Gilpin observer., 1904-10-06
How to Get True Assays.


chair of geology and mining in That
institution, contributes a valuable arti-
Gle to the Laramie Republican. The
professor graduated last June from the
Colorado School of Mines, but is suffi-
cienNy mature in years to insure sue
cess as teacher. In the article re-
ferred to the professor explains why
many samples submitted for assay fail
to give correct showing, regardless OF
the careful and conscientious efforts OF
the assayer to arrive at the true value
of the ore body from which they are
taken.
ION account of the very many poor
samples which are sent to assayers by
Wyoming people, as well as from older
mining states, l have thought it may
pay to tell why the samples are unre
liable and suggest cure" says the
article.
In the first place, many samples sent
in consist of single fragment of rock,
oftentimes no larger than a thimble.
Now, If one will but stop and think a
moment it will appear how ridiculous
it Is to expect to get any idea of the
value Of body of ore from a single
fragment of this kind. A vein is usually
very variable in the amount of value
that the various parts OF it carry. For
instance. there is often layer of clayey
substance on the wall that may or may
not carry value. Next to this there may
be streak of pure quartz. then per-
haps streak of mineral, then some
lime. and so on. Now, If a single frag
ment be chosen from any one of these
portions of the vein it is self-evident
that the other portions will not be rep
resented in the results from as assay OF
that fragment
Again, the upper part of vein is
usually oxidized, rotten. and any gold
in 1t will be in the native state; that is,
will be in small nuggets or particles OF
pure gold. Now, If single fragment
of this material be assayed it will either
assay too high on account of the pres
ence of nugget in the piece. or it will
run too low, because all the gold which
was at one time in it is now carried into
the adjoining rock.
Another common sample consists of
two or three pieces of entirely different
rocks. We recently received a package
containing three rocks. One was
pice of granite, fresh and clean, the
next was a piece of badly decomposed
granite, and the third was nearly pure
calcite Qime). These may have repre-
sented the two walls and the filing,
but it is not likely. The three rocks
were ground up together and assayed
and the results forwarded to the sender.
But what good will it do him? He sim
ply knows that one or two, or perhaps
all three, of the rocks carry value. but
he does not know which rock is worth
working on, or how much value it
carries.
Let us now turn our attention to
sample which will give true results.
Let us suppose that three-foot vein
has been opened and we wish to know
its value. Instead of picking up a
piece land 1t is human nature to pick
out the best looking piece) we will
get a sample which will represent the
full width of the vein. To do this
strip of rock. say six inches wide and
four inches deep. and reaching from
wall to wall, is taken off the bottom
of the hole This rock is now taken to
some clean. level place and broken TO
pieces the size of an egg, after thor
oughly mixing. a fourth is selected,
care being taken that a fourth of the
fine material. as well as the coarse ma
terial, is taken. and the rest thrown
away. This fourth is now crushed finer
and quartered again, until sample
small enough to send TO the assayer Is
obtained. This sample will contain
small particles from each part of the
vein, and each part of the vein is rep
resented in proportion to its width.
This is as it should be. IL you divide
the sample in two and send the two
halves to different assayers their re-
ports will check But IL you pick up
fragment of rock from prospect and
t.
pick up another fragment for Assayer
B, do not expect their assays to agree.
1t will be the merest chance il they do.
"And right here let me enter plea
for the assayer. He has to work with
what you send him. He cannot help
1t If you fail to secure proper samples
for him. His report will show the ex-
act value of the particular small par
eel of rock you sent him. If that par
Gel does not truly represent the ore,
he Is not to be blamed. The remark
is often heard: What is the good of
an assay, the ass2yers never agreeg
But you try sending them samples
which are the same and you will be
surprised how closely they Will agree.
1T Is sometimes intimated that the
assayer tampers with the true re-
suits No assayer who hopes to re-
main long In a community will do any
thing of the sort. His reputation for
reliability is his chief asset, and he
will not risk losing 1t. He has no
reason to falsify his reports, and he
will, in fact, use all means in his
power to make his reports accurate
and reliable.
''Of course. as in every profession,
there are quacks. Any man who can
build fire under an assay furnace
and can tell the difference between
iron pyrites and limestone, is permit
ted to open shop and hang out his
sign as assayer. But almost the same
can be said of a doctor or lawyer. and
a person must use some discretion. In
either case to find out whether he Is