The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1919-09-11

ranged as it had been used by tn
: Federal company, except that the fin
Jlgs were cut out and their feed wa
sent to the 'slime-house', containing
the tables, vanners, and flotation ma
chimes. During this run various grad
es or products were made, as shown
in Table 2. 1t is interesting to com
pare the jig-tailings of the variou
sizes with the hand sorted tailings
in Table /.
From 1900 tons of feed, assayin,
LIB per cent lead and 0.75 ounces sill
Yer per ton, containing 20.76 tons o
led and 900 ounces silver, SO tons o
shipping product was made assayins
1913 per cent lead and 4.24 ounces sill
yer, containing 1927 tons of lead ant
1852 ounces of silver. This correspond.
to the extraction of 49.4 per cent o.
the lead and 1855 per cent of the sill.
yer The net smelter-v value eff this
shipping product was $14s6 or $1.24
per ton of feed With lead at 4.5c
per pound, and silver. at so cents pei
ounce the value would have been Sc
cents per ton of feed. The mill treat
ed 600 tons per "a hours
Upon this showing, remodellng the
mill for failing treatment was author
lied. The principal change was the
removal of the fine jigs from the main
building, thereby providing space for
tables and flotation machines and ell
iminatig the slime-house. This made
the plant compact and dispensed with
one operative per shift. Screens of 20
mesh were included in the trommel
system and adequate classifying equip
ment was provided. Plans were made
to place conveyor along the roof of
the mill in order to transport failing
from the dump to the feed storage
bins, using mechanical eXcavator to
supply failing to the conveyor. There
ever, and the arrangement of the rail-
way tracks suggested this as temp
orary means of feeding the mill. The
shovel was placed in the pit abandon
ed by the railway company and ar
rangements were made for transport
ing the failing to the mill at a fixed
price per carload Mechanical
TROUBLES with the shovel and trans
portation difficulties made this method
expensive and unsatisfactory, there
fore the conveyor as originally plan
ned is now being build.
THE remodelel mill was started in
December, 1918. and has been operated
since on a basis of two S-hour shifts
per day. No real difficulties has been
encountered other than those due to
excavating and Transporting the mill
feed, but these have naturally affected
the mill efficiency unfavorably. 1t is
expected that the conveyor will solve
most Of these difficulties.
'"The grade of the product and the
lead extraction have been practically
the same as in the test, but the sill
yer extraction is now slightly higher
than that of the lead.
When running at full capacity for
"a hour per day, with the cost of ex
duced to a few cents per ton by the
use of the conveyor, the estimated cost
of 25 cents per Twill be achieved.
"Ore from the leases in the old Last
1t. 10 he
mill in small lots aggregating from so
to 400 tons per month per lease The
mill is now receiving ore from eight
leases, and as storage consists of four
bins of $50 tons EACH frequent runs
must be made on this ore in order to
provide separate storage for each lease.
"The Bunker Hill company does not
buy the ore, it acts only as a milling
agent, and after deducting royalty
and milling charges, turns the proceeds
of milling over to the lessees. The
equitable distribution of these pra-
ceeds presents an interesting problem
It would naturally be supposed that
bins could be provided for storing the
concentrate belonging to each lease
SO that the concentrate may be ship
Fed and settled for accordingly. This
method is impracticable because the
flotation concentrate cannot be sue
cessfully settled with Jig concentrates
on account of the large volume of
water required to carry them. Also,
the large circulating load in the Dorr
thickeners feeding the flotation plant,
wecludes any sharp division in the
pulp from lots fed to the main mill.
the jig-beds, sumps, ano
launders contain a large quantity of
lead In material that is constantly
shifting, so that it could not be iden-
titled as belonging to any particular
lot. The only solution of the matter
was to combine the concentrates from
the treatment of all the lease ore and
depend upon automatic samples of feed,
concentrate, and failing of each lot
of lease ore to determine the distribu-
ton of the final proceeds. The me-
thod involves considerable mathema-
MATES, but has solved the problem
satisfactorily. The application of this
method to actual conditions is given
below
TT 10 gratifying to find that the