The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1919-09-25


process of producing spelter, hence the
zinc mine operators have had to meet
the terms of the zinc shelters in re-
gard to the following requirements:
~ Minimum percentage of zinc the
ore must contain; (2) the chemical
combination of the zinc in the ore;
go the proportion present of those ele-
ments that interfere with the Sec
cessful recovery of the zinc when the
ore is retorted. In consequence the
zinc ores mined can be shipped d.
rectly to the shelters.
Under normal conditions the low
limit of zinc in ores suited to retort
smelling is about % per cent for oxi-
died ores and about 35 per cent for
sulphide ores. Consequently the ores
or products suited to zinc smelling in
retorts may be obtained from
1. Zinc ores free from interfering
elements.
2. Concentrates or zinc ores or Of
zinc-lead ores.
3. Concentrates of mixed and COM
MEX ores, containing gold, silver, lead,
copper, zinc, etc.
The zinc produced from ore mined
in Missouri, Kansas, Illinois, and Wis
consin comes from sulphide (blende),
carbonate, and silicate of zinc. The
zinc produced in Utah and in Idaho,
Montana, Colorado. and Nevada is
largely from lead-zinc ores, the zinc
being separated from the lead when
the metallic minerals of the ore are
separated from the worthless gangue
nv some form of mechanical concen
tration.
A large part of the valuable min
eral content Of the ore Is lost in effect
ing this concentration. AS result of
the other requirements that have to
be met in zinc smelling, much zinc
is lost in the mining and milling of
zinc ore.
Losses in Mining.
In mining the ore the zinc losses
aggregate a large tonnage. These
losses are due to several causes. For
instance, the average western lead
mine the zinc ore remains as a shell
around slopes from which the oxidiz-
ed lead ores have been taken. In most
mines the lateral extent of these shells
is unknown, and as they generally
carry too little metal to warrant mil
ling at present, they are not removed.
Later, the lead-ore slopes are filled
with waste and the zinc in these sur
rounding shells is lost
Losses in Milling.
AS only small proportion OF the
zinc ores milled in the United States
contain enough zinc to warrant direct
smelling, separation of the valuable
minerals from the gangue by some
method of mechanical concentration
is generally necessary.
For the sake of convenience. the
concentrating processes used are con-
sidered herein in the following order:
/. Hydromechanical process.
2. Electromechanical processes.
(a) electromagnetic.
CO Electrostatic.
8. F'lotation processes.
Hydromechanical Processes
In treating zinc ores by hydrome-
chanical processes the object Is to OBJ
tain a concentrate that, If necessary,
NAV afterwards be separated into
zinc product and lead product, or
into a zinc product and product that
may contain lead. copper, gold ana
silver, and is sent either to LEAD or
copper blast furnace
AS stated previously. large proper
ton of the zinc and lead minerals Is
often lost in the failing when any ore
mined for it's zinc or lead content Is
treated by hydromechanical concen-
tration. AS one Of the functions OF the
Federal bureau of mines Is to conduct
investigations looking to the preVen-
ton of mineral waste, the bureau mas
for some time been conducting inves-
LEGATIONS in the Wisconsin and the
Missouri zinc fields in order to ascer-
tain the causes of the losses IN mil
ling zinc in those states, and, If pos
sible. to devise improvements In the
processes used.
Wright gives the following inter-
esting data on the efficiency OF ny
dromechanical concentration in the
joplin district The ores require The
simplest form Of hydromechanical con-
centration.
Efficiency Of Concentrating Methods
in the Joplin District.
Quantity of ore thru mill. 30s.f'
Quantity of zinc concentrate
produced, tons .......'.''''' '''N'
Assay of zinc concentrate per
cent zinc .................. w.
Quantity of blende GINS, 81 per
cent zn) in concentrate, tons. S.lo
Quantity Of failing, tons. ...... .3oo'4o
sAssay of failing from mill (o'so
per cent Zn) per cent zns.'. L.
Loss of blende (ZnS) in falling
.. 429
Total quantity Of blende (ZnS)
in ore thru mill, tons...... lz'4z
Total recovery Of blende thru
mill, pre- cent ...........'.'. o'.'