Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1898-11-24
COLD ASSUMING.
Details of the Work by Which Mine
Values Are Determined.
(Chambers's JoarnaI)

(ChambeIsS JodIhai)
IMAGINE q gold mine. You may select
many ciirna tes-siberia or Africa, Klon-
dixie or Australia, California or lnola'
Situate your mine where you VIII; so ions
as Il be a gold mine the procedure o.
assaylng Is the same al the VIDE worH
over. Select mass Of ore Weighing, per
shaps, fifty pounds. and smash 1t up. DO
not expect 10 see any gold in It, because
The precious metal is probably so thiny
and uniformly scattered through the
quartz that it Is impossible 70 spot grain
together Continue grinding the ore Till
A. is IN the form Of powder. This powder
Is heapod into a cone. which IS diVlded
into four parts, Of which the sampler
takes two whose anglers are opposite to
one another Mix these two parts tho
roughly, and again divide into four; take
two portions again, and so on TIL sam
pie OF convenient bulk is obtained. NY
this logical method the sample yielded
IS on any ordinary calculation of proba-
bility. certain 10 represent accurately the
original mass taken.
A certain quantity Of this sample Is
now weighed out. two equal amounts De-
ing taken as checks upon each other The
weighing may be done in UNCONVENTIONAL
values Of either grammes or assay tons.
The assay ton is most convenient in
venton. and is very simply explained.
The ordinary ton contains S2,6666 ounces;
II. then, we make a unit IAN assay tom
weighing S2GG57 grammes, each .00i of a
gramme will equal one ounce per ton.
Thus, no calculation Is needed at all TO
estimate the gold richness Of an ore per
ton.
Say we weigh out, then two separate
portions OF the ore of one assay ton ca.
To each. With each mix thoroughly BIZ
carbonate of soda, litharge, boraX, glass,
and -four in varying proportions; when
thoroughly uniform in color, empty the
mixtures in fireclay crucibles, and strew
on the top q thin layer of salt. Put on
the lids of the two crucibles and sur
round them with living coal, coke, or
burning vaporized benzoline in a crucible
furnace. The cruclbles are heated till
the masses Of ore and fiuXes are in state
OF tranquil fusion-that is, not bubbling
or boiling. The white-hot fluid is then
poured into iron moulds and allowed TO
cool. on examination, after cooling, the
fused masses will be found to consist Of:
% A layer of white substance, which is
salt. (2) 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
tgangue) in the ore. 90 A lead button,
produced from the litharge, or lead oxide,
originally mixed in the charge. This lead
button contains all the silver and gold in
the ore The heat Of the furnace drives
OF from the lead oxide its oxygen, so that
pure lead is left: this. in virtue Of its
weight, percolates downward through the
Stag during the heating in the furnace,
collecting all the gold and silver present,
ana eventually forms a button weighing,
IL proper amount Of flour has been
added originally, about sixteen to twenty
grammes The flour has 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
Hon known as cupellation. The cupel is
A small. round bone-ash cup. which is
placed in sort of flreclay tunnel with
one end closed up known as a muffie
The muffle Is heated from the outside.
either by burying 1t with Goals or by play
ing burning gas on every part of 1t. When
the cupel has attained the heat of the
Interior of the mufIie, the lead button Is
placed IN II. and the door OF the muffie
shut, SO as to procure the greatest
amount of heat possible. When the lead
is seen to be melted and Tuning, the
niuffie door is opened 10 admit the air,
which IL sucked in by the intense heat.
The oxygen contained In the air oxy-
dies the lead eto lead oxide and
the bone-ash cupel absorbs lead oxide
ike a sponge, but refuses to absorb the
gold and silver. so that at length there
. left In the cupel only q button of the.
two precious metals. II is to be sup
posed that two ore samples have been
been treated similarly, both In the cruel
sles and cupels; but for the sake OF con-
yenience IL is better to explain the treat
nent OF one only. The bead or gold
Ind silver obtained weighs. let us say,
00i6 OF gramme. This Is noted down.
rhs bead after weighing Is fiattened out
IN a nettipg-mill. so as to expose as. large
\ surface as possible TO the nitric acid.
which Is then added to IT, On heating. the
,ilyer Is dissolved, but, Of course, the gold
s untouched by the action OF any single
acid. The remaining pure gold is treated
with stronger acid, called parting acid"
to drive or any suspected trace OF silver,
and then washed with water. IL the
parting OF the gold from the silver has
been successful, the gold IS left as
thin, small sheet From this all moisture
IS driven off by heat. On weighing. the
gold may be as heavy as .O0O OF a
gramme. Then. as e. has previously been
noted that the total gold and silver bead
had weighed .00l5 Of a gramme, the
weight Of silver present must have been
.cVQ9 OF gramme. Inat IL 10 say, In one
assay ton OF 326es7 grarnmes there are
.0c1 gramme OF gold and .0OO9 gramme Of
silver. It has been stated at the COM
rnencement of this article that in an
assay ton each .00i OF a gramme repre-
sents In a real ton one ounce. Therefore.
we have seven tenths of an ounce OF
gold-that is, II pennyweights GO dwt.--
] ounce)-and nine tenths OF an ounce of
silyer--that is, IS pennywe!ghts. to the
ton. Quod eTat faciendum.
Many minor processes. such as roast
ing scorihcation, and inquartation, enter
into the work done In an assay; but II
has been desirable TO make the process
as ckar and free from complication as
possible. and for this reason a simple ore
has been selected. OF course. the results
Obtained from two assay tons assayed
simultaneously ought 10 be coincident
with one another. and this is why two
assay tons have been supposed 10 bo
treated together IN the above explanation.
cough IL not Ike a fever. II does nor
have 70 run certain course. Cure Il
quickly and efrectuaIly with One Minute