The Mining Magazine, Vol. 49, No. 1

r - w ». - ¡ J L

Mining Magazine

M anaging p.. c

l?ector and E ditor : W . F . W w t e . A ssista n ts : S t. J . R . C. S h e p h e r d . A .R .S.M ., D .I.C ., F .G .S .;

p F . H ig h a m , A .R .S.M ., M .Sc., F.G .S.

u * U s HED o n t h e I 5 t h o f e a c h m o n th b y Mi n i n g Pu b l i c a t i o n s, Li m i t e d,

Telephone AT SALISBURY HOUSE, LONDON, E .C . 2.

______________________ ^ ^6° ■ « 5 7 - ^ Blvd S u b s c r i p t i o n | U-SX , $3 per annum, including postage.

V o l . X L 1 X . L O N D O N , J U L Y , 1 9 3 3 . ____________ o n e^ hTl l in g

C O N T E N T S

PAGE

E d i t o r i a l p a g e Tr 0 5

^ , • V a n c o u v e r ...

° e S ... 2 Bridge River ; Lillooet; Cariboo; Nelson; Coast.

Government Delegates to tte International Geological 0-7

Congress; Kavirondo Goldfields; Roval . . . . 0/

Polytechnic Society’s Centenary Celebrations ■tk l o r o n t o ...

American Debt; T h e ’’Plastic’’ Age; British Non- Gold Production of Ontario; Porcupine; Kirkland Ferrous Metals Research Association. Lake ■ Sudbury ■ Quebec; Manitoba; North-

R a n d T a x a t i o n 2 Western Ontario. ’

The effects of the taxation proposals affecting the gold PERSONAL ^ ^

mining industry in the Union budget are examined.

G e o p h y s i c s i n t h e O i l f i e l d ... 4 T r a d e P a r a g r a p h s ... 40 A recent account of progress in geophysical survej ing is C o n rad D D 2 C om bination R i g ... 40

reviewed.

T h e R o y a l S c h o o l o f M in e s D i n n e r . . . 5 M e t a l M a r k e t s ... 41 An account of proceedings at this annual function.

St a t i s t i c s o f Pr o d u c t i o n ...

R e v i e w o f M i n i n g ... 6 pR IC E S Qp C h e m i c a l s ... 4 5

Ar t i c l e s Sh a r e Qu o t a t i o n s ... 46

T h e R o a n A n t e l o p e C o n c e n t r a t o r

/ . W . L i t tl e fo r d 9 M i n i n g D i g e s t

A description of the concentrator and an account of T he S co ttish A lum inium I n d u s try

results obtained. ' George B oex 47

S e k e n k e G o l d M in e , T a n g a n y i k a D riv in g in B roken G round . . . E . B Dow 51 T e r r i t o r y ... J o h n P . B o l t 19 T h e B oise-R ochester Mine, A tla n ta , Id a h o

The author describes the largest gold producer in East Stewart Campbell 53

Africa, a mine originally worked by the Germans

but now owned by the Tanganyika Central Gold T re a tm e n t of A sbestos . . W . A . R u K e y se r 5b

Mines, Ltd. S ep aratio n T echnique in th e C hem ical

G o ld i n B r i t i s h C o l u m b i a _ i n d u s t r y ... 59 H . G. N ic h o U s 23 F ioata b ility of Gold

A review of the on q 0 ld n g ht and R. E . H ead 60

calculations as

Province. SHORT N O T IC E S ... 61 E a r t h M o v e m e n t s . . . .C . P . S t r o m e y e r 2 /

A theory of RECEN T PA TENTS PUBLISHED ... 61

particul-.r N E W BOOKS, PAMPHLETS, ETC... 6 2

Ne w s Le t t e r s 3 0 ^ , ,

J o h a n n e s h ^ g ; ; . - ^ ; ; ^ ’R e n t's ';'mot; Co m p a n y Re p o r t s ... 62 East Rand L h f SonthWef 1 Randfontem Estates; J a n « » Tin; Biskhi Tin ; Chosen Corporation; East Pool Drills in viei; Southern Rhodesia , M?adle and Agar; Great Boulder Proprietary; Ipoh Tin • Kazera Luipaards Company ; Rezende Mines ; (Uganda) Tinfields ; Lahat Mines ; Siamis4 Tin ■ Sons of Gwaha

\Vilwatersr„ CoHieries ; Swaziland Concessions. South Kalgurh ; Southern Tronoh ; Taquah and Abosso ; Tavoy VereeniS10" g g 1 in Dredging; Transvaal Gold Mining Estates; Tronoh Mines. "

B r i s b rt” e ?Pent' GoldTn thi°Northerrr Territory i D IV ID EN D S D E C L A R E D ... 64 dooJ^A N-I- ; Mount Lyell ; New Caledonia XT ~

S e a G°ld’ Ne w Co m p a n i e s Re g i s t e r e d... 64

NicheI- !

1 - 2

E D IT O R IA L

A T th e In tern atio n al Geological Congress, which is tak in g place a t W ashington from Ju ly 22 to Ju ly 29, th e B ritish G overn­

m ent delegates are Sir Jo h n F le tt, Professors C. G. Cullis and O. T. Jones, Mr. W. Campbell Sm ith, and Dr. K. S. Sandford.

T WO new areas in th e K avirondo gold- fields (Nos. 3 and 4 of Sir A lbert K itson’s report) have been declared open. T hey have been divided into 57 p a rts and applications are invited for exclusive prospecting licences covering a period of one year. A provisional geological m ap of the K akam ega field has recently been issued by th e Mining and Geological D epartm ent, Nairobi.

T H E centenary celebrations of th e R oyal Cornwall Polytechnic Society are being held in F alm outh, Camborne, an d Penzance from J u ly 18 to Ju ly 21. The arrangem ents include visits to St. M ichael’s M ount and the works of Messrs. H olm an B rothers and Messrs. Bickford Sm ith and Co. and lectures by Sir R ichard Gregory, Sir Jo h n Cadm an, Sir N apier Shaw, and Professor S. J.

T ruscott.

S PE A K IN G last m onth in th e H ouse of Commons Mr. R. K. Law, explaining th e position of his father in connexion w ith th e American D ebt settlem ent, said : “ Mr.

Bonar Law held th a t th is was n o t an ordinary contract in th e spirit, w hatever it was in th e letter. He held, in his own words, th a t you could not m easure blood against m oney.” This, it will be rem em bered, was th e view expressed in th e

in Ja n u a ry last.

A CCORDING to one a u th o rity the iron age, in which it is generally conceded we are now living, is shortly to be succeeded by th e plastic age. However ex trav ag an t th is statem en t m ay sound— and it was delivered in all seriousness to the Society of Chemical In d u stry last m onth—there is no denying th e fact th a t th e synthetic resins are finding increased uses in every­

day life, to th e displacem ent of such ornam ental m etals as copper, bronze, nickel, an d others of their kind. The plastic m aterials have properties which render th em serious rivals to the common m etals and alloys.

T hey have high tensile an d com pressive strength, are light in w eight, have low h eat and electrical conductivity, an d are fire­

proof, while th e y can be read ily m oulded into any shape and in alm ost a n y colour or m ixture of colours. T heir life, how ever, still rem ains to be proved.

M IN IN G m en m u st of necessity be interested in th e activ ities of concerns such as th e B ritish N on-F errous M etals Research Association, since th e ir w ork results in extended uses being found for base m etals. The association’s re p o rt—

the th irte e n th —ju st published records th e continuation of valuable w ork done in the solution of problem s presented to it by th e consuming industries, w hich form th e bulk of its m em bership. A well-deserved trib u te is paid to D r. R. S. H u tto n , th e association’s director alm ost since its inception, who resigned in S eptem ber last on his appointm ent to th e first G oldsm ith’s Professorship of M etallurgy a t Cam bridge U niversity. He was succeeded b y D r. H . Moore, who was form erly D irector of M etal­

lurgical Research a t Woolwich Arsenal.

T hus th e bond betw een th is essentially commercial and industrial organization and G overnm ent-sponsored research is still fu rth er strengthened. A nother p o in t of interest is th a t th e In tern atio n al Tin Research and D evelopm ent Council has concluded negotiations for co-operation w ith th e association.

Rand T axation

In th e

for F eb ru ary last th e position of th e R an d gold-producing in d u stry w ith respect to th e situation created by th e departure of th e Union from th e gold s ta n ­ dard was reviewed in th e light of a speech m ade by Mr. Jo h n M artin, president of the T ransvaal Chamber of Mines. Mr. M artin was th en confident th a t under th e different conditions som ething in th e n a tu re of a new m ining policy would be evolved, in p u rsu it of which full advantage w ould be ta k e n to lower p ay lim its, to increase ore reserves, and to accelerate th e developm ent of b o th old and new areas. In A pril— after three m o n th s’ w ork under prem ium conditions—

th e progress m ade in th e direction of

forwarding this new policy was exam ined

and it was pointed out th a t th ree m ajor

elem ents of u n c ertain ty m ust be carefully considered before any prophecy as to th e fu tu re of th e R and gold m ines could be m ade.

These elem ents were : The wages question, u n c e rta in ty as to th e n atu re of subsequent tax atio n , and d oubts as to th e future of gold. As to th e th ird of these factors, the position, broadly speaking, rem ains the same, th e general concensus of opinion being th a t th ere is noth in g to replace gold as a satisfacto ry sta n d a rd for international exchange purposes. Of th e first— th e wages question—th is is still ra th e r obscure and is referred to later. The ta x a tio n question, how ever, has to a certain e x te n t been cleared u p b y th e provisions m ade in th e South A frican budget su b m itted to th e newly- elected U nion P arliam ent last m onth and it is th is which justifies a re tu rn to the subject.

Before th e introduction of th e Union b ud g et there h ad been m any surmises as to th e proportion of th e gold prem ium th a t would be tak en by th e new adm inistration, certain sections of th e local Press prophesying th a t 50% w ould be th e am ount claimed, a conjecture th a t m ost people th o u g h t to be exaggerated. As it happened, th is figure was very near th e m ark, for Mr. H avenga, th e Finance M inister, announced his in tention of raising an a dditional £6,000,000 from the in d u stry , an in ten tio n th a t was resented by th e m ining in d u stry and the Reef population.

The storm of criticism aroused by th e new m easure has resulted in certain am endm ents being m ade to th e original proposal, which was set out as a scheme for im posing an excess-profits d u ty on th e additional revenue derived by th e m ines from th e prem ium . The exact wording of th e m easure has been generally a d m itte d to be obscure, b u t the in ten tio n of th e Union G overnm ent is perfectly plain. T hey desire to separate the prem ium benefit from ordinary tax atio n , th e m axim um d u ty to be levied now being fixed a t 70% of th e excess, n o t 80% as a t first proposed. Mr. H avenga himself was obliged to leave South A frica for London, to a tte n d th e W orld Economic Conference, an d th e handling of th e m easure in th e Union P arliam en t was left to Mr. P a tric k D uncan, M inister for Mines. Mr. D uncan em phasized Mr. H av en g a’s determ ination to ta k e 50%

of th e prem ium and g u aran teed th a t th e additional ta x a tio n in 1934-35 w ould not exceed £7,400,000, which would be about 57% of th e gold prem ium . The m a tte r is now settled, having been passed by th e Union

P arliam ent, and it only rem ains to exam ine its effect on th e gold in d u stry of th e Union.

I t is interesting to note th a t th e South A frican M ine-W orkers’ U nion has declared itself to be entirely satisfied th a t th e new revised ta x a tio n is fair and reasonable, so th a t some good m ay have arisen from it here, since if th e Governm ent is tak in g a large lum p of th e prem ium th e w orkers are n o t likely to claim it. In o th er words, th e wages question can hard ly become as acute as at one tim e appeared probable. The G overn­

m e n t’s contention th a t th e prem ium is

“ an increm ent due solely to S tate action ” m ust be ad m itted, as also its view th a t " the continued existence of th e prem ium is u n ce rtain ,” and it is impossible not to recognize th a t th ere is still a prem ium even if it is only h alf w hat was a t first th o u g h t to be coming to th e industry. Thus there are still th e m eans available for th e working of ore below th e previously accepted lim its of payability, although it appears to be here th a t th e critic m ay w ith some fairness charge th e Union G overnm ent w ith short-sighted­

ness. I t m ight have recognized th a t a certain length of tim e m ust necessarily elapse before low-grade reserves can be sufficiently developed to mine—th a t is, before th e full effects of th e in d u stry ’s declared “ new policy ’ ’ could become ap p aren t— and th a t th e lim it of p ayability cannot be lowered as m uch as it would have been h a d th e new ta x a tio n not been so heavy. I t is, perhaps, too early to judge of th e final effects of the new m easure, especially as th e official exam ples of calculated taxes are so obscurely set out as to m ake it appear th a t lower- grade m ines m ay feel the ta x more th a n those w orking high-grade m aterial. W hether th e U nion Governm ent will benefit in th e long ru n by its action rem ains to be seen, while it seems to some inequitable th a t th e mining in d u stry should be tax ed to help th e farm ing com m unity, since th e agriculturist m ust benefit as m uch as anyone from the depreciation of the South African pound.

There is, too, th e fact th a t th e gold in d u stry in Southern Rhodesia and other p arts of th e E m pire has n o t been penalized so severely. One certain effect m ay be recorded an d th a t is th a t various schemes for the resuscitation of old areas an d th e develop­

m ent of new ones have, tem porarily a t any rate, been shelved and, although th ere is a tem p ta tio n to suspect th a t b o th th e G overn­

m ent and th e in d u stry have been striving

afte r 60% of th e prem ium , such an effect

4

is m uch to be deplored. Once again we m ight say th a t th e extension of th e life of the in d u stry should be th e m ain end in view, not increased ta x a tio n and dividends, and it seems likely th a t th e Governm ent m ay find it wise to accord— in Mr. H avenga’s own words— “ special tre a tm e n t to new developm ent on th e lines of legislation already in force in respect of Governm ent leased areas.”

G eop h ysics in th e O ilfield

The fact th a t, as recorded elsewhere in this issue, th e W orld Petroleum Congress is m eeting in London during the present m onth m akes it singularly appropriate to refer to a review of recent progress in geophysical exploration as applied to oilfield w ork th a t has been m ade by Mr. Oscar W eiss.1 I t is, perhaps, n o t generally realized th a t a m odern oilfield organization will include specially-trained m en capable of exploring buried stru ctu res by geo­

physical m ethods or th a t their m ethods have become so firmly established th a t th e future is likely to witness considerable expansion.

In m any fields alm ost all th e surface geology has been roughly explored and th e well records correlated and in such cases any additional inform ation th a t m ay become available as th e result of surveys by geophysical m ethods will be eagerly seized upon by th e geologists in charge. As the au th o r of this review points out, much experience was w asted in th e days of early geophysical w ork by the failure of the geophysicist to realize or a t any ra te adm it th e great ex ten t to which he is indebted to th e geologist for his inform ation. Nowadays, however, geophysical exploration, like aerial reconnaissance, is recognized to be a new and useful tool in helping in the unravelm ent of a geological stru ctu re and, although the final m athem atical considerations involved in the study of anom alous observations m ust rem ain in th e hands of the train ed specialist, sufficient has been m ade available in the w ay of graphical checks to enable the geologist concerned to be able to confirm or control th e w ork of his colleague.

As far as geophysical instrum ents are concerned, th e developm ents of recent years have been confined m ainly to th e modifica­

tion of types already well known. Mr. Weiss adm its th a t no new m ethods have been p u t

1 J o u rn a l of th e I n s titu tio n of P e tro le u m T e c h ­ nologists. J u n e , 1933.

in practice, although th e cost of deep drilling and th e urgent need for m ore precise d a ta relating to deeper horizons has m ade more and more exacting dem ands on those m ethods already firm ly established. These new requirem ents have been m et in th e m ain b y increasing th e sensitivity of in stru m en ts concurrently w ith an increase in m echanical robustness to enable th em to w ith sta n d th e rigour of field work, while th e accuracy of m easurem ents an d th e ir reliable in te r­

p re ta tio n have been g reatly enhanced by combining results o btained by different m ethods. I t is recorded th a t certain areas in the Gulf Coast of Texas a n d L ouisiana have been twice surveyed by th e torsion balance and four tim es by seism ograph, in each case im provem ents in th e in stru ­ m ents a n d m ethods of calculation having disclosed th e lim itations of th e work previously done. This th e n is th e n a tu re of th e progress in recent years—th e develop­

m ent of higher accuracy an d th e com bina­

tion of different m ethods.

T urning to th e advances recorded in the use of th e various m ethods, th e a u th o r states th a t under favourable conditions th e torsion balance is alm ost indispensable for obtaining reliable d a ta about hidden underground structure, th e precise th eo ry on w hich th e m ethod is based and th e m ass of accum ulated d a ta th a t has been checked b y drilling rendering it extrem ely valuable under certain conditions. In seismic w ork a g reat advance was m ade when seismic reflection was in tro ­ duced into oil prospecting, although th e m ethod can only be used w hen a reflecting surface exists and has been reliably identified.

U nder these conditions th e am o u n t of explosive required can be considerably reduced and very accurate d ep th d eterm in a­

tions m ade w ith either electrical or m echanical seismographs set up on th e surface or buried in holes. F o r oil w ork recent developm ents in ea rth m agnetic m ethods are not considered to have opened up any new possibilities, th e d e p th an d shape being generally indeterm inable by m agnetic prospecting, and th e a u th o r is of th e opinion th a t this m ethod is m ore likely to lose th a n gain im portance in course of tim e. The application of electrical m ethods to th e solution of oil problem s is a com paratively recent developm ent. T heory for th is ty p e of work has always been based on th e assum p­

tio n th a t th e m edia stu d ied w ould be

isotropic, b u t th e discovery of th e anistro p y

of stratified deposits has done m uch to

JU L Y , 1933 5 clarify th e position, p articu larly since the

com plications aroused by th e discovery have been overcome b y th e use of low-frequency currents. So m uch for surface work, b u t an interesting developm ent has been the advance m ade in m easuring th e resistivities of different beds by lowering electrodes in wells, a m ethod th a t has been frequently used for obtaining correlation d a ta . R adio­

active m ethods have n o t developed well and th e au th o r still aw aits th e process which will be capable definitely of locating oil directly.

I t is notew orthy th a t he does n o t th in k th a t such an advance is an im possibility. A developm ent of th is kind, of course, would not be confined to th e direct location of oil alone and, although its discovery is not likely to be m ade in th e im m ediate future, it is possible to agree w ith th e a u th o r th a t, in any case, geophysical exploration m ethods are likely to find increasing application.

The R oyal Sch ool o f M ines D in n er

The 56th annual dinner of the Royal School of Mines held last m onth under th e auspices of th e Old S tu d e n ts’ Association continued a series of functions well calculated to preserve an interest in th e School for its alum ni. As usual th e atm osphere was th a t of a family gathering, th e guests having been chosen from men know n to be sym pathetic to the aspirations of Mines m en and th e traditions of th e School ra th e r th a n from those well known in public life, who can only be indirectly interested in its fortunes. Among these friends of th e School— as th ey were very appropriately term ed later in the evening by Professor J. G. Lawn—m ight be m entioned Sir A lbert K itson, Mr. Justice Howes (from the Gold Coast), Mr. Leonard H olm an, and Mr. S. L. Bensusan, while the chair was occupied by Mr. A rth u r J. Ben­

susan, who was a t th e School from 1889 to 1894.

The to ast of “ The Royal School of Mines ” was in the able hands of Sir Albert Kitson, who, speaking as an A ustralian, expressed an envy of th e position th a t R.S.M. m en held in all p a rts of th e world. He tho u g h t of them as pioneers in th e tru e sense, m en who had gone to th e ends of th e earth in tim es of peace and yet who had not hesitated to offer their services in tim es of war. He felt th a t such m en m ust have h a d unparalleled experiences and he only wished more of th em would follow th e exam ple of Mr. E . T. M cCarthy an d pass on th eir knowledge to others by

more frequent publication. This, as our readers know, is a m a tte r on which the

has often had occasion to speak feelingly. I t has always felt th a t men should w rite more ; there is always someone to whom th eir endeavours will prove of use.

In reply Mr. A. J . Bensusan spoke of the trepidation he h ad felt in taking office for th e year and expressed his appreciation of th e efficient w ay in which th e affairs of the Association were m anaged by their able secretary, Professor T ruscott. He spoke of th e difficulties likely to confront a graduate leaving th e School a t th e present tim e, going on to discuss th e organization a t South K ensington and th e facilities th a t were available there, in spite of its not being situated, as, apparently, certain people would like it to be, in th e centre of a mining field. Referring to th e correspondence th a t appeared a year or so ago in these columns concerning th e education of th e mining engineer, Mr. Bensusan felt th a t he could do little b etter th a n quote another old Mines man, a t present in America, who once said th a t perhaps not so m uch depended on the wisdom of th e teacher as on th e virility of th e tau g h t, and considered th a t th e best possible m aterial should be available for the profession, as com petition was likely to become increasingly great. Mr. Bensusan concluded by announcing th a t Professor H enry Louis, who h ad recently been m ade a Fellow of th e Im perial College, would be the next occupant of th e presidential chair.

The to ast of th e guests was proposed by Professor Lawn, who, in th e course of an entertaining dissertation on th e etymological derivation of the words “ h o s t ” and

“ g u est,” arrived a t th e happy conclusion th a t th e la tte r word could, quite legitim ately, be interpreted as “ frie n d ” and thereafter consistently referred to th e official guests as friends. Professor Lawn subsequently m entioned th e individual services done to mining by the guests, not only those present, but those who had been unable to atten d . Mr. Justice Howes, in response, spoke of his com parative ignorance of m ining term s and customs, b u t showed his knowledge of the im p o rtan t m a tte r of concession titles and of th e m anner in which these m ight have been obtained on th e W est Coast of Africa.

The form al business of th e evening was

term in ated by th e to ast of th e Chairm an,

pleasantly proposed by Professor T ruscott,

who gracefully alluded to Mr. B ensusan’s

close fam ily connexion w ith th e School.

R E V IE W O F M INING

In trod u ction .—The lack of progress m ade

a t th e W orld Economic Conference, due principally to the desire of th e U nited S tates adm inistration to place its policy of price- raising before th a t of th e gold-standard countries for m onetary stabilization, appears to have h ad b u t little effect on business generally, th e position of gold as a stan d ard of value n o t having been assailed. A lthough the hoped-for revival is n o t y et a t hand, therefore, there appears to be a growing confidence in the future and m etal prices, a t an y rate, have continued steadily to advance, while th ere has been a fu rth er m arked im provem ent in th e em ploym ent figures.

T ran svaal.—The o u tp u t of gold on the

R and for Ju n e was 868,834 oz. and in outside districts 49,799 oz., m aking a to ta l of 918,633 oz., as com pared w ith 944,604 oz.

in May. The num ber of natives em ployed in th e gold mines a t the end of June totalled 229,751, as com pared w ith 227,178 a t the end of May.

The accom panying table gives th e dividends declared by the R and gold-mining companies on account of the p ast half-year.

Figures for th e preceding three half-years are given for com parison, b u t it has to be rem em bered th a t w ith th e exception of the V an R yn p ay m en t those for the second half of 1932 were paid in South African currency a t th e rate ruling on Ja n u a ry 27 last, while

2nd 1st 2nd 1st

half, half, • half, 1932.

half.

1931. 1932. 1933.

s. d. s. d. s. d. s. d.

Brakpan ... 4 0 3 0 4 0 4 6

Consolidated Main R e e f.. 1 3 1 3 1 3 1 6

Crown ... 3 6 3 6 4 3 6 3

D ag g afo n tein ... — 1 6

Durban Roodepoort Deep 0 9 0 9 0 9 1 9

East G e d u ld ... 1 0 1 9 3 3 East R a n d ... 0 6 0 3 0 3 0 9 G e d u ld ... 3 6 3 6 4 0 5 3

Geldenhuis Deep ... 1 0 1 0 1 0 2 6

Government A r e a s ... 2 3 2 3 2 3 3 0

Langlaagte Estate ... 2 0 2 0 2 0 2 6

Luipaards V lei... ^— 0 3

Modderfontein B ... 1 6 1 3 1 3 1 3

Modderfontein D eep. . . . 3 0 2 9 2 9 3 0

Modderfontein East . . . . 2 0 2 0 2 0 2 6

New Modderfontein . . . . 5 0 5 3 5 0 5 3

New State Areas ... 2 0 2 0 2 3 2 6

Nourse Mines ... 0 9 0 9 0 9 2 0

Randfontein... 0 6 0 9 1 0 1 0

Robinson Deep (A Is.) . 1 6 1 6 1 6 1 6

Robinson Deep (B )... 0 6 0 6 0 n 1 6

Rose D e e p ... 0 6 — 0 6

Simmer and J a c k ... 0 2 — 0 n 0 5

Springs Mines... 4 (1 3 9 3 9 4 6 Sub N ig e l... 3 6 4 0 4 0 6 6 Van R y n ... 0 9 1 0* 1 0* 2 0*

Van Ryn D eep... 2 6 2 0 2 0 2 0

West R a n d ... 0 3 0 a 0 6 West S p rin g s ... 0 9 0 9 0 9 1 0

W itwatersrand Deep . . . . ^{— —} 2 0

W itw atersrand Gold . . . 0 6 0 3 0 3 2 0

* F r e e o f t a x .

6

the la te st d istrib u tio n s show th e effect of th e gold prem ium . I t will be seen th a t D aggafontein Mines has joined th e list, while W itw atersran d D eep retu rn s. A s ta te ­ m ent has been issued b y th e L uipaards Vlei com pany statin g its in te n tio n to follow th e practice adopted last y ear an d to declare a final dividend in respect of its financial year, w hich ended on Ju n e 30.

L ate st advice w ith respect to th e boring being u n d ertak en on th e W est W itw aters­

ran d A reas properties is to th e effect th a t a reef has been intersected in th e V enterspost bore-hole No. 11, w hich was down 3,381 ft.

on Ju n e 23 last.

The P otchefstroom tow n council has accepted the tender of th e Anglo Am erican Corporation for gold prospecting rig h ts in Potchefstroom tow n lands, w hich cover about 10,000 m orgen ad jacen t to th e town.

Shareholders of P o tg ietersru st P latinum s have been inform ed th a t operations are to be re sta rte d a t an early d ate b y R u sten b u rg P latin u m Mines, L td.

The accounts of H enderson’s T ransvaal E sta te s for th e year to M arch 31 last show a profit of £35,100, increasing th e sum brought in to £65,703. A dividend paid during th e year absorbed £10,564, equal to 2£% , an d a fte r m aking o th er allowances th ere was an available to ta l of £52,752.

A final dividend of 2 |% for th e y ear leaves

£42,188 to be carried forward, from w hich an interim pay m en t of a sim ilar a m ount has been declared for th e c u rre n t year.

D uring th e period from its incorporation in December, 1931, to th e end of 1932 th e H .E . P roprietary, L td ., m ade a profit of

£29,752, from w hich a dividend equal to

and leaving £7,252 to be carried forw ard.

S ou th ern R h od esia.—T he

o u tp u t of gold from S outhern R hodesia during M ay was 53,358 oz., as com pared w ith 53,559 oz.

for the previous m o n th and 46,854 oz. for May, 1932. O ther o u tp u ts for M ay were : Silver, 8,721 oz. ; coal, 45,806 tons ; chrom e ore, 3,868 tons ; asbestos, 3,700 tons ; iron pyrites, 815 tons.

The contract recording th e purchase of the m ineral rights of Southern R hodesia by the G overnm ent was signed last m o n th and the purchase price of £2,000,000 paid over. The C hartered com pany has decided to pay an interim dividend of 6d. per share in respect of th e current year.

N orth ern R h od esia.— A re p o rt of th e

R hokana C orporation covering th e half-year

JU L Y , 1933 to Ju n e 30 sta tes th a t blister production totalled 26,038 tons, the to tal cost per long ton being ¿21-584, including debenture interest. I t has been decided to erect an electrolytic refinery a t N ’K ana, having a capacity of 36,500 short tons per annum , and it is hoped to s ta rt production ab o u t the m iddle of 1934. A rrangem ents have been m ade for th e production of b o th cobalt alloy and electrolytic cobalt.

The accounts of the R hodesia Broken Hill D evelopm ent Com pany for 1932 show a credit balance of ¿23,169, as com pared w ith a debit of ¿41,627 for th e previous year. A fter deducting th e d ebit of ¿17,927 brought in and m aking other allowances there was a credit of ¿7,668 to be carried forward.

I t is sta te d th a t the o u tp u ts of zinc for 1933 and 1934, estim ated a t 18,500 tons and 20,000 tons respectively, have been sold.

A circular to shareholders of the N orth C harterland E xploration Com pany issued this m onth states th a t an agreem ent has been concluded w ith Loangwa Concessions, L td., granting th a t com pany exclusive prospecting rights over the concession in th e Sasare district.

G old C oast.—A t

an ex trao rd in ary m eeting of th e K w ahu Mining Co. (1925), L td ., held this m onth, an increase of capital to ¿40,000, by th e creation of 100,000 new 2s. shares, was approved and these shares are to be offered to existing holders a t a price of 5s. per share. The com pany has an offer for floating th e T uappin and Bondaye properties under consideration.

The registration of Konongo Gold Mines was announced in the

last m onth.

T his com pany has acquired the pro p erty held by L y n d h u rst Deep Level (Gold and Silver) and preparations for opening up are in hand.

N i g e r i a . — E x-L ands

Nigeria, L td., proposes to capitalize ¿19,986 4s. of its reserve fund and to issue the 199,862 new 2s. shares as a bonus to existing holders in th e proportion of one share to every nine held.

K enya.— Shareholders of th e T anam i Gold

Mining Syndicate have been inform ed th a t after an exam ination b y Messrs. Bewick, Moreing, and Co. an option has been acquired on th e claims of th e R osterm an Mining Syndicate, a t K akam ega.

I t was announced last m onth th a t a con­

cession in th e K akam ega field had been acquired b y L y n d h u rst Deep Level (Gold and Silver), L td.

B elg ia n C ongo.—The accounts of the

Union Minière du H a u t-K a ta n g a for 1932 show a gross profit of 39,309,713 francs.

A fter adding the balance brought in and m aking other allowances th ere was an available to ta l of 156,672,696 francs, which has been applied to the redem ption of immobilized capital and other purposes.

A u s tr a lia .—D uring 1932 the operations

of the Zinc C orporation resulted in a profit of ¿94,838. A fter adding ¿56,887 appro­

p ria ted for new p lan t (unexpended) and the sum brought in, there was an available to tal of ¿188,088. Of this am ount dividends absorbed ¿71,609 and developm ent and new p lan t ¿70,000, leaving

¿46,479 to be carried forward. The ore tre a te d during th e year am ounted to 350,000 tons, b u t developm ent has been such th a t no reduction is shown in th e ore reserves, which a t th e end of the year am ounted to 2,800,000 tons on the "lead lode and 249,000 tons on the zinc lode.

A t ex trao rd in ary m eetings of the debenture holders of M ount Isa Mines, L td., and of Mining T ru st, L td., held this m onth, th e sale of M ount Isa Mines, L td ., to an operating com pany of the same title in Queensland was approved. The Mining T rust, L td., and th e Am erican Sm elting and Refining Co. have expressed th eir willingness to defer redem ption of their debenture holding for five years and, while th e redem ption of the rem aining debentures will be carried out according to th e original plan, holders would be given th e o p p o rtu n ity of deferring repay­

m ent for five years.

At th e general m eeting of G reat Boulder P roprietary, held last m onth, a resolution increasing the capital to ¿250,000 b y the creation of 750,000 new 2s. shares was approved. These shares are to be offered to shareholders a t 5s. per share and th e proceeds will be utilized for the erection of a new plant for the tre a tm e n t of sulphide ores.

An ex trao rd in ary m eeting of South K algurli will be held following th e general m eeting this m onth, when it wifi be proposed th a t the capital be reduced b y th e repaym ent of 2s. 6d. on each 7s. 6d. share. If th is is approved it will be proposed th a t 200,000 new 5s. shares will be created to increase the capital once again to ¿150,000.

New Z ealand.—The accounts of Con­

solidated Gold Fields of New Zealand for 1932 show a profit of ¿16,833, increasing the sum brought in to ¿30,217, of which

¿15,625 has been d istrib u ted as dividends,

T H E M IN IN G M AGAZINE equal to Is. 3d. per share, leaving £14,592

to be carried forward. The rep o rt for 1932 of B lackw ater Mines, L td ., in w hich th e com pany is largely interested, shows a profit of £35,756, giving, w ith the sum brought in, an available to ta l of £45,749. Of this am ount £31,249 has been paid as dividends, equal to 2s. 6d. per share, leaving £14,500 to be carried forward. B lackw ater Mines tre a te d 41,402 tons of ore, recovering gold w orth £133,852. The ore reserves a t the end of th e year were estim ated to be 75,435 tons, averaging 9-64 dw t.

In d ia.—D uring 1932 the Indian Copper

Corporation m ade a profit of £14,517, after placing £22,500 to depreciation reserve,

£1,100 to debenture redem ption reserve, and allowing for expenses on the issue of debentures. W ith the sum brought in there was an available profit of £20,527, which was carried forward. The com pany treate d 185,894 tons of ore during th e year, the refinery o u tp u t totalling 4,443 tons of refined copper, while 5,440 tons of yellow m etal sheet was produced a t th e rolling mill. A t th e end of the year th e ore reserves were estim ated to be 700,466 short tons, averaging 3-05% copper.

B u rm a .—A t an ex trao rd in ary m eeting of

Mawchi Mines, L td ., held th is m onth, an arrangem ent w ith option holders to subscribe in cash for 240,000 shares a t 4s. per share and to cancel th e option on the rem aining 200.000 shares in re tu rn for a bonus of 50.000 shares was approved. This arrange­

m ent will provide £48,000 working capital for developm ent work.

K orea.— I t was announced last m onth th a t

control of th e Chosen Corporation had been acquired by a French Syndicate.

N e w fo u n d la n d .— Shareholders in the

Anglo-Newfoundland Developm ent Com­

pany have been inform ed of arrangem ents concluded w ith the B uchans Mining Com pany for prospecting 1,280 square miles of the c o u n try owned by T erra N ova Properties.

V enezuela.—A circular to shareholders

of New Goldfields of Venezuela, L td., states th a t w ith the tram w ay between the LTnion mine and the mill a t E l P eru in operation developm ent a t the P eru group will be accelerated. Mr. C. O. Lindberg, who has recently retu rn ed from a v isit to th e mines, reports th a t deeper exploration promises the discovery of ores sim ilar in tenor to those now developed below d a tu m level.

P a n a m a .—A developm ent report issued

b y th e P an am a C orporation (Canada) states th a t th e erection of a tre a tm e n t p lan t of

a capacity of 30-50 tons a d a y is proceeding rapidly a t th e M argaja mine and th a t production is expected to s ta rt in Novem ber.

Y ugoslavia.—An in terest in K apaonik

Mines, Novo B rdo Mines, and Zletovo Mines, controlled b y th e C anadian Selection Com­

pany, has been acquired b y th e C entral Mining and Union C orporation groups.

S p ain .—The rep o rt of th e E sp eran za

Copper and Sulphur Co. for 1932 shows a profit of £4,860. A fter allowing for incom e ta x and adding th e am ount b ro u g h t in,

£29,412 was carried forw ard. In Spain production was on a reduced scale, while operations in Cyprus were stopped early in the year.

C ornw all.—The rep o rt of South C rofty

for 1932 records a loss of £7,405, increasing th e deb it balance to £22,969. O perations were on a reduced scale, 55,338 tons being milled, producing 645 tons of black tin and 133 tons of arsenic.

A t an ex trao rd in ary m eeting of W heal R eeth Tin, held th is m onth, a proposal to w rite down th e value of th e shares from 5s.

to Is. and to restore th e cap ital of th e com ­ p an y to £90,000 b y th e creation of 1,040,000 new Is. shares was approved. This arrange­

m ent has in view the re-opening of the mine.

D erb ysh ire.— F o r th e year to M arch 31

last th e accounts of Mill Close Mines show a profit of £66,436. A fter m aking allowance for depreciation, a dividend distrib u tio n equal to 2s. 6d. per share, absorbing

£40,230, and adding th e sum brought in, th ere was an available sum of £64,375.

A final dividend of Is. per share has been paid. The mine has been w orking a t full capacity and arrangem ents have been m ade for th e re-equipm ent of th e W arren Carr sh aft w ith electrical w inding gear an d ore bins. The production of pig-lead from the works a t Lea con stitu ted a record, b u t difficulties w ith th e furnaces have m ade it advisable to erect new sm elting p lan t.

A n g lo -P ersia n O il.—The accounts of the

A nglo-Persian Oil Com pany for 1932 show a profit of £2,379,677, after m aking full provision for all royalties and ta x a tio n due to the Persian G overnm ent under the recent settlem ent. The dividend has been increased b y 21% to 7% .

T in.—The figures available a t th e end of

Ju n e show a reduction of th e “ visible

su p p lie s” am ounting to 2,070 tons, while

the carry-over in th e E a st declined b y 190

tons, m aking a to ta l reduction of 2,260 tons,

following th e decrease of over 1,000 tons in

May.

T H E ROAN A N T E L O PE CONCENTRATOR

By J. W. L 1TTLEFO R D

A descrip tio n of concentrating m ethods em ployed by R o an A n te lo p e C o p p e r M in es, L td ., an d an account of the results o b tain ed .

Several articles have appeared from tim e to tim e in th e m ining press concerning the various phases of th e developm ent of the R oan A ntelope mine an d th e general design of th e surface p lan t, th a t by A. G.

McGregor, appearing in th e

for Novem ber, 1930, will be recalled by your readers. The concentrator has now been in operation for nearly tw o years and th e following description of th e mill itself and the operating results obtained will doubtless be of general interest.

The ground plan (Fig. 1) indicates the location of th e several milling u n its in relation to th e B e a tty shaft, which is the m ain hoisting shaft a t present. I t will be noted th a t th e coarse a n d fine crushing departm ents are very closely connected to th e mill proper, m aking for very close co-operation, between these units. The skips from th e B e a tty shaft discharge directly into th e coarse ore bins a t the prim ary crushing p lant. The concentrate filtering plant, tailings thickening p lan t, and tailings dam are located 1,700 ft., 2,500 ft., and 3,500 ft. respectively in a south­

easterly direction from th e mill. In order to tak e advantage of cheap tra n sp o rt of concentrates by pum ping, th e filter plan t is located close to th e sm elter storage bins for flux an d charge and reverts. The tailings thickener was so placed as to obtain a gravity flow from th e mill an d still be adjacent to th e dam , th ereb y m aking use of only one pum ping operation to complete the disposal of tailings.

The ore-bearing series of th e R oan Antelope consist of d ark grey-green, grey, and som e­

tim es brownish m etam orphosed argillaceous shales an d sandstones. Sandy partings, stringers of quartz, orthoclase, pegm atite, and seams of calcite are often present. Shale is th e principal m ineral-bearing rock, while chalcocite, bornite, an d chalcopyrite are the chief copper m inerals present. The dis­

trib u tio n of these is variable. In the eastern zone (th a t which is now being mined) chalcocite is dom inant, whereas in the w estern area chalcopyrite and bornite predom inate. The chalcocite is finely dissem inated thro u g h o u t th e rock m ass and is rarely discernible w ith th e naked eye.

O utcrop oxidation continues down to the w ater table (100 ft. to 200 ft.). Below this level it still persists, but in diminishing quantities. The oxides are usually chrysacolla, m alachite, cuprite, and m elaconite, while native copper and sooty- black m anganese oxides (named in order of im portance) are also present. The average mill feed assays for the first year of operation are shown in Table 1. The high oxide

Ta b l e 1.

Total Oxide Si02 AI2O3 Fe S CaO MgO Res.

Cu. Cu.

3-65 0-48 55-82 17'27 2‘94 0'86 0'81 4’33 14‘32

content of th e present mill feed is th e result of th e m ining program m e, which calls for stoping th e upper (and hence more highly oxidized) levels first.

From th e standpoint of crushing and grind­

ing th e ore presents few problems. I t m ay be considered as m edium -soft, is easily crushed, and causes very little w ear on the crusher parts, owing to th e preponderance of shale, which is not abrasive. Classification is also simple w ith present practice and no difficulty is experienced in obtaining a 90%

m inus 200 mesh product w ith 28% solids.

A complete general flow-sheet giving all p ertin en t d a ta is shown in Fig. 2. I t will be observed from the plan and flow-sheet th a t, while following generally accepted practice, there are a num ber of notew orthy features.

S tartin g w ith th e coarse-crushing plant th e ore as received from th e mine has all passed 22-in. grizzlies, b u t, owing to the slabby n atu re of th e rock, individual pieces will a t tim es weigh 500 to 600 lbs. The two 6-chain Ross feeders furnish a very uniform feed and it is seldom necessary to resort to blasting to loosen th e rock th a t has arched over in th e bins. Very fine ore, high in m oisture, causes some trouble, b u t is easily loosened w ith a very small stream of high-pressure w ater.

These feeders are followed by tw o 60-in.

belt conveyors, which discharge on to two

10 ft. 4 in. by 5 ft. 8 in. 4%in. grizzlies. The

load here reaches a peak of 900 to 1,000 tons

per hour per belt, depending on th e size of the

feed. All rock th a t has passed the under­

10

ground grizzlies is handled w ithout fu rth er reduction. The life of these belts is short, due to large pieces of rock falling directly on to the belt rath er th a n to ordinary wear.

In spite of this, however, it is e stim ated th a t good quality belts will carry over 600,000 tons each. The cost of m aintenance, which includes th e cost of new belts, is less th a n 0-002d. per ton.

The original grizzlies have been altered to tak e care of w et ore, which is encountered periodically and form erly caused considerable delay. The changes included spreading the bars a t th e lower end, to leave a tapered opening betw een bars tow ard th is end, a n d m ounting the upper end of th e grizzly fram e on heavy coil springs. The lower end of th e frame is hinged. The im pact of heavy pieces of rock falling directly over these springs sets up sufficient vibration to clear th e grizzly in addition to reducing th e terrific shock on th e grizzly bars. I t is seldom necessary to shut off th e feed to clean the grizzlies, whereas w ith th e rigid ty p e w ith parallel bars this was done several tim es per hour.

The tw o 30-in. McCully gyratories, set to crush to 4 \ in., have an hourly capacity of 500 to 750 net tons each w ith an initial feed of 750 to 1,000 tons per hour, depending, of course, on th e size and character of th e ore.

Only one crusher is in operation a t a tim e, th e other being held in reserve. Large th in slabs of rock often escape th e action of th e crushers and are passed on to th e Symons p lant.

A 42-in. inclined conveyor, 380-ft. centres, takes th e combined crusher product and grizzly undersize to th e d istributing conveyor over the Symons bins. This la tte r conveyor is equipped w ith a sem i-autom atic trip p e r for th e distribution of ore to th e different sections of th e bin.

The cost of m aintenance in th e coarse crushing d ep artm en t has been practically nil, a p a rt from No. 1 belt renew als and changes th a t were m ade im m ediately after sta rtin g operations.

The p lant as a whole operates very efficiently. Two E uropeans an d three n ative helpers co n stitu te th e operating crew and account for approxim ately 6,000 to n s crushed per 8-hour shift, w ith am ple tim e for cleaning up, oiling, etc. Cost per to n coarse crushed averages O'03 shillings, d istrib u ted as shown in Table 2.

The flow-sheet of th e fine crushing p lan t is very simple. Ore is delivered from the coarse ore bins to th e five T ype 60 H um -m er

Ta b le 2

E u ro p e a n lab o u r . . 0-007 shillings p e r to n . N a tiv e lab o u r . . 0-003 ,, ,, »

P o w er . . , 0-015 ,, -

Stores, etc. . 0-005 ,, „ ••

T o ta l . . . 0-030 shillings p e r to n .

screens an d five 5 |- ft. Symons crushers by roll feeders an d 24-in. conveyors equipped w ith m agnetic head pulleys. The ra te of feed is regulated from th e Sym ons operating floor by rem ote control to th e roll feeders. The H um -m er screens are set a t an angle of 37° a n d are equipped w ith i-in . by • l |- i n . m esh wire cloth, w hich rem oves app ro x im ately 15% of th e original feed as undersize. Screens an d crushers are in open circuit.

The H um -m er screen undersize is of a very clayey n a tu re an d carries a large portion of th e m oisture in th e ore. I t was necessary to instal an auxiliary conveyor to transfer this m aterial to th e cross conveyor under the Symons crushers, as it was found th a t it would n o t ru n in a chute placed a t an angle. The m oisture contained in th e undersize is largely absorbed b y th e Symons product, m aking it easy to handle and y et practically free of dust.

The d u st cre ated in fine crushing is well handled b y th e d u st control system designed by Mr. Geo. E. L ynch an d ab ly described by him in th e D ecem ber, 1932, n u m b er of th e

No fu rth e r com m ent will be add ed here, a p a rt from th e fact th a t no difficulties w hatever have originated in th e system .

As in th e coarse crushing p lan t, th e w ear on th e crusher w earing p a rts has been v e ry light and no replacem ents have been required.

The indications are th a t cone a n d bowl liners will be good for over 800,000 to n s of initial feed to each of th e H um -m er screens, or 680,000 tons net.

All cast-iron chute-liners have been replaced w ith locally m ade g rid -ty p e liners, in which th e ore form s its own w earing surface by filling in th e spaces betw een th e grid bars.

Ta b le 3

% Weight Accumulative on each Mesh

10 48 100 200

1-5 in. 0-371 in. Mesh. Mesh. Mesh Mesh

1-8 57-9 84-0 89-1 90-2 8-7 '

Table 3 shows a ty p ical screen analysis

of mill feed. Sizing te sts on th is ore are

liable to be m isleading in th a t th e am ount of

oversize while appearing excessive is due

JU L Y , 1933 11

e

is IT .

01

is it

hi

u

ffi

i

»1

a

oi “

;k

ers v ill or

ei is,

"S

9

0 FF*+— 100 FT —f-230 FT—I Fig. 1.—GroundPlanoftheRoanAntelopeConcentrator.

12

to the fact th a t a great portion is in the shape of th in slabs.

Two E uropeans and nine natives are employed on shift w ork on this plant.

A crusher forem an, one repairm an, and four operators comprise th e entire coarse and fine crushing E uropean operating force.

The cost distribution of coarse and fine crushing and conveying up to th e mill bins is shown in Table 4.

Ta b l e 4

E u ro p ea n lab o u r . . 0 - 0 4 shillings p e r to n . N a tiv e lab o u r . . . 0-01 ,, „ ,,

P o w er . . . . 0-03 ,, ,, ,,

M aintenance a n d supplies . 0-02 ,, ,, ,, T o ta l . . . 0-10 shillings p e r ton.

The mill bin is of the caten ary ty p e w ith capacity of 6,000 tons, which is sufficient for 16 hours’ ru n w ith tw o mills per section in operation. Roll feeders driven through worm gear reducers and adjustable as to speed and chute opening deliver mill feed to a cross conveyor which discharges on to an inclined conveyor delivering into th e ball-mill scoop-box. The inclined conveyors are equipped w ith Merrick w eightom eters.

The feed can be held to very uniform rates and variations are seldom over 1%.

The original grinding circuit has undergone several changes, each, however, showing an im provem ent on th e original. The diagram m atic flow-sheets shown in Fig. 3 show th e original plan and th a t a t present in use. I t will be noted in Fig. 3 th a t a t first both prim ary and secondary grinding was employed. This proved very satisfactory from a tonnage standpoint and th e capacity was finally established a t 1,500 to 1,600 tons per day per section a t 86% m inus 200 mesh grinding. W ith this tonnage, however, the bowl com partm ents of th e classifier were easily overloaded, resulting in a large am ount of oversize in th e overflow. To correct this condition th e feed was introduced into the rake com partm ent through a m anifold header pipe, th e result being practically no load in the bowl. This allowed th e speed of th e bowl rakes to be reduced from 4 r.p.m . to 2 r.p.m . and th e degree of fineness of th e overflow increased from 86% m inus 200 mesh to 90% m inus 200 mesh. Some difficulty was experienced in balancing th e load betw een th e prim ary and secondary mills. I t was therefore decided to try out single-stage grinding, th e result of th is being a record tonnage of 1,100 tons per mill day under ideal con­

ditions and w ith a m onthly average of 1,000 tons per mill day under norm al conditions.

The tonnage per mill is m ore or less regulated by th e fineness of grinding, which is m ain tain ed a t 90% through 200 m esh.

Conversion of th e existing secondary m ills in to p rim ary mills is now u n d er w ay. To m ake th is change it is only necessary to instal a cross conveyor a t th e head end of th e present No. 9 feed conveyor an d to furnish a suitable splitter-chute to divide th e feed betw een th e tw o mills.

The first of th e 12-ft. 4-rake p rim ary classifiers are being divided a t th e centre to m ake tw o sep arate m achines. G rav ity flow is o btained from th e mill discharge to th e classifier an d from th e sand end of th e classifier to th e m ill scoop-box by sim ply lowering th e classifier 20 in. This a t th e same tim e does aw ay w ith th e original scoop lifter.

Section 5, rem odelled as outlined, has been in operation four m o n th s w ith an average of 1,986 dry to n s per 24 hours. N o other m ajor changes will be necessary to step th e tonnage up to 9,000 or 10,000 tons per day, which is v ery n early double th e original rating. The flexibility of sm aller u n its will be ap p aren t.

The indications are th a t steel consum ption will be considerably lowered b y o perating all mills as p rim ary units. W hile th is is n o t thoroughly established, it seems reasonable to expect th a t th e p rim ary slime in th e feed would have a “ lu b ric a tin g ” effect, w hich is n o t so w ith secondary m ills grinding classified sands. Figures to d a te show a to ta l steel consum ption of 0'951b. of steel p er to n ground m ade up of 0 80 lb. of balls an d 0 1 5 lb. of liner steel.

Increased tonnage from single-stage grinding can be a ttrib u te d to tw o factors, th e first being th e m eth o d of feeding th e bowl classifiers, which im m ediately showed a definite im provem ent in th e am ount of oversize carried in th e overflow, m aking it possible to increase th e tonnage w ith b e tte r classification. Secondly, th e sticky n a tu re of th e p rim ary slime furnishes th e m edium which causes a th ick coating of pulp to adhere to th e balls, which, of course, is ideal.

This condition is n o t easily affected by th e pulp density.

The m ill-site being practically flat, all re tu rn circuits are handled by W ilfley pum ps.

These pum ps are all in duplicate an d very few in terru p tio n s occur from pum p failures.

The original estim ated life of pum p w earing

JU L Y , 1933 13

TO SMELTER BINS

D.

6.

7.

8^. 9.

1 0. 1 1.

1 2.

13.

14.

15.

16.

17.

18.

19.

2 0.

2 1.

2 2^.

23.

2 4 .

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

1. B e a tty h e ad fra m e b in s—2,000 to n s cap a city . 35.

2. Tw o 6-chain R oss feeders— r.p .m .— 10-h.p.

m o to rs th ro u g h T exrope an d red u ctio n 36.

gear.

3. Tw o 60-in. b y 16-ft. conveyors— 37-5 ft. p e r 37.

m in u te — 5-h.p. m otors. 38.

4. T w o 6-ft. b y 10-ft. grizzlies— 4-in. to 3£-in. 39.

openings— hinged b o tto m end— coil springs

to p end. 40.

Tw o 30-in. su p erio r M cCully cru sh ers— 180-h.p.

m o to r d riv e th ro u g h 14 l£ -in . b y 1-in.

T exropes.

One 42-in. b e lt conveyor (No. 2) 380 ft. long w ith incline lift of 72 ft.— 125-h.p. m otor.

O ne 42-in. b e lt co n v ey o r (No. 3) 109 ft. long w ith a u to m a tic trav e llin g trip p er.

Sym ons sto rag e bins— 3,000 to n s cap acity . F iv e 48-in. d ru m feeders.

F iv e 24-in. b e lt conveyors (Nos. 4 A -E ) incline lift of 27 ft.— m agnetic h e a d pulleys.

F ive 4-in. b y 6-in. T y p e 60 H u m -m er screens—

V64 v ib ra to r— ¿ -'n - b y l j- i n . screen o p e n ­ ings a t 37°.

F iv e 5^-in. Sym ons cone crushers direct co n n ected to 150-h.p. m otors.

O ne 30-in. collecting conveyor a n d 30-in. cross conveyor for H u m -m er screen undersize.

O ne 42-in. b e lt conveyor (No. 5) 85 ft. long.

One 42-in. b e lt conveyor (No. 6) 273 ft. long—

incline lift of 75 ft.

One 42-in. b e lt conveyor (No. 7) 375 ft. long w ith a u to m a tic trav e llin g trip p e r.

F ine ore bins— c ap a city 6,000 to n s— 1,200 to n s p er u n it.

T h irty 18-in. roll feeders— 6 feeders p er u nit.

F iv e 20-in. b e lt conveyors (No. 8) 46 ft. long—

collecting from roll feeders.

F iv e 20-in. b e lt conveyors (No. 9) 60 'ft. long w ith incline lift of 17 ft.— w eig h to m eter on each.

T en No. 98 M arcy b all m ills d irec t connected to 400-h.p. syn. m otors.

T en 6-ft. b y 2 0-ft. D o rr circ u la tin g classifiers—

a lte re d from five 12-ft. b y 2 0-ft. classifiers.

F iftee n 6-in. W ilfley sa n d pu m p s. Two o p e ratin g — one spare, for each tw o mills.

T en D o rr q u a d ru p le x bowl classifiers 12 ft. by 32 in. w ith 18-in. bowls— 10- a n d 5-h.p.

m otors.

One 30-ft. D o rr th ic k e n er altered to 6 ft. in h e ig h t— to classify reg rin d pro d u cts.

T hree 8-in. W ilfley sand pum ps. H a n d lin g bowl class. Overflow to flotation.

One 4-ft. b y 12-ft. F ra se r a n d C halm ers ball m ill for regrinding.

One w eir-ty p e flo tatio n feed d istrib u to r.

F iv e 22-ft. m atless flo tatio n m achines—

p rim a ry cleaners.

F iv e 16-ft. m atless flo tatio n m a c h in e s -- secondary cleaners.

One 40-ft. m atless flo tatio n m achine for reg ro u n d products.

T hree 4-in. W ilfley sand pum ps.

T en 22-ft. m atless flo ta tio n m achines—

p rim a ry roughers.

T en 60-ft. m atless flo tatio n m achines—

secondary roughers.

Tw o 35-ft. b y 10-ft. D o rr co n cen trate th ick en ers. P rovision m ad e for by-passing.

Tw o 3-in. ty p e “ CA ” W ilfley p u m p s— 40-h.p.

m o to rs— 1,700 ft. to filter p lan t.

T h ree 8-ft. b y 8-ft. Oliver filters.

One 250-ft. D o rr tra c tio n th ick en er.

F o u r 6-in. W ilfley sand p u m p s— 125-h.p.

m otors.

T ailings dam .

Fi g. 2 .— Ge n e r a l Fl o w-Sh e e t o f t h e Ro a n An t e l o p e Co n c e n t r a t o r.