Weekly journal-miner., 1918-03-20
(By P. R. Milnes)

f per ton i. O. D. cars blueDcll Sldlns.
 The Dc Soto mine is worked
 through a 20OO-feot adit which cor
 responds to the 6W-foot level of the
 mine. Five levels have been opened
 above the. adit and two below it, and ! the mines production of l50 tons per ! day is hauled by mules from ore | pockets on the adit level to the bins
 at the upper terminal of the aerial tram, a distance of 2300 feet. The
 tram line is 4OO0 feet long and oper-
 atcs by gravity, there being differ encc in elevation of 1000 feet between i the two terminals. In addition to
 overcoming friction and pulling up ] the empty buckets considerable en- ergy is absorbed by brakes. This en-
 ergy will shortly be utilized as electric
 power by gearing motor to the bull wheel, which motor may be reversed ; and operated as generator deliver 7 ing as electric energy the surplus i power which serves now only to 1 heat the friction brakes.
 The De Soto orc bodies vary in : length from 50 to l20 feet and in width from , to 40 feet. The walls | stand firmly and ''shrinkagc" stoping ] is the only method employed. The mining cost. including development, sorting and tramming is S2.55 per ton; : freight to Humboldt (25 miles dis tanD is 70 cents, making the orc cost i S3.25 per ton f. O. b. Humboldt Both ! at Bluebcll and De Soto the ore IS 1 run over sorting belt before load { ing and from to / per cent of the ; tonnage discarded as waste.
 Concentration
 ! At Humboldt arc the conccntrat- i ing mill and smelling plant. The l conccntrator, capacity 500 tons per day. treats exclusively the more silic- | ious ore from the Blucbcll and De i Soto mines. No custom orc IS millcd I md the oxidizcd domestic orc and moro basic domestic orc arc likewise sent direct to the furnaces. The De
 Soto orc is all very silicious, con-
 aiming o5 up 75 per cent insolublc | md is all sent to the conccntratof, | put much of the Bluebcll orc Is quite | basic and it is more profitable to
 ;mclt the Blucbcll orc directly when he percentage of insolublc runs be- | low 9. This is particularly the case since the precious metal values arc | greater in the moro basic orc and the | recovery of these IS better in direct | melting than in concentration fol-
 owed by smelling.
 The ore is delivered in bottom Jumping railroad cars at the top Of the conccntrator building and dis
 charged into a l25 ton bin supply 1 ing the crushing plant. A short con vcyor belt takes the orc to l2x24 inch Blake type breaker that reduces ] t 10 } inches. The breaker product | discharges on to O-inch conveyo,
 belt leading to the Symons (4S-inch | diam.) disc cruShcr This convcyor
 is equipped with a Ding magnetic | pulley to pick out drill bits, hammer | heads and other iron and steel pieces that would otherwise find their way into the Symons crushcr. In spite | oi this prccaution steel occasionally gets into the cruShcr causing choke | ups that require from half an hour to several hours to clear and threat
 cning always serious damage to the
 machine.
 From the Symons crushcr the orc crushed to l inch. discharges into al
 bucket elevator which raises 1t to al 7x3-foot trommcl covered with H-I inch punched plate. The undcrsizc isl conveyed by 20-inch belt to the
 6OO-ton crushed orc bin furnishing
 storage for the concentrating sec ton. The oversize drops to a sell of 4Oxl6-inch Anaconda type rolls set to Il inch and the discharge of rolls is led to the bucket clcvatorI
 mentioned above. The oversize isi
 thus kept in closed circuit with the
 rolls until crushed fine enough to-
 pass the trommcl screen whcrcuponl
 IL lS convey Cu lO lllN NluSiiSu ciN Diii'
 From the crushed ore bin the orc
 now reduced to !. inch Is drawn as
 required for the ball mills by two
 apron feeders discharsing onto a
 20-inch convcyor belt. This belt
 runs over Mcrrick wcightometcri with automatic register recording the
 tonnage passed over it. At the head
 of the belt is a splitter to proportion
 the feed as desired between the two
 ball mills. One ball mill is an -Allis
 Chalmers 6X6-foot cylindrical mill
 from which the grating at the dis
 charge end has been removed. The other is a HardingO mill feet by
 2 inches. Both mills are driven by
 spur gears on countcrshsftS belt
 connected to motors and grind in open circuit, treating together about
 t5o tons daily The ball mills dis charge is elevated to an S-foot Cal! decott cone for classification for ho-