Omaha daily bee., 1905-10-01
PART The ASSAYER PLAYS
How Values Of Ores Are Determined by
Scientific Experts
SEPARATING PREclousMtTALS FROM BASE
Method of sampIinE Ore and Then
ReducinE the sample to an Exact
Figure of value by the
Fire Test.

Do you know anything about the work
Of the assayer? Does it seem mysterious
to you that a man can take the most COM
pick piece Of ore that you can bring him
and in a short time tell you just how much
lead, silver, copper or gold IL may contain3
Not only this he will be Just as accurate
as to the baser constituents-the lime, the
silica, the barium. He can tell you whether
it is an oxide a sulphide or a carbonate
II he has had long experience he can tell
you very near the locality from which the
ore came.
After he has told you what you have IN
the ore, he can also tell you the best way
to get 1t out. and this may mean a great
saving to you. When all these things are
known you can operate your mine with
economy
The assayer looks at your piece of rock
and he may ask you II this is a fair sam
pie Of what you have in your ledge Of ore.
Perhaps you say you don't know. Then,
II you will be advised, you will go back
to your mine and go over the whole of
the exposed surface OF your outcroppings,
or the face Of your drifts, or tunnels, or
shafts. as the case may be, and by gather
ing a large number of pieces taken indis-
criminately you will get fair sample.
what the Assayer Does.
The assayer will look at these pieces.
II they look weather-be beaten, or of a red
rust color from iron, he probably will de-
eide that the samples are oxide. II the
samples are black or show bronze yellow
crystals. or give up white fumes on heat
ing, he will say they are sulphide Then
he will crush the ore to finest powder and
mix with 1t what he calls fluxes. such as
soda, lime silica, as the case may re-
quire. These, with the ore, cause it to
melt much more easily.
Now, the most important thing he puts
In, If he is testing for gold, is something
that will gather Up the minute particles Of
gold or silver and bring them together.
This, the assayer has discovered TO be
ltharge, one of the oxides of lead. This
acts in melted ore much as the eggs a
housekeeper uses with which she settles her
coffee. He puts with the litharge some
form Of carbon, flour, argol and charcoal
This reduces litharge to metallic lead, and
| in this state II acts as the net, so TO speak,
| that gathers the precious gold. II the ore
| is a sulphide, there need not be so much
charcoal or flour, or argol used; and there
| lies one difference in the two classes of ore.
| When he has made this mixture to his
| satisfaction, he puts 1t in a crucible and
covers it with salt and sometimes with
pOIdA- his SAT- Keeps IluI6 even Ntlll-
perature in the charge and prevents spat-
| tering. He beats the mixture he has made
to high temperature, in a gasoline muffie-
furnace. or coke-stove. for twenty minutes.
| The melted ore is poured out and cooled
and the lead, with its gold and silver is
| found settled to the bottom, in what Is
| allied a button.
| The next operation is to separate the lead
| from the gold and silver. The button is put
in a cupel, a little cup made out Of bone
ashes. Now put this in the furnace and
you will see the cupel getting yellow while
the lead disappears The heat, with air.
makes the lead into an oxide again, and
the bone-ash absorbs it as fast as It is
formed. Not so with the gold and silver.
They will be left in a little globule, after
the lead is all gone.
Separating Gold from silver.
Now the assayer must be careful, for this
little globule is easy to lose. But with long
experience, he picks 1t up and puts 1t In a
little vessel called a casserole To sepa-
rate the gold from the silver the casserole
Is filled with pure nitric acid. This will
dissolve silver but not gold. When tn,
silver is dissolved the gold is collected and
weighed II you have weighed the little
globule before you put it into the acid, a,
you should have done, you take the weigh
of gold from the weight of the globule anc
the difference will be the weight of tn,
silver.
Now you know the weight of gold ant
silver, and you should know how much or,
IT took to yield what you have got. DID
you weigh your ore when you had /
crushed? The assayer does. Then he car
figure in this wise: If half pound of or
gave me / cent in gold, and / half-cen
in silver; a ton of ore, which is the usua
weight of ore considered, will give me "a
in gold and 500 in silver
This is the great question that the mine
wants answered, and. telling II roughly
the assayer goes about 1t as herein de
scribed.