The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-12-03
FORMATION AND AGE OF
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trouble is that the expert witness is
not expected to give a clear. straight
forward story Of his view of the mat
ter. but is urged to put the loud pedal
on the points which favor his client,
and to muzZle those points which are
,disparaging to his clients interest,
Much of the expense and confusion re-
sulting from divergent expert opinion
would be avoided If the experts were
employed by the court and not by the
contestants. Their capacity then
would be to make the evidence clear to
the court and to explain the conditions
without bias or prejudice to either
side.
"The next subject l propose to con-
slider in this talk undertake with fear
and trembling, In fact, l would not
take 1t up at all If were not sure that
someone would ask about 1t anyway. 1t
is the question of increase of values in
veins with depth. 1t is. of course AN
Extremely important practical ques>
tion, prospector finds a vein digs
a shallow hole in 1t and gets an assay
Of S. gold to the ton. The practical
question which confronts him then is
whether or not he Is justified in sink
ing deeper hole with the hope OF
getting higher values. My hesitancy
In taking up this question is because
| It involves chemistry and some of my
hearers may not be familiar with
chemical reasoning, However, | shall
endeavor to present the main facts as
simply as possible.
"There are two things to be con-
idered in this problem. First, the
distribution of values in the vein as 1t
was originally formed; and second, the
changes which have affected the vein
since it was formed. We will dispose
of the first point briefly by stating
hat as a general rule, the metals or
iginally deposited in the vein were
rather evenly distributed and that no
increase in value should be expected
by sinking
THE second point involves the con-
sideration of the chemical changes
which go on near the surface in the
minerals of vein. Near the surface
some of the minerals In vein decay
and the metals go into solution and
leach out from the upper part of the
vein. leaving it poorer than 1t was
Originally. When such thing hap
pens the vein may become richer with
depth, at least down as far as the
phase of the teaching problem must be
considered where the metals leached
from above are redeposited in the vein
further down. Such redepositlon pro-
above where the metals have been
cached; second, middle zone richer
than normal, where the leached met
ais have been added to those original
ly in the VEIN and third, below these
other two zones the original vein I'M
disturbed by these teaching processes
"Now to come back to our CONNER
cial problem, the statement can be
made that the commercial ore in most
mines throughout the world comes
from the zones where these teaching
processes have been active. In Other
words, the richest ores are in the up.
per parts of veins and with depth the
veins get poorer often too poor to pay
for mining. Most veins in which pay
ore is found are commercial only with
: in 500 feet Of the surface, or, to STATE
1t in another way, most of the pay orr
is within 500 feet of the surface.
I IF you analyze this statement lit
tie further you will see that 1t imple
that most veins as originally formed
are too lean to pay to work. and tina
the pay ore is made by the teaching
processes which take place in it's up
: per part.
1 Leachinn of Metals.
Now if we attempt to apply thi
reasoning to particular metals; If W
: ask will copper leach? will gold leach
. will silver leach? will lead leach? wi
r zinc leach? we place ourselves at ono
j in the midst of chemical reasoning
We must consider the chemical ma
= ture of the original minerals in whc
= the metals are found, the chemica
d changes which these minerals may un
: dergo in the upper parts of the weir
: the solubility of the new product
- formed, etc. The economic geologis
! has done a lot of investigating alon
= these lines, but it must suffice for on
e purpose to give very briefly the re
e suits as born out by observed facts |
., the ground.
h 81. Copper does leach and redepos
further down.
20. Zinc does leach, but does ne
" usually redeposit.
v "3. Lead teaches with difficulty.
- "a. Silver sometimes teaches an
redeposits.
49, Gold seldom teaches.
! "To state this again in a practici
a way, we can say: Copper and cir
veins may become richer with dept
y silver veins sometimes do, lead ar
v gold veins rarely do.
II have already called attention