Corvallis gazette. [volume] (Corvallis, Benton County, Or.) 1900-1909, 1900-07-27
ACCURATE .SAMPLING
Considered Essential to Ac.
curate Assaying.
PRACTICAL MINERS VIEWS

Protests gainst the Use of Assay Ger.
tificates as Documentary
Evidence. .+z g13.s.
Accurate sampling is quite as essen
tial as accurate assaying, for if the
sample does not truly represent the lot,
or mass, from which it was taken, the
subsequent assays will be valueless.
The assayer OF chemist will usually re-
ceive the samples already prepared,
but as he will occasionally be called
upon to take his own sample knowl.
edge of the art of sampling is essen
tial."
In the Northwest q majority of the
samples brought to an assayer are
taken by the prospector, or other inter-
,ested party, and as the assay certifi-
Gates are often used as the document
ary evidence of the value Of the profAx-
ty, the assayer should be very careful
to state ON the face of such certificates
exactly from whence he obtained the
sample on which the assay was made.
If an assayer samples the ore him
self, he owes it to his client SO to state,
as it doubles the value of the certii-
cate. If he did not take the sample
himself he should place the RESPONSE
bility of the sample where it belongs,
by stating who did take it. Without
some one known vouching for the ore
of the sample, assay certificates should
carry no weight as documents. This
oo, Lo,% ba nlichal bu bo @.
sayer seeing to it that his printed GER
tificate blank is worded to cover the de.
sired points, telling the whole story
and protecting him from any after talk.
/ must protest. also. against the
habit of certain assayers in filling in
the value of the ore on the assay certifi-
cate, as they do, at the price of the
metal in marketable shape delivered in
New York. 1t shows a gross ignor-
ance on the part of the assayer as to
the value of the ore here, and often
misleads the prospector frightiully, at
the same tine furthering and opening
the door for fraudulent practice. I
have seen, this summer, assay certifi-
Gates upon which the copper of 5 per
cent ore was figured out at 18 cents.
equal to $18 per ton, whereas no smelt-
er could afford to pay more than about
one-third that price.
A good practical rule to use in fgur-
ing out approximate values of sui
phide ore, at present market quota
tions, is as follows:
Allow $1.25 for every per cent of
copper the ore contains.
Allow 40 cents for every per cent of
lead the ore contains.
Allow SO cents for every ounce of
silver the ore contains.
Allow $40 for every ounce of gold
the ore conatins.
These values are for ore delivered on
the line of railway.
The prospector has to sample his
own claim and wishes to know the
truth. Naturally, / ask how he is to
do it, and the following remarks are
for his benefit, not for the professional:
In sampling lead, if the vein is SO
that it will all have to go for treat
ment, section of uniform thickness
right across the whole face of the lead
should be taken for ore samples.
Another, and quite as satisfactory a
method, is to sample all the rock that
comes out of the prospect, or sample
the dump, If there is any, by cutting
channels through it on the same princi-
pie as in sampling ledge.
1t must always be borne in mind in
sampling that there is liable to be
great difference between the dump and
the fine ore, and consequently due re-
gard must be had to getting the proper
proportion of each.
Hand-picked samples are never reli-
able, and should always be avoided.
Experienced mining men frequently
take hand samples of particular classes
of the ore in a mine, have these assayed
and often from these results they esti-
mate what grade of ore they are min
ing. This may be correctly done, and
it is wonderful how close to correct
assays experienced men can guess"
but it is uncertain at the best, and
dangerous for inexperienced persons to
attempt to be guided by such estim-
mates.
Assays cannot be averaged, unless
one knows the actual weight of the n,a-
terial represented by each assay, and
only then by long calculation, too
long to describe here. except briefly.
In nine cases out of ten when the
average assay of mine" is spoken of,
it is incorrect and is usually obtained
by adding up number of separate as
says and dividing the sum by the num-
bers of such assays. It quite correct
to take an average sample, have that
assayed, and call it the average assay;
but this is seldom done. The correct
average assay may be obtained by null
tiplying the weight OF each lot of the
ore by the assay of such lot. and the
product of such multiplication and
divide this sum by the sum of the
weights of the various lots of the ore.
The quotient of such division will be
"the only correct average assay" obtain
able. O. M. ROSENDALE,
In Portland Telegram.
Castle CraE Tavern Burned.
Dunsmuir, CAL, July 23.-Castle
Crag Tavern, fashionable summer
resort in the Sierra mountains, was
destroyed by fire, together with its
contents at an early hour this morn.