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4.-1767 T HE W O P. K S P R OGRAM *** --'\7or ks ?rogr e s s Administration-/ For Rel ease to NPwspapers, Sund[~ , September 25 , 1938 TEC3NICAL ADVANCES IN MINING ViAKE AVAILABLE LOW- GRADE ORES , OFFSET DEPLETION , AHD I NCRF.ASE OUTPUT PER 1.'iORKER Tlle mining industry in this country has long sinc e skimmed the 11 cream 11 of most of the rich mineral deposits and is now faced with the probl err of working grades of or e which a gener2.tion ago would have bea n conside r ed almost wort hl ess . The ingenuity and inv entiveness demunded by t h i c decline in or e . grades Las brought about great improvements in mi ning technique s . I n suite of decr Aasing metal cont ent :i::rn r ton of ore , t e chni cal progr ~ss har; pr od J.c ed 1 a rising output' per worker for all maj or metal s . Thos e facts arc brou 6ht out in a monogr i'..ph pr Pprir od. by the WPA Ncs ti onal Re s earch Proj ect in cooperation with t L: U. s. Bur eau of Mi ne s , and rel oas od for publica ti on t oday by Harry L. Ropkinc , Works Progr e ss Administrci,tor . the ti tl c , "Min~ffa1 Technolo gy and. Output per Ifan Studi es : Under Gr2-de of Ore 11 , it analyz os the effects of lowered ore y i elds in such miner a ls as gold , silver , copp er , lead c:,nd zi r..c . In transmitting the r eport to Mr . Hopkins , Corrington Gill , Assist.:mt Administro.tor in ch8.rgo of all research of the WPA , stat os that the declining grade of ore 11 has b een r persistent stimulus to the mini ng t ochr;ician. Eis inv entions , requir od to ~ ff set increasing physical diff i culties in mining , Di~zed by Original from NORTHWESTERN UNIVERSITY NORTHWESTERN UNIVERSITY 4-17 67 - 2 - have changed. the cours e of output of metal pe r man . "Despite improvements in t echnique , however , t here comos a ti1ac in the lif e of every mine when the yi elds of valuable content pe r ton of ore continuously fails t o return a p r ofit ; the mine then ceases to be an employer of l abo r and l eaves in it s wake the half-abandoned. camps t hat are found in mc:ny of t he ol d.er mining di stricts. Some of the effe cts of this depletion are found in t he heavy reli ef rolls of many west ern mining arGas who r e early vigor has waned , i n t he changing geographical distribution of employment opportuniti es for mine worke r s as mining shift s t o new l ocaliti es , and in the moclified. skills r equired by 1 mass mining 1 of low gr ade doposi t s with new va:ci e ti es of equi pment. 11 Also , when adver se economic conditi ons force reduc ed produc tion , em- ployment i s shnrply affected. a s ef fo rt :3 are made to r n,i se the yield by the s ele ctive mi ni ng of small to nne.gos of high- grade ore . Fo r exampl e , the repo rt points out t hat Mich igan copper mi nes r educed. t heir output of oro by 68 pe r cent b e t"\':e en 1 931 and 1932, and. raised. the yi eld. by 45 p Grc ent ·by moans of s el ective mining . This d.id. ::i.ot gr eat l y chcng,:0 the out put of coppe r per mD-n , but it rosulted in sharp changes i n employwen;; sinco the iilc'.n- hours worked u nderground we re cut 72 percent . 11 Tho study go0s into the subj ect of tho general decline of ore grades , pr ofaced. by a bri 0f a_osc ri::::i ti on of early 11 bonan za 11 mi ning whon a pick nnd shov 8l wo r e tho :::n·i ncipal it ems of equipment , and di scusses t ho t eclmi cal advances which have made poss ibl e the profitabl e working of low- gr ~de or es . Seriaro.te chap t e rs ar 0 devoted t o gold and s ilvsr ores , coppe r, a.11.d l ead and zinc . In a final chapter on output per m/),n it is po int ed out t hat ap~Jr oxi mo,tely one- half the Nation 1 s present c0pper suppl y comes fr om mi nes which were known Digitized by Original from NORTHWESTERN UNIVERSITY NORTHWESTERN UNIVERSITY 4-1767 -3- but considered worthless in 1900; tha t silver and gold. deposits with one-tenth the yield requir ed for profitabl e production 50 years ago are b eing successfully worked today , .'.lnd that in spite of a 27 percent decline in ore yields in l ead mines in the last quarter of a c entury , such depo sits are still being worked at a profit. "Meta l mining, 11 the r eport stat e s, 11 ha s had to adjust its elf to a lower grade of or e , and the success of this pro cess has b een one of the impo rt o,nt victori e s of miner al t echnology . 11 The r e~ort consists of 114 pages , including an appendix of numer ou s cho.rts and suppl emental mat eri al . O. E. Ki essling. It was prepared by Andr ew V. Corry and Dr . Ki oessling , of tha u. s. Bur eau of Mines , is in cha rge of the miner a l technology studies of t he Nati onal Res earch Project on Reemployment Opportuniti es and Recent Changes in Industrial Techniques directed by David Weintraub and Irving Kaplan. ---0--- Digitized by Original from NORTHWESTERN UNIVERSITY NORTHWESTERN UNIVERSITY
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