The morning news. [volume] (Savannah, Ga.) 1887-1900, 1898-11-26
GOLD AsSAYING.
Details of the Work by (Which Mine
values Are Determined.
From Chambers Journal.

Values Are Determined.
From Chambers Journal
Imagine a gold mine. You may select
many chmates-Siberia or Africa, Klon-
dixie or Australia, California or India. Sit
uate your mine where you win; so long as
1t be a gold mine the procedure of assay
ing is the same ali the wide world over
Select a mass of ore, weighing, perhaps,
fifty pounds and smash it up. Do not eX-
pect TO see any gold in it, because the pre-
c.ous metal is probably SO thinly and uni
formly scattered through the quartz thai
il is impossible to spot grain together.
Continue grinding the ore till it is in the
form of powder. This powder is heaped
into cone, which is divided into four parts
of which the sampler takes two whose an
giles are opposite to one another. Mix these
Two parts thoroughly, and again divide into
| four; take two portions again, and so on
i'm a sample of convenient bulk is oD-
tanned. BY this logical method the sample
J yielded is, on any ordinary calculation OF
| proba biMty, certain to represent accurate
| ly the original mass taken.
A certain quantity of this sample is now
weighed out, two equal amounts being tax
| ing may be done in denOmina tional values
| of either gramnes or assay tons. The as
| say ton is a most convenient invention, aud
| is very simply explained. The ordinary ton
| contains 81, $685. ounces; if, then. we make
| a unit tan assay tom weighing &.665I
! gramnes, each Col of a gramme will equal
ole ounce per ton. Thus, no Calculation is
needed 1t all 10 estimate the gold rchEess
| Of an ore per ton.
/ serh ant GRnHTATp
| portions of the ore of one assay ton GA.
| IT. each With each mix thoroughly BIZ
| carbonate of soda, ltharge, boraX, glass
and flour in varying proportions; When
| thoroughly uniform in color empty the
mixtures in fire clay crucibes, and strew
| on the top a thin layer of salt. Put on
| the lids of the two crucib.es and surround
! them with living coal, coke or burning va
porized benzolne in a crucible furnace
! The crucibles are heated till the masses OF
ore and f1uxes are in a state of tranquil
| fusion-that is not bubbling or boiling
The white-hot fluid is then poured into
iron nolds and allowed to cool. On exam
nation, after cooling, the fused masses
! will be found to consist of: % A layer
of white substance, which Isl sat ~ A
| Stag. This is usually dark in color, often
resembling malachite, and is formed by
the fusion of the borax and soda with
the worthless or earthly matter (gangue)
| in the ore 90 lead button, produced
| from the litharge, or lead oxide, original
| w mixed in the charge. This lead button
contains all the silver and gold in the ore.
The heat of the furnace drives off from
the lead oxide its oxygen, so that pure
lead is If this, in virtue of its weight.
percolates downward through the Stag
during the heating in the furnace, and
eventually forms button weighing, if a
proper amount of flour has been added or
iginally about sixteen to twenty grammes.
The flour mas the effect of varying the
size of lead button produced, and is said
10 possess a reducing action.
The next step in the process is to get
rid of the lead without also losing the
gold and silver This is done by an opera
ton known as cupellation. The cupel is a
small round, bone-ash cup, which is
placed in a sort of fireclay tunnel with
one end closed up, known as a muffle.
The muffie is heated from the outside,
either by burying it with Goals or by
playing burning gas ON every part of it.
When the cupel has attained the heat OF
the interior of the muffie, the lead button
is placed in il and the door of the muffle
shut, so as to procure the greatest amount
of heat possible When the lead is seen
to be- melted and Tuning. the mufie door
is opened to admit the air, which is suck
ed in by the intense heat.
The oxygen contained in the air oxy-
dies the lead into lead oxide, and the
bone-ash cupel absorbs lead oxide like a
sponge but refuses to absorb the gold
and silver; so that at length there is left
in the cupel only button of the two pre-
cious metals. 1t is to be supposed that
two ore samples have been treated SINH
larly both in the crucibes and cupels
but for the sake of convenience, 1t is bet
ter to explain the treatment of one only
l 4 Ill.
weighs let us say, 00l6 of a gramme This
is noted down. The bead after weighing
is fiattened out in fiatting mill, so as
to expose as large a surface as possible
TO the nitric acid which is then added
to it, On heating the silver is dissolved
but, of course, the gold is untouched by
the action of any single acid. The re.
naming pure gold is treated with stronger
acid. called parting acid" to drive of
any suspected trace of silver, and ther
washed with water.
If the parting" of the gold from the
silver has been successful, the gold is lef
as a thin, small sheet. From this al
moisture is driven off by heat. On weigh
ing the gold may be as heavy as OOO7 OF
a gramme. Then. as II has previously
been noted that the total gold and silver
bead had weighed .OO16 Of a gramme. tn,
weight Of silver present must have beer
OOO9 of a gramme. That is to say. in on.
assay ton Of 32.6667 grammes there art
.OOO7 gramme of gold and .OO09 gramme o.
silver It has been stated at tn,
commencement of this article tha
in an assay ton each .091 o
a gramme represents in rea
ton one ounce. Therefore we hay.
seven-tenths of an ounce of gold-that Is
IA pennywelghts 90 dwt ozD-ant
nlne-tenths of an ounce Of silver-that is
IS pennyweights, to the TOM Quod era
faciendum.
Many minor processes, such as roast
ing. scoriication and inquartation entel
, into the work done in assay; but /
, has been desirable 10 make the process al
| ,.onr and free from cOmDllca lion ~ No.