The star. (Reynoldsville, Pa.) 1892-1946, 1896-01-08
TESTING ORES.
How Assayers Discover the Value
of Minerals.
The Process of Sampling Used at
the Mines.


stranger who wanders up and down in
the labyrinth Of shafts and tunnels,
diggings and dumps Of genuine
mining camp, perhaps there is no sub
! ject more full of interest than the pro-
cess by which lump of brown ore,
which, to his inexperienced eye, looks
not In the least attractive, is made to
yield its share of silver and gold; or
the means and methods by which the
mining man at his side so confidently
assures him that ton of that ore will
go 1913 ounces in silver and S17 SO in
gold.
Even the Eastern mining expert,
or graduate from some mining school,
will wonder how, in the log cabin or
pine shanty, destitute of all the
elaborate paraphernalia to which he
has been accustomed, these results
are so readily and accurately OBJ
tanned.
AS general rule the majority Of
the ores, except those containing the
precious metals, for purposes of pur-
chase and sale, are valued according
to the cost of mining and shipping,
so that, except for metallurgical pur.
poses, it is unnecessary to seek to de-
termine with much accuracy the con-
tents and value of such ores.
In the case OF ores rich in the pre-
cious metals, however, it is entirely
different, as in their purchase and sale,
both parties, the buyer as well as the
seller, want to ascertain accurately
and to a certainty the value of the en-
, tire lot. Tho methods by which this
knowledge is obtained are so simple
as to be easily understood and prac-
tised by many man who does not
know the technical symbols of the
metals he is determining, or could not
give scientific exposition of the
process; but, nevertheless, in his line,
he is an accurate and successful as
sayer.
When q quantity of ore is to be
sampled for assaying it is first broken
up by an ordinary rock crusher into
pieces the size of an English walnut,
after which it is shoveled back into the
car, but in such a manner that every
fifth shovelful is thrown aside by it.
self, the remaining four-fifths being
finally taken away. This fifth portion,
known as the ''sample," is then re-
duced to much greater degree OF
fineness by means Of Cornish rolls. 1t
is then piled on the floor in a cone,
hattened out, and divided into four
equal portions; and two opposite quar-
ters are then removed. The remain
ing quarters are again thoroughly
mixed, and again piled in cone, fiat
tened and quartered; this operation
being repeated until the sample is
reduced to 100 pounds. 1t is then
weighed repeatedly, for the purpose
Of determining the amount of mois-
ture contained in the ore, which in
some ores, especially those of the
concentrates, is so considerable as to
make very appreciable difference in
the weight. The moisture is then ex-
PEELED, and the ore is crushed to such
a degree OF fineness that it can be
passed through sieve containing 100
holes to the linear inch. The sample
is next put up in small glass bottles,
which are sealed with sealing wax, and
then stamped, for the purpose OF
preventing the possibility of their
being opened or tampered with with
out detection.
The above IS the process of sampling
used among the mines, and the sample
is now ready to be assayed, but only
a small portion of it will be used for
that purpose, and the quantity gener-
ally taken is what is known as an
"assay ton," which weighs 80, 166
milligrams, or little more than 45O
grains troy weight. This definite
amount is taken, partly as a matter of
convenience, and also because the
assayer wishes to ascertain, as quickly
as possible, how many ounces of the
precious metals to the ton are con-
tained in this ore. The method used
depends upon the following principle !:
The avoirdupois grams ton of 1000
pounds contains 20. 165 ounces troy
weight; hence when 20. 166 milligrams
of the unassayed ore are taken, the
weight of the resulting ''button" of