The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1918-05-02

The Annual Milling Number of
the Engineering and Mining Journal
contains an interesting contribution on
the flotation process as practiced by
the mines Of the Occur d'Alene district |
by Claude T.. Rice. who spent several
weeks here making close study OF
the operation of the system In the va
rious mills. Numerous Illustrations
contribute to the interest and value
of the article. and in the pictorial Sec
ton of the magazine there are excell-
emit half page illustrations Of the Her.
cules and Federal mills at Wallace, the
Hecla mill at Gem and the Morning
mill at Mullan. Part Of Mr.. Rice's ar
ticle is here reproduced:
Relative Value Of Fiotatien.
Flotation is now an integral part of
the milling practice of the Occur
d'Alenes. This is true in the district.
whether the ore is predominantly
sphalerite or galena, or is one in which
both sulphides are important; it does
not matter whether sulphides occur
disseminated in fine grains ore in large
sized crystalline aggregates In the
gangue (quartzite). Flotation. how
ever, plays relatively small part in
the average flow sheet of the district
for the practice at present is to first
obtain as much of the valuable min
eral as possible by gravity concentra-
ton, after which the tails are retreat
ed in frothing machines. At most of
the mills even the finest shines are
first sent to tables or vanners before
treatment by flotation, although the
recovery by flotation of the galena in
most ores of the district is high, es
pecially IL little siderite is present.
This supplementary application Of
the flotation process is due mainly to
three causes: First, the uncertainty
which now prevails in respect to the
flotation patents; second, the lack of
confidence which many of the millmen
have in flotation, owing to erratic re-
suits obtained in the district, which
pi eclude sole reliance upon flotation !;
third, the instructive realization of the
Importance of catching the valuable
minerals as early in the milling pro-
cess as possible. The last Is by far
the most important reason that more
reliance is not placed at the present
time upon flotation in milling Occur
d'Alene ores.
Occur d'Alene milling practice is
therefore still in a transitory stage in
;, respect to flotation, and the relative
Importance Of that method in the mill
;, ing of the ores of the district depends
mainly upon four factors: the royal
ties that may be demanded for the use
q of the process. the prices prevailing
for silver, lead and zinc after the war
the progress which may be made in
obtaining lower zinc in lead float
and lower lead in the zinc float es.
:, pecially after differential flotation
and, finally, the advances that may bt
made in the hydrometallurgy of LEAD
and zinc But whatever process is fin
ally used In the treatment of the ores
it is reasonably certain that the great
s er part of the galena will be obtained
. by gravity concentration. since mucl
of the lead is coarse and fully so pei
cent of it can be saved on jigs ant
:, tables, the only exception to this con
dition being the fine grained ores.
= The saving of blende by gravit!
methods is not as good as that of ga
lena. There is often siderite in tn,
ORE as that at the Morning mine, t.
!, prevent the recovery of the blende II
:. marketable form by simple gravit.
: methods. But even in the case of thu
: finer grained ores gravity methods will
;, continue to play an important part II
. the mill treatment.
!, The flotation process will during thu
: next few years increase considerabl!
in Importance in the milling method.
of the district; for flotation, because
j, of it's so-called "selective action" upor
), the silver minerals and on account O
: of shines. assists, even now, and viii
. do more in the future in the treatmen
of Occur d'Alene ores when 1t is better
y, understood. Already many of thu
!, companies that are treating ores II
which the valuable mineral occurs ir
coarse grained aggregates are begin
:, ming to realize that by finer grinding
:, of more Of their table middlings ant
. the treatment of the resulting slime II
!, flotation machines they can make mo-
:, only higher recoveries but also win
greater profit from their ores.
With an increase in the zine content
!, in the ore, flotation increases in i'm
portance in the milling scheme. since
with such ores 1t becomes difficult tC
treat at profit by gravity methods
when the metals are at ordinary prices
Selective Action Of Flotation for Silver
: In the Occur dAlenes much is said
e about the "selective action" of flota-
! ton for silver. This is because the
A proportion of silver to lead in the
: flotation froth is high as compared
Y with other concentrates. But this is
0 not so much because Of selective ac-
ton shown for silver minerals as 1t is
l that the flotation froth catches slime