Grass Valley telegraph., 1857-02-21
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Important and fsgsafTy Interesting szperf-
ments for the thorough and economical ex-
traction of gold from its ores, have recently
Gec1 conducted, both ay eminent chemists
anu practical Miners III various palts of Eu-
rope. The results of these enquiries are
now before the world, and are exciting no
little degree of interest on both sides of the
Atlantic, especially among those engaged in
gold quartz mining
These researches and experiments have
been principally confined to two leading OBJ
Jects list. the utility, or economy OF roast
ing the ores in bulk, before crushing; and
I'd, to an enquiry into the nature of the au-
riferous pyrites, and the best mode of treat
ing them with reference to the extraction of
the gold which they contain. 1t is our pres
ent purpose to lay before our readers some
account of these experiments, and the con-
clusiOns arrived at among trans-mOntane and
trans atlantic miners. We propose to con-
slider first the
ROASTING OF GOLD ORES.
The economy of this process is a matter
which has attracted the attention of both the
scientific and practical miner for upwards of
two centuries. As long ago as 1929 Lazar-
us Erckern, the Assayer General of Ger
many, published work on gold ores and
metallurgy in which he took ground against
the practice of roasting" gold or silver
ores, for the reason, that careful experiments
had satisfied him that large per centage of
the metal was lost by the operation. Since that
time much has been written upon the subject,
and, until recently, very great diversity Of
opinion has existed among miners and scien-
tifc men in England and on the continent
Modern discoveries in chemistry have very
greatly Facilitated researches of this descrip-
tion, and such experiments are now conduct
ed in manner which dispels all doubt as to
the accuracy of the results and conclusions
arrived at. Under these favorable circum-
stances an elaborate series of experiments
has recently been fairly and fully tried I'M
der the auspices of the Russian Government
and the conclusions drawn therefrom are
very decidedly against the roasting process
The official report Of these experiments
which were conducted among the mines al
Ecatharinebury, states that the ore when
roasted in hermetically sealed crucibles lost
20 per cent of gold, and Al per cent of sill
yer. Ore roasted on an uncovered hearth
resulted in loss of forty per cent of gold
and tl0enty-One per cent of silver! The same
experiments were repeated at many different
mining localities. and everywhere with sini
lar results. They have also since been re-
peated in England, though in a less elaborate
manner, but still with sufficient exactness tC
satisfy the experimentors of the general cor
Fectness of the results given in the Russian
official report.
The following are the published opinion!
of several practical miners and metallurgist
who have devoted much attention to this sub
ject:
''Trehern. at Marmato, roasted the ore in
reverbatory furnace. and though the show
of gold was great it only yielded about ont
fifth of what was obtained from an equal por
tion of the unroasted pyrites.
Leay, at Marmato, roasted his ore ant
found he got less gold than he would hav,
obtained by the most ordinary method of th
Batea. He roasted his ore to that degree
that the color of the slime, which escaped il
abundance from the stamp pits, was deep RET
brown, or hematte red.' go
Again. he found one-third of the gold re
mained after roasting in some manner asso
ciated with the sulphuret of silver. and othe
products formed by the process of roasting.
Degenhardt has an opinion that the gOl
forms sulphuret and is perhaps carried o.
through the chimney, on account of the sill
yer, which formerly was alloyed by the gol
having entirely disappeared during the pre-
cess of roasting.
Philips in his 'Metallurgy,' says Gold
not directly attacked by sulphur at an
temperature but when fused with the a
kaline sui phurets, is rapidly acted on wit
the formation of a double sulphuret, in whic
the sulphuret of gold acts the part of a
acid.'
4 am fnlly impressed with the belief ths
the ore if ever roasted will cause you los
of that gold, which could have been muc
easier. ascertained by simply stamping it, an
causing it to pass over mercury or skins
--.NS. Correspondence.
Whether the loss by roasting results frol
the carrying away of the extremely fine pa
ticles of gold by the upward current of a
from the burning mass, as light breath
wind carries off the leaf gold in a guilder
room or whether some chemical change
the gold occurs by which it is oxydised; {
whether the loss results from sublimation 81