The Alaska daily empire., 1920-02-09
OF MILLING COSTS
 IN LOCAL MINE
Mining Journal Publishes Ar ticle Explaining Alaska
 Juneau Improvements

Milling costs have been materially reduced by the Alaska Juneau Gold Mining Company,
 At the same time improvements have been made which will increase the capacity of the mill up to the
 tonnage of ore originally promised for it. ffa.N New trestlies have been built re- gently, and according to an inter- view with F. W. Bradley published in the Engineering and Mining Jour nal for January, the improvements undertaken will prevent slate and
 other waste from going through the
 mill. The mining journals article reads asfollows:
 "Operating costs will be decidedly , reduced by sending to the changed and converted ball mills only such feed as has passed Pin. griZZley," said MT Bradley. These screenings
 consist of the most friable portion of
 the ore and they will be reduced by | the ball mills in closed circuits to ! fine pulp, thus eliminating the tube mills from the flow sheet. h.
 creased capacity and lower operating
 costs will be gained by the rejection
 of waste at two points, namely, be- i tween the jaw and gyratory rock cIrIsher and over the 50-stamp pilot mill bins. Between the two rock crusher units there will be installed shaking griZzleys which will deliver all the plus-six-inch discharge from
 the jaw crushers to short sorting
 conveyors located over the gyratOry
 crushers; and from these conveyors ] all quartz will be pushed off into the
 gyratory and all waste oversize will
 continue on out through the mill or
 conveyor to the waste dump. The
 undersize from the shaking grizzlies
 will bypass the gyratory crushers and unite with the gyratory dis
 charge. This combined stream of crushed rock and screenings is then
 conveyed to a point over the ball I mill bins where it is again grizzlied
 the undersize going to the bins as l ball mill feed and the oversize con
 tinuing on to the 50-stamp pilot mill
 where it is trommeled, to screen out
 any remaining small material; washed, to prepare it for sorting,
 and then sent to picking belts from
 which the quartz is pushed off for
 stamp mill feed. The waste con i tinues on the same belts through the
 mill to the waste dump.
 At the end of the year all the sort ing equipment over the stamp mill was in operation; but to make the whole installation complete. there yet remains to be installed the shak- ing grizzlies and waste conveyors in
 the coarse crushing plant.
 "The waste from the waste dump
 will be loaded into Granby-type cars by apron feeders and then dropped by gravity to the beach over a dou-
 ble-track tramway 2,000 feet long for final disposal. This tramway is con structed on an per cent grade to
 the beach and will be operated by a double-drum hoist controlled by q
 l50-hp. motor. At the end of the
 year the tramway proper was about
 75 per cent completed and the load
 ing platform and hoist installation
 were we'll under way.
 After the foregoing has all been accomplished there will then remain
 some refnements to be worked out
 in the concentrating flow sheet in or.
 der to increase the recovery of gold, ! lead and silver contents of the pre-"