The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1919-09-11
Treatment of Tailings and Ore in the
Sweeny Mill at Kellogg

II. S. Handy, superintendent of mill
of the Bunker Hill & Sullivan com
pany, has an interesting contribution
August 20, in which he describes il
detail the method of sampling tn,
great Sweeny dump. the remodellint
of the Sweeny mill to successfully
treat the failing, and the manner O
distributing the products of the mill
which is used for treatment of botl
the tailings and the ores from thu
various leases on the old Last Chance
mine. The article is largely techni.
cal and Is accompanied with diagrams
showing the composition Of the dump
flow sheet of the mill, elaborate tables
etc. So much of Mr.. Handy,s article
~ Is practical for tn Miner to repro
duce is given below, and it will be
found of great interest as showing the
possibility of probable mineral recov-
cry from material heretofore regarded
as waste:
1.-THE Sweeny mill near Kellogg,
Idaho formerly belonged to the Federal
Mining & Smelling company and was
used by 1t to treat ore from the Last
Chance mine at Wardner. Following
the operation Of this mill there remains
a dump containing about 100000 tons
of tailings assaying 1.s9 per cent lead
and 0.73 o. silver per ton, represent
ing 22,194 tons of lead and $4,000 o..
of silver The deposit is nearly 20
feet deep at the apex and covers about
20 acres of river-bottom.
During the period of Is years in
which the mill was operated, four
successive layers of failing were depos
tied. Dump No. was the earliest and
smallest deposit, and the succeeding
layers increased in size but decreased
in lead and silver contents
when, in July 1918, the properties
of the Federal company at Wardner
and Kellogg reverted to the Bunker
Hill company on account of the eX-
haustion of the Last Chance ore bod
ing the Sweeny mill for re-treating
failing from this dump was investi-
gated. The only other material avail
able for the mill was small lots of ore
from the. leases in the old Last Chance
workings.
'@The tonnage in the dump was es-
timated by running lines at intervals
of ESQ feet at right angles to The rail-
way track along the foot Of the dump
and making cross sections on vertical
planes following these lines. From
intersections of the surface planes of
the several layers with these vertical
planes, the cubic content and tonnage
of each layer of failing was calculated.
The material weighs 10 lbs per cubic
foot.
lowing to the depth of the deposit
and the nature of the material COM
posing it, an average sample of the
whole dump could not be taken, but
1t was possible to get good samples
Of the various layers where they were
exposed and could be identified The
sampling was done in this way, princi-
pally in open cuts, but in a few fav-
orable places shallow shafts were sunk
for sampling purposes. The average
assay Of the WHOLE dump was derived
from the tonnage-assay of the several
layers Decrease of richness as milling
methods improved is clearly shown by
the sampling, the first dump assaying
234 per cent lead and 100 ounce sill
yer per ton, whereas the last layer as
says 1.5O per cent lead. and 0.5 ounce
silver per ton.
Laboratory tests were made on
composite sample representing the
whole dump. The material was screen
ed and sorted by hand into the pro-
ducts shown in table l. No attempt
was made to sort the material below
2O-mesh, the assumption being, from
former experience, that about so per
cent of the lead and silver in this
material could be saved in tables and
by flotation. The tests indicated that
SIS per cent of the total material was
of a suitable size for jigging, contain
ing 81 per cent lead and 70 per cent
of the total silver. About rs per cent
of the lead and silver contained in
this portion of the sample was extract
ed in a product called jig -middling',
assaying 42S per cent lead and 1.5
ounces silver per ton, leaving 70 per
cent of the weight in the form OF
failing assaying O.56 per cent lead
and OF ounces silver per ton. The
jig-middling carried 20 per cent OF
iron over insoluble. making 1t prod
uct desired by the smelters for use as
fux. At the high metal-prices then
REVEALING this was satisfactory ship
ping product. Tests on the same gen.
eral sample with the jig in the labor
tory confirmed the hand-sorting tests.
at was assumed that the mill would
treat 500 tons Of the failing per "a
hours and that the milling costs would
be as follows:
per per
Labor: day ton
/ foreman at 81 per days 100
mill men at $5.25. ....... $3.50