The Goldfield news and weekly tribune. [volume] (Goldfield, Nev.) 1911-1947, 1914-09-12
HCLT-DERN PROCESS
SUCCESSFULLY USED
TREATMENT OF LOW GRADE
ORES AT MINES OPERATING
PLANT DESCRIBED

A detailed account of the new
process that is being successfully ap-
piled by the Mines Operating plant
at Park City has been written by
P. Holt, who is associated
with George H. Dern of this city,
says the Salt Lake Tribune. The
process has been applied to the treat
ment of the ore taken from the old
Slopes in the Ontario mine. This
ore carries from six to fourteen
ounces in silver, one to two pounds
of copper, .01 to .015 ounces of gold,
and a small percentage of lead and
zinc to the ton. The treatment con-
sists of mixing the crushed ore with
coal dust and salt and then roasting
in a new type Of furnace by COM
bustion Of the contained fuel. The
roasted ore is leached with an acid
solution to dissolve the silver, cop
per, gold and lead, and these metals
are precipitated together with scrap
iron, and the product in this form
is sold to the refinery.
The roasting process is the fea-
ture in this treatment plan, and
makes possible the chloridizing of
ores without any loss of the valu-
able metals, at a very low cost. This
roasting process had its beginning
in connection weth the research
work in the University of Utah
mines department, and N. c. Chris
Jensen, Jr., was largely responsible
for the working out of this prob
lem, while making experiments with
the base gold ores of the old Mercur
mine. After installing a small test
plant at the Mercur properties, Chris
Jensen disposed of his interest to
George H. Dern, and a considerable
amount of experimenting was con-
Quoted at the Ontario mine before
the present system of roasting was
decided upon.
The teaching process es very sim
pie, a solution being made of solu-
BILE salts from the roasted ore, carry
ing in addition about four pounds OF
free acid. The acid is in part sup
piled from the condensed rooster
fumes, the remainder being added
from sulphuric acid. At such times
as the ore carries a considerable per-
centage of pyrite no extra acid Is re-
quired. In conclusion, Mr.. Holt
says:
'The roasting process is not lin
tied to chloridizing, but may be ad-
vantageously applied to oxidizing
gold ores for cyanide treatment and
oxidizing and sulphatizing copper
ores for subsequent teaching.
However, it is my opinion that
the most favorable field of applica-
ton is in chloridizing roasting. In
this class of roasting we not only
have the benefit of cheaper operat-
ing cost, but, en- addition, have owe
come the volatization loss, which in
the past has been a serious difficulty.
1--WE have tested out samples OF
ore from thirty-eight different mines.
These have given us a large variety
of combinations. In many cases the
recovery of gold, silver and copper
has been we'll above 80 per cent. The
ideal combination, we may suggest,
is a siliceous copper-silver ore car
rying 6 to 10 per cent pyrite and
~favorably located with respect to a
salt supply. Under such favorable
conditions, the entire cost of mining
in a well-designed plant will be less
81 per ton, on the basis of $50
tons per day. When the ore carries
gold it is necessary to carry free
chlorine in the teaching solutions,
and this adds a few cents to the cost
of treatment.
Cores high in silica, iron and man
ganese chloridize readily. A small
percentage of lime does no harm, as
it is READILY n~eutralized in the roast.
A large percentage, however, is det-
rimental."