The sun., 1899-03-05
THE FIRE TEST FOE ORES
How tho Assayers Determine tho Value OF
Samples from New Mines.
F.o,, n. D<,,,r T;r,,


From the Denver Times.
Tho process Of ascertaining the value OF a
piece OF mineral bearing rock is interesting.
The ore Is first pulverlzed in crusher or NOR
tar. 1t is then quartered or split until q sam
Pile Is obtained small enough for convenient
handling. split " is a series of troughs al
ternating with q series Of slits equa! in number
and size to the troughs, Half OF the sample is
retained in the troughs every time the ore Ia
passed through the split This process is re-
peated until the quantity Is sufficiently re-
duced. The sample thus obtained is spread
upon "bucking board" metal plate fastened
on a firm foundation. 1t is then reduced to
powder by rolling it with muller" which is
a heavy iron sledgc with a smooth convex sur
face. The sample is usually pulverized until 1t
will pass through sixty mesh. or sometimes
The, assayer uses weights which are proper
@ 81 fh Of
used each mieram I'M in S the res result fE represents @
an ounce Of the precious metal to the ton.
hs fP Is by
the number OF ounces to the ton.
A half assay ton OF the pulp is weighed care
together with a .fiux The fiux consists OF car
Donate OF soda; boraH and litharge. or or protoxide
eordinG to the nature Of the ore. Some heavy
Other ores which contain little or no lead re-
auire litharge In larger Quantities: The pulp
With salt or borax Borsx makes clearer Aux.
but has no other advantage over the common
salt II hsFe Is a6de3 az hS OF sTha the
placed In the furnace. which has been heated
to white heat to receiv it,
muffie. which is made with an opening at the
back to permit the fumes from the crucibes to
is required to reduce the contents of the cruc;-
bic to q volatile state, When the action in the
into a metal mold and al lowed to cool The Stag
is then broken on and LEAD button ia found at
ths s as eod me 6s
separate the gold and silver from the lead the
bptEn Is In Sup II sma dSh mSds
while part Of It Is absorbed. together with apy
button in the c9pel. il the, ore Is known e
in the cppel Just as it is taken from the Stag:
but If there is very little, silver In, the ore. a
s Is sxst 10
button obtained In the cupel. This is neces;
sary In order that the button may be parted
The silver button is weighed on the button
balance and is then parted by immerSing It In
leaves the gold in the form OF fine black dust.
The parting is done IN an anneallng cup. The
ROlQ Is WuSnou anu uTl0u anu tne cup lS placed
In the mufie and heated to a red heat. which
anneals the gold: bringing 1t into comgSet
gold is trahserred to It the tray sV on % the button
balance and weighed. Tho weight OF the gold
Is deducted from the the weight h 9f the silver but
The button balance is an exceedingly deli
cate piece OF mechanism. 1t Is kept In elhss
case. and the weighing is done with the case
closed. In order that the air currents in the
room may not affect the beam. The balance is
30 delicate that the vibrations caused by per-
son walking across the room near them will
affect the result. strand OF maiden hair will
turn the balance as II it were young mans
head. The gold and silver are weighed to
miIlgrams. and and even to hupdredths OF a
placed on the balance with small pincers. In
order that the hands may not comet In contact
with the parts OF the scales. tor the tenn pera-
accuracy.
n the gold obtained In the assay just de-
scribed weighs 100 milligrams. the ore carries
200 ounces OF gold to the ton. which is good
enough for any ordinary mine.