The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-06-12
The Valuations of Mines
BY T. A. Richard Delivered at Harvard
and California Unive Last April
Grade Versus Cost.


concerning the cost of handling 1t
Here the expert evolved per saltun
gets into trouble while the man who
has been mine manager is in his
element. To estimate the figure to bs
deducted from the yield in order t.
arrive at profit, 1t is necessary tc
know the costs Of stopping, timbering
milling, road making. erection of ma
chinery. general expenses. item by
item The other method is Just to
guess twice and divide by two for the
sake of accuracy. Many have blum
dered just In this way. In new
district most of the information OBJ
tainable will be furnished by pros
pectors. diggers and local promoters
most Of whom have no accurate know
ledge on these points; and when they
have it, they do not feel impelled to
donate It to the novice who happens
along.
If, then. you find yourself In such a
dilemma, what are you to do? If you
own to yourself that you don't know
what the cost of mining will be in this
new district, you are ahead of the man
who thinks he knows, when he does
not. For you admit void and are
anxious to, fill it. Having this saving
grace you are likely to anticipate my
advice: Go,to the best mining engineer
In the camp and ask him to tell you
q uhof t,o MI ho oyo
cost Of mining. If he is a true profess
sional man he will be glad to help you,
remembering the time when he him
self was in the same fix. Don't bluff
go frankly and ask him for the infor-
nation: and If you can get data from
several men, $50 much the better
Average Yield.
Thus at first hand or at second hand
you have ascertained the average cost
per ton of operations at given mine;
the next step isito find out what is the
average yield of ore; which is done by
taking representative fragments and
subjecting them to assay. This is
'sampling." The methods of sampling
vary. Twenty FIVE years ago it was
mine, sexamine the records and maps
and then take a turn underground.
where. they obtained one or two speci-
mems lof the ore and took few grab
samples On this slender and danger
Gus evidence they based an opinion on
the value of the mine. 1t seems abb
surd today. when sampling is almost
a fine art, and many of the younger
generation will be inclined to sheer
at the unsystematic methods of their
own, grandfathers. OF course, it was
wrong, and as much inferior to current
practice as rule of thumb is inferior to
technical science Many mistakes
weret made and mine valuation was
frequently mere guesswork. Never
the-less, some of the engineers of 80
and 40 years ago passed remarkably
correct judgment on mines upon the
basis sof apparently inadequate evil
dence.' 1t is also fair to say that some
of the moderns. with elaborate assay
plans, have made egregious errors of
inference.
Obviously, the right method and the
right man must be conjoined to yield
the best results. As matter of fact
the old method was not always as hap
hazard as it seemed For instance, a
man examining copper deposit, the
richness Of which was dependent on
the presence of chalcopyrite, and
KIN owing that mineral when pure con-
tanned 80 per cent Of copper could
gauge the approximate value of the
ore by the proportion of chalcopyrte
visible. An experienced man will
learn more about mine in an hours
visits than q novice in week The
old-thner notes where the slopes are:
from lthese Slopes he learns the lock
of the, good ore; then he can see for
himself where else in the mine similar
ore EXISTS; or he observes that a spe-
rific mineral marks the valuable part
of the, lode. and having noted this in
llicative mineral, he infers the rich
ness of the ore in the various work
ings: The goes to the bottom of the
mine land ascertains whether any
is manifest in depth; he walks
10 the ends of the levels and sees Tor
whether the ore bodies are
persistt mt in strike and he takes the
distribution of the slopes as signs of
ground. One or two sam
pies will check his deductions, and
while b is judgment will not be as safe
Is II he himself had caused the work
ngs to be m.9led thoroughly he is
still ahead of many young men whose
noils are sharper than their inte'li-
-ence. In course rf time the profess
sion learneil that Grab samples anu
casual infere noes we're risky. AM, thus
!,er samplinf, Of mines developed "n''
( became a.! labor,ous undertaking 'n-
,olving the expenditure Of much time
md money. AS one no longaT prac-
itioner. confess that what ~ wanted
$ a comb nation of the insight exh'o-
ted by the grandfathers and the sss-
EN- shovrn by their grandsons. 30"
an not value a ruine with moi,
.e eds brs ms also:, nor can YOU aP-
praise a mine by Inference only 20"