
the Vinegorone fraction of the estate
alone. and that this ore nav be mined
and milled at a profit of $2.363, 900.
The report covers under separate head
ings the various holdings of the com
outlines the various workings ard ore
bodies in detail. Nv. Herzig. rs con
s%ulting engineer for the Jumbo Exten-
SION company, also outlines working
plans for the mining of the property,
which, it is predicted, will sooE be
started. As to the geology of She
property, Mr.. Herzig says:
Geology.
- - " u iHtOiitiph W ulSCOoS INT
geology of Goldfeld at any consider
able length, because this question has
been treated Complementary in the
publication of the United States Geo
logical Survey previously mentioned.
Our discussion of this subject will deal
more particularly with the occurrence
Of the ore values and their general re-
iationship to the value of the property
as a whole.
The rock formation of GoldfelG is
principally dacite. lathe and andesite,
heing three members Of the lava series
If rocks. Speaking generally, all the
bodies opened up 10 date have heea
found in these three rocks, although
exploration is lacking to demonstrate
The existence or otherwise of pay orc il
The underlying formations. 1t is prob
able tlat the alaskite, a granite roll;
outrropping on the TANKS Of Columbia
Mountain, takes Q dip rpder the latte
and unlerlieS it throughout the entire
field. A number Of s:rong silicious
3utcrops are a prominent feature Of the
.andsclpe and indicate zones Of frac
turing and subsequent siliciieation Of
he lava rocks. These silicious zones,
i, arriving in width from . few feet -
hundred feet. were evidently
formed prior to and independently Of
.be ore bodies which were deposited
ls a later period. Investigation ind
that there a1e at least three dis
-inct characters Of orc in the Goldfetd
district, probably corresponding 70
.hree dist;nc. periods of naturalization.
So far IS known. the ore bodies are con-
ined entirely within the limits of these
,~ilicious zones and owe their origin to
! f~racturing Of tins silicious material.
because il was more brittle aad there
more susceptible 30 fraeturins
the porous and coarse rocks sur
tounding it. The ore bodies with
which we are concerned are u~rdoubsed-
a replacement Of the country rock
ilorg lines of weakness following frac-
planes aud to some extent open
il the rocks.
The vaiues throughout the camp are
extremely %errasic. Although the val
pes occur in fairly well defined shoots
the values within these shoots them
selves are extremely spotted, as parts
being worth thousands of dollars per
ton are surrounded by rock not assay
NO more than - or So per ron. \ con
Of affairs such as :his makes the
estimation of ore reserves IN exceed
inqlv difficult one. and requires q cor
side~able amount Of skill TO secure the
most economical results in the mining
operations. IN many places the ore
bodies are mined for a width OF from
% 10 40 feet. 4 careful sampling of
such exposures as were accessible to US
shows that in general shere are two
~well-defned high-grade streaks sepa
rate dbv comparatively low grade ore
this low grade portion, as a general
rule. being either ~unpayabie OF very
nearly 80. This question will again be
discussed unde the head of" Mining.
Very often the high-grade values are
continuous ii these foot aud hang
ing wall streaks, and .ofsen high values
may be found in the ground lying be-
tween them, SO that the entire width Is
pay ore.
our Investigation indicates that the
ore shoots have a definite pifeh and Dup
along the strike of the ore channel aud
nj the same time there are two series OF
rore a. less parallel fracture planes,
one Of these sets Of fracture planes fol
lows the ~sinuosities of the ore channel
and lies parallel % IT, while The see.
L lrnoIr .apoee the first sci bIln