The daily star-mirror. (Moscow, Idaho) 1911-1939, 1921-04-02
LEADING ORES OF
THE COEUR D'ALENES
ASSISTANT METALLURGIST OF
SCHOOL OF MINES AND GOV
ERNMENT MAN WRITE.


By Clarence A. Wright (Metallur-
gical engineer, United States Bureau
of Miles,. James G. Parmalee CAS-
sistant metallurgist, and School of
Mines, University Of Idaho.)
The chief metals produced from the
ores of the Coeur d'Alene region are
lead and zinc with minor amounts Of
copper, silver, and antimony In
much of the ore the lead and zinc
minerals are SO finely disseminated
that the making Of clean lead and zinc
products by the usual methods is
impossible. At most of the mills
good percentage of both lead and zinc
is recovered in the concentrates from
the jigs, but fine grinding is essential
to effect a reasonably clean separa-
ton of either mineral when finely
disseminated; in fact, in an ore
crushed to 200 mesh some of the lead
and zinc particles are still mechanic
ally combined
The United States Bureau of Mines
In cooperation with the University of
idaho, the Idaho State Bureau of
Mines and Geology, and certain min
ing companies of the Occur d'Alene
region has done much experimenting
In order to find some method by
which a better commercial separation
might be effected. On account of the
,charater of the ores and in order to
avoid any radical changes in the
present methods or equipment in the
mills, cit was thought best to try to
effect a better separation of the lead
and zinc minerals by differential fro
tation with whatever changes in the
present treatment this might necessi- |
tate should it prove successful. That
is-the object is not to evolve differ |
ential flOtation process which would |
replace the present methods of gray
ity concentration, but rather one that |
could be applied to the relatively fine
material and slime produced in the |
mills and which are not being sue
cessfully treated by gravity methods
or by frotation. From large num-
Der Of tests run to date on different
ores, some encouraging results have
been obtained Although they are not
to be considered as final they indi-
cate that the separating of lead and
zinc sulphides by differential frota-
MOn may be practicable in the treat
ment OF certain ores. A report on the
results of these tests has recently
been issued as Bulletin 2O5 Of the
United States Bureau of Mines. The
report also contains a chapter deal
ing with flotation tests of a few cop
per and silver ores.
Method of Test
In conducting the experiments with |
lead-zinc ores the principal object has
been to determine the flotation mix
ture that would effect the best diff (
ferentia1 separation from a CONNER t
cial standpoint The actual testing of j
any ore was preceded by preliminary s
examination of the ore, /
screen analysis after crushing to {
one half inch size or less and examin- S
alton under the microscope Of the '
finer sizes to ascertain the fineness OF
crushing necessary to liberate most
of the mineral particles, followed by
chemical analysis of the ore and OF /
the products obtained from the screen t
analysis. The more important points S
brought out by this preliminary ex-
animation, considered with references
to subsequent flotation testing, arej n
the necessary degree Of fineness in
grinding, and the composition OF the
ore as to the minerals sought and the
gangue constituents present
In actual flotation tests, expert /
ments were made on each ore using :
different oils and chemicals alone, TO K
determine the relative value of each Q
as to it's flotative properties. Next t
various combinations of oils and Z
chemicals were tried, followed by II
tests using different quantities of the a
reagents. Besides oils and chemicals,
many of the derivatives of both min = =
,ral and vegetable oils, such as phe-
1ol, anthracene, engenol and guaiacol,
we're tried. Some of the oil deriva- >
ives gave good results. 1 !,
Flotation tests Of Idaho ores, by G.
A. Wright, J. G. Parmalee and J. I.
Norton. A copy of this bulletin may
30 obtained by writing the Director, :,
Bureau of Mines, Washington, D. e. :
General Conclusions il
With the lead-zinc ores differential IL
of the lead and zinc sui i1
,hides were effected with the lead t;
PRODUCTS assaying so to 60 per cent Il
cad and to 8 per cent zinc, and O.
inc products containing about 40 per W
,ent zinc and 4 to per cent lead, re- S,
covering about rs to 80 per cent of the
cad in the lead products and 80 to
IS per cent of the zinc in zinc pro-
lucts. These do not include cleaning p
ests. On the basis of the experiment a.
al work done, the following con- Sc
lusions would seem justified: CD A n
complete separation Of the lead and a.
inc sulphides by differential frota-
ion is not possible, owing to the in
innate association of the minerals.
p Fine grinding is essential in order M
0 liberate most of the sulphide le
ninerals and to permit separation. II
81 A better recovery is possible with fe
n ore that has been crushed wet Sc
han with one that has been crushed NJ
ry (4) A pulp density of between NJ
" and 3H parts water to | part a
olids seems to give the best results. re
81 Each ore seems to require some ht
What different flotative mixture and pl
he effect OF certain oil or chemical hi
n one ore may be different on some hi
ther similar ore (6) A better separ SC
ton of the sulphide minerals was kl