Gold Hill daily news. [volume] (Gold Hill, N.T. [Nev.]) 1863-1882, 1865-12-05
ALKCTURR
On silver Ores, and their Modes of
a---- Reductions. -
LaE ~ -
Br ". 7. RICHARD, F. C.


CONCLUDED.
The methods BY which silver is extracted
from these ores are almost as numerous as
the ores themselves, and in order to decide
onthe best and most economical mode Of re-
ducing any particular ore, the first step is
obviously to obtain, BY chemical analysis, an
accurate knowledge OF its constituents, the
character and amount Of its stony matrix or
gangue, and particularly the Undertaking.
agents in combination with the silver. Pos
sessed Of this knowledge, the intelligent
miner or mill owner holds the key to the So
luton Of the question Of treatment in reduc-
ton. With a practical acquaintance with
the facts that perfect amalgamation can only
be obtained from ores Of the chloride or ma
tive silver, imperfect and tcdstefM amalga-
nation from unroasted sulphides, and no
dmaLoGmGtion at all from the arsenical, an-
timonial cupreons or plumbiferous ores OF
| silver, he is enabled Ut u glance 10 decide
whether his ore can be most adv~antageously
treated by the furnace or the amalgamator,
| or the two processes in combination, such rs
| calcining before amalgamation, or, where
much chloride or native silver exists, first
\ extracting all susceptible Of amalgamation,
and afterwards smelling the tailings with
lead, or submitting them to calcination and
the chlorizing action Of salt previous 70 re-
a~malgamation.
With an analysis Of his ore before him, the
| metallureist knows that carbon must be adj
ded, should the metal be found to exist in the
state Of oxide, in order to reduce it TO the
metallic state. When sulphur is found to be
the Undertaking agent, it suggests the neces-
si,y Of adding some substance which has a
| greater affinity for it than silver, such as
ine or iron, il the reduction is TO be effected
by FIRE, or calcining with salt previous to
| amalgamation. When arsenic or antimony
are found in combination with the silver, it
is hopeless to expect any results from ANAL
gamation without previous calcination and
determination with salt. When lead or cop
per are found to exist in paying proportions,
the ore must be treated for those metals, and,
as the silver accompanies them through all
their various stages Of reduction, it is separ-
ated by a subsequent process.
The methods at present in use for the re-
duction OF silver may be divided under five.
heads, each Of which may be modified by the
proportion Of foreign matter present in the
ore. cost Of fuel, or mercury, or other circum-
stances.
The first, and simplest, is that Of smelling
the native and chloride ores with All alkaline
iux, in black lead crucibles. The rich sui
phides NAV also be treated BY this method BY
the addition Of metallic iron, to remove the
sulphur. By this process | have succeeded
in reducing rich specimens Of sulphides with
in two per cent. Of their assay value.
The second process is that OF amalgamat-
ing the native or chloride ores when too
poor /; that is, containing too much gangue or
earthly matter to admit of their becoming
economically smclted per Sc. The sulphidcS
are also imperfectly reduced by this method,
as practiced BY the patio system in Mexico
~ D.. III ,bn nu,a1v,pNnRi mana nf
Nevada.
The first operation, in this process, is to
grind the ore to an impalpable powder by
means Of stamps, ,rapiches, a~rastras, or any
other mechanical continuance that will insure
4 perfectly impslpable powder, Us amalgama-
ton will not take place till the ore has been
reduced to this condition, and many serious
failures have resulted from the neglect Of
this very essential point. II the patio system
is to be adoped the ore is spread out in the
condition Of n soft mud, on a paved floor,
called By the Spaniards the patio Tor cfrco,
when Of u round shape,), as at the the mines
of Ccrro de Pasco, in Peru. Mercury is then
filtered into il BY means Of straining through
a cloth, and ut the same time scattering it
over the entire surface Of the patio Tor circo),
which at Ccrro de Pasco is thirty-ninc feet in
diameter, aud contains eighteen to twenty
IOuS OF ORC " IuC ClAIRCp auu AS ouboS iSNA
inches on the floor. Salt and magistral Tor
sulphate Of copper) are then introduced in I
solution, in proportions Qike the mercury,
regulated BY the quality Of the ore being OPP
Grated on, and the whole incorporated BY
being trodden in by men or horses, for six or
eight hours per day, till amalgamation takes
place, which is usually thirty days in Sum
mer and often as many as ninety IN Winter.
When amalgamation has been completed,
which is known BY the thickening Of the mer-
curry, which is examined from time to time,
the contents Of the circo are drawn off into
large watts or settlers, where the amnlgam
subsidies during a gentle Sgitation, accompa-
MED by u stream Of water which gradually
carries off the tailings, or ~relareS, AS they are
termed BY the Peruvians and Chileans. The
excess OF mercury is then strained through
chamois leather or linen bags, and the ANAL
gam distilled under the capurse (or BILLY, BY
which the mercury is collected, per deScertunI,
in a vessel Of water under the hearth. The
loss Of mercury BY this barbarous system OF
distillation is only equaled BY the loss in
amalgamation. The aggregate loss, as ad-
mit,ed BY Peruvian miners, is one pound OF
mercury to each marc Of eight ounces OF sill
YER obtained BY this process.
As these Peruvian ores contain much sui
phide Of silver, like those Of our Comstock
lead, | may here describe the rationale OF the
process BY which the unroasted sulphide OF
silver is reduced through the agency OF sui
phate Of copper, salt and mercury. Ihe SAT-
sulphate Of copper usually decompose each
other, p~rotochloride Of copper and sulphate
Of soda being produced-whilc the metallic
silver present, or reduced by electro.chemical
action, decOmposes the protochloride OF cop.
per, and BY reducing it to the condition OF
= = =. ..-lf ~~NArk tnHN eha rhln.
ride Of silver. The subchloride OF copper
thus formed reacts on the sulphide Of silver,
forming sulphidc Of copper and chloride of
silver-the mercury, in its turn, acts on the
chloride Of silver, forming subchloridc OF
mercury, while the liberated metallic silver
combines as an amalgam with the excess OF
mercury. The indispensable condition OF
chlorinizing the silver is thus complied with
through the friendly intervention Of sulphatc
OF copper, which acts us an immediate agent
in transferring chlorine from sodium to sill
yer, so as 10 allow the latter TO amalgamate
with the mercury.
The process now in operation in Nevada,
although conducted on the same chemical
principles as that Of the patio, is n gigantic
move in the right direction, although much
remains to be done before we can escape the
reproach Of throwing away thirty per cent, OF
our precious metals.
By amalgamating in iron vessels instead Of
on paved floors, we have reduced the loss OF
mercury aud consequent amalgam to a mere
fraction (about one pound to n ton OF ore OPP
Grated on).
BY trituration, with heated mercury, we
have reduced the time Of amalgamation from
sixty DAYS TO less than six hours, and the ag-
vregate loss Of silver from fifty to thirty per
cent. or less. -T.'a.s -
The third method is that known as the
Freiberg proeess-the essential characteris:
tic Of which is the roasting or calcining Of
the ores with salt, so as to thoroughly chic
riuize the silver previous to amalgation. The
Freiburg ores usually consist OF the sulphide
Of silver, mixed with %sulphides Of arsenic,
anthony, iron, zinc, etc. 1t is important
| thew should not contain more than five per
cent. Of lead or one per cent. Of copper, a.
these metals greatly interfere with amalga-
nation; they analgamate with mercury as
readily as silver aud render the amalgam
very tough, besides producing the effect
known as the "sickening" Of the mercury,
which greatly diminishes its action on the
silver. ..
The prepared ground ore is FIRST spread on
the hearth Of the reverberatory furnace, and
J,;aJ with incesRant turning Oyer-then the