The Mining Magazine, Vol. 42, No. 6

1 He Mining Magazine

M anaging D irector and E d ito r : W . F . Wh i t e. A ssista n ts : St. J . R . C. Sh e p h e r d, A .R .S.M ., D .I.C ., F.G .S.;

F . Hi g h a m, A .R .S.M ., M .Sc., F.G .S.

P u b lis h e d on th e

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Vol. XL11. No. 6. L O N D O N , J U N E , 1930.

O N E S H IL L IN G^{PR IGF}

C O N T E N T S

PAGE

Ed it o r ia l

Notes ... 330

S kinner’s “ Oil an d P etro leu m Y ear B o o k ” ; Professor W . W . W a tts ’ R e tir e m e n t; E d u c atio n of the E ngineer ; A nnual D inners ; R eport on E th y l P e tr o l; S ilv er; W estern A u stralia a n d th e Gold Bonus ; Tin R estriction P ro g ress; F u rth e r Silicosis L e g islatio n ; B irth d a y H onours ; M inerals S eparation Segregation Process.

The Steam Shovel in N igeria ... 331

A pap e r before th e M ay m eetin g of th e I n s titu tio n is discussed.

The F u tu re of th e R an d ... 332

A plea b y S ir Sothern H olland for reduction of w orking costs is endorsed.

E m pire U n i t y ... 333

The possible effects on personnel an d eq uipm ent of foreign ca p ital in B ritish enterprises is exam ined. Re v ie w o f Min in g ... 334

Ar tic les

Observations on th e Geology and Mines of th e Belgian Congo

G. Vibert Douglas 337 The author, who is the Chief G eologist to the R io T in to Company, gives some notes taken d u rin g a recen t v isit to th e K atanga.

Selective F lo ta tio n on a Lead-Zinc- G raphite Ore ...E . G. W ilkins 349

The au th o r describes a series of tests carried o u t a t the Eagle Lead Mines, Trefriw , in o rd er to d eterm ine the best m ethod for the elim in atio n of graphite.

The E arth -R esistiv ity M ethod of E lectrical Prospecting

E . Lane aster-Jones 352 Book Re v ie w s B eyschlag’s “ G eologische K a r te d e r E rd e ” G u te n b erg ’s “ T h eo rie d e r E rd b eb e n w e lle n ; B e o b ac h tu n g e n ; B o d e n u n ru h e ” Capt. H . Shaw Let t e r s to t h e Ed ito r

The E ducation of th e Engineer

H. T . Tizard 357 Dr. C. Baring Horwood 357

Magnestie D eposits in Serbia

Dr. H. C. Boydell 358 New s Le t t e r s

Johannesburg ... 359

Gold O u tp u t Still In c re a sin g ; A Race to the R e e f ; W orld’s D eepest Mine ; T ran sv aal C o p p e r; A R hodesian Iro n Ore D e p o s it; D iam onds in Portuguese E a st Africa.

B r is b a n e ... 360

M ount Isa M in e s; N o rth Q ueensland M in in g ; The Coal S to p p a g e ; Coal C omm ission R e p o r t; A u stralian an d New G uinea O il P ro sp ectin g ; M ining in W estern A u s tra lia ; A m algam ated Zinc Company. 355

P erth ... 362

The Gold D iscovery n ear E d ju d in a ; A T in Discovery ; P rospecting Conditions ; Progress a t the Gold Mines ; New Power P lant.

V anco u v er... 363

A nnual R eport of the M inister of Mines for 1929 ; Alice Arm ; Anyox ; B rita n n ia Beach ; The K ootenays.

T oronto ... 364

S u dbury D is tr ic t; P o rc u p in e ; K irkland Rouyn ; P a tric ia D is tr ic t; M anitoba. Lake ;

Camborne ... 366

The Price of T in ; Effects upon L a b o u r; R estriction of O u tp u t ; Prospecting. Pe r so n a l ... 367

T r a d e P a r a g r a p h s

... 368

H a d field ’s D redge P a r t s ... 369

M e t a l M a r k e t s

... 371

S t a t i s t i c s o f P r o d u c t i o n

... 373

P r i c e s o f C h e m ic a ls

... 375

S h a r e Q u o t a t i o n s

... 376

Min in g Dig e st 356 F a n E fficiency . . R . A . H . Flugge-de S m id t 377 T h e P re se rv a tio n of M ine T im bers J . F . H arkom 380 D e p th C h arts ... J . M . M acintyre 382 T h e S te am Shovel in N ig e ria W . E . Sin cla ir 384 M anganese in th e U n ite d S ta te s d u rin g 1929 ... 387

C opper in C o n v e rte r Slag F . S. W artm an and W . T . Boyer 387 D e te rm in a tio n of C adm ium ... 388

Gold V alues in C opper O re s... 389

M icroscopic W o rk on S ulphide an d O xide O res ... 389

S h o r t N o t i c e s

... 389

R e c e n t P a t e n t s P u b l i s h e d

... 390

N e w B o o k s , P a m p h le ts , e t c

...390

C o m p an y R e p o r t s

... 391

Associated T in Mines of N ig eria; B angrin T in D red g in g ; B oulder P ersev eran c e; F abulosa Mines C on so lid ated ; Lonely Reef Gold M in in g ; O riental C onsolidated M in in g ; Oroville D re d g in g ; Peña Copper M in es; P e n g k alen ; Siamese T i n ; Tekka-Taiping. D iv id e n d s D e c l a r e d

... 392

N e w C o m p an ie s R e g i s t e r e d

... 392

6— 3

329

E D I T O R I A L

T H E 1930 edition of S kinner’s “ Oil and P etroleum Y ear Book ” is now published an d th e present issue is no less valuable th a n its predecessors as an in tern atio n al w ork of reference.

T H E news th a t Professor W. W . W a tts is to retire from th e chair of Geology which he has held in th e Im perial College since 1906 w ill be received w ith a feeling of regret. H e will be succeeded b y Professor P. G. H . Boswell, H erd m an Professor of Geology in th e U niversity of Liverpool, who is an old stu d e n t of th e College.

E L S E W H E R E in this issue will be found letters from th e R ector of th e Im perial College an d from D r. B aring H orw ood on th e subject o f “ The E d u catio n of th e E ngineer.”

F u rth e r editorial com m ent will be deferred for th e present, for doubtless others will wish to express th e ir views. I t is desirable, how ­ ever, th a t correspondents should n o t narrow down th e discussion, b u t keep it on th e broad lines indicated in our editorials.

T 'WO an n u a l dinners are being held th is m onth. To ta k e th em in chronological order, th a t of th e R oyal School of Mines is being held a t G a tti’s R e sta u ra n t, S tran d , on Ju n e 20, a t 7.15, under th e chairm anship of Mr. E d w ard H alse, w ith Professor W. W.

W a tts a n d Professor C. V. Boys am ong th e guests, an d th a t of th e In s titu tio n of Mining and M etallurgy a t th e H otel M etropole, N o rth u m b erlan d Avenue, on Ju n e 26, at th e sam e hour. T he an n u al general m eeting of th e la tte r w ill be held on th e sam e day, a t 3 o’clock, in th e room s of th e Geological Society.

A T T E N T IO N was directed in these columns in March, 1928, to th e concern felt a t the dangers of th e in troduction into th is co u n try of p etrol containing lead te tra -e th y l. A G overnm ent In te r-D ep a rtm e n tal Com m ittee of In q u iry has recently issued its rep o rt, w hich gives th is e th y l p etrol a clean bill of health. Careful stu d y of this report reveals th e fact, however, th a t th e efforts of th e investigators have been concentrated on detecting signs of lead poisoning whereas a tte m p ts should have been m ade to ascertain th e effects of lead te tra -e th y l—itself a m uch m ore dangerous poison— and th e e x te n t of them .

C OMMENT on th e position of silver was m ade in th e

M a g a z i n e

for J a n u a ry last, w hen th e m e ta l price had touched a record low level. Since th a t tim e the price of th e m e tal has continued to decline, reaching a new low level of 1 5 J |d . p er oz. on Ju n e 4. On Ju n e 8 a restriction on th e im p o rt of silver in to China was proposed ; th is w ould u n d o u b ted ly affect Chinese buying, w hich so far has been the m ain stay of th e price. In th e course of our com m ents in J a n u a ry it was suggested th a t the form ation of a silver research association m ight become necessary, and, as it seems prices can only hold b y increased m etal consum ption, th e tim e w ould appear to be ripe for the form ation of such a body.

T ^{H E recent} m ovem ent in W estern A ustralia for seceding from the Com m onwealth, on th e ground th a t the g ra n ts received are below those to which th e S ta te is en titled , has been followed by a representative delegation visiting th e E astern S tates w ith a view to securing for A ustralian gold producers a bonus of £1 an ounce on sta n d a rd gold won for a period of ten years.

In some q u a rte rs it is felt th ere is a con­

nexion betw een th e secession m ovem ent and th e proposed bonus. W hether th is is the case or n o t, there is no d o u b t th e granting of a bonus w ould prove advantageous to the m ining in d u stry an d W estern A u stralia’s proportion w ould be higher th a n th a t of the other S tates, as it is th e largest producer.

T H E restriction of th e o u tp u ts of th e tin m ining com panies b y 20 per cent, not having m et w ith th e resu lts anticipated, fu rth e r m easures are contem plated b y the Tin P roducers’ A ssociation, th e council of which has appointed a special com m ittee representative of M alayan, Nigerian, Bolivian, and D u tch in terests to deal with th e m atte r. A lthough th e m em bers of the com m ittee are sta te d to be in full agreem ent on all points, it has n o t so fa r announced its fu rth er recom m endations. In th e m eantim e there is a m ovem ent in th e E a st to close down th e B ritish-controlled com panies for tw o or three m onths, leaving th e smaller Chinese-owned properties a t work, in order th a t th e large num ber of coolies should not be throw n o u t of work.

T H E inclusion of tin m ines in a Home

Office silicosis schem e was d ealt w ith

b y our Cam borne correspondent in the

330

331 December issue. F u rth e r legislation is now

pending more clearly defining th e position and a t th e same tim e increasing the liability of producers. The new Bill proposes the addition of com pensation for p a rtial disable­

m ent, th e co-ordination of m edical arrange­

ments, and th e prohibition of em ploym ent in tin m ines of an y w orkm an who has been suspended in pursuance of th e scheme or who has refused or neglected to be exam ined under it. R epresentations are to be m ade by the responsible bodies in th e county against this additional legislation. Tin producers th e world over will be in h earty sym pathy, as it affects an in d u stry already afflicted by th e low price ruling for this metal.

A MONG th e B irth d ay H onours are several nam es of interest to the profession. Mr.

Basil M ott, on whom a b aronetcy has been conferred, received his education a t th e Royal School of Mines and is a well-known consultant and a p ast president of th e In stitu tio n of Civil Engineers. Mr. H erb ert W right, who receives a knighthood, is the chairm an of th e execu­

tive com m ittee of the governing body of the Im perial College, in w hich capacity he has done good w ork for m any years past. A knighthood has also been conferred on Mr.

E. H. M acartney, th e A gent General in London for Queensland, a n d on Mr. A. E. Faulkner, the U nder S ecretary for Mines a t the B oard of Trade. Mr. R. R. Simpson, Chief Inspector of Mines in India, receives th e C .I.E., Mr.

J. A. B. H orsley, E lectrical Inspector of Mines in th is country, th e O.B.E., and Dr. A rth u r W instanley, also on th e inspector­

ate in this country, th e M.B.E.

R E F E R E N C E was m ade in these columns in March, 1927, to a process for treatin g oxidized copper ores apropos o th er m e ta l­

lurgical advances. T his process has been considerably developed in th e in terim and following an o p p o rtu n ity of seeing a dem on­

stration on a lab o rato ry scale it is app ro p riate to give some details. The procedure consists in subjecting th e p reheated crushed ore to the action of sm all qu an tities of two simple reagents, carbon and common salt, cooling the reaction product, and floating th e finely divided copper m etal w hich results. I t is carried out continuously in the laboratory plant in ro ta ry kiln-type externally heated furnaces arranged in cascade, th e reagents in th e proportions of 2% carbon and |%

salt by weight of th e ore being added by m echanical feeder a t a point interm ediate

betw een th e preheating and th e reaction kilns. The ro tatio n of th e cylinder keeps th e charge in m otion. As to th e n a tu re of th e reaction, which it is h ard ly necessary to add occurs in a reducing or in ert atm o ­ sphere, this is tho u g h t to consist in two essential stages—the conversion of oxide, silicate, and suchlike to cuprous chloride, a n d th e subsequent reduction to m etal which appears on the surface of th e carbon particles.

The m etallic copper is often separated as pulverulent segregations, which have suggested th e popular nam e for th e process.

I t has been found th a t by a slight m odification of the process it is equally applicable to m ixed oxide-sulphide ores.

T he Steam S h ovel in Nigeria The despatch of a new steam shovel to N igeria has always been a m a tte r of some interest and the extent to which mechanical excavators have been tried on th a t mining field th u s became fairly well known. The m easure of success which has atte n d ed their em ploym ent, however, has always been difficult to determ ine as b u t little inform ation has been forthcom ing from those able to record th e progress of operations. The paper of Mr. W. E. Sinclair, therefore, on

“ Steam Shovel Mining in N igeria,” which was discussed a t the May m eeting of th e In stitu ­ tion, forms a welcome contribution to our knowledge of this m atter. In th e absence of Mr. Sinclair, who was on his w ay to this country from South Africa, the paper was briefly introduced by Mr. H um phrey Morgans and gave rise to a fruitful discussion. In th e paper—extracts from which will be found elsewhere in this issue—the history of each excavator appearing on th e P lateau is briefly recorded by the author, from the first dragline installed a t Liruei-n-K ano and the first shovel on Keffi Consolidated, and th e working difficulties encountered in each case are outlined, together w ith a record of fau lty lay-out and th e m anner in which such difficulties and m istakes m ight be overcome or rectified. W orking costs are th en briefly reviewed and, finally, the present position of th e use of mechanical excavators in N igeria is surveyed.

A fter th e introduction of the paper by

Mr. Morgans, the wisdom of using steam

shovels in Nigeria was strongly questioned

by Mr. Brodigan, who, in the first place,

pointed to th e large capital expenditure

involved in th eir installation. He referred

also to th e scarcity of w hite labour on th e

P latea u and pointed out th a t th e dependence

332

of w ork in h an d on th e shovel operator ra th e r m ilita te d against efficiency an d m ade it im perative th a t n ativ e lab o u r should be tra in e d as speedily as possible in th e handling of th e m achines. Mr. B rodigan also deplored th e lack of exact figures in th e pap er and suggested th a t m echanical excavators were n o t a success on th e field. Several other speakers ra th e r su p p o rted Mr. B rodigan’s a ttitu d e , which was opposed, however, by Mr. T rew arth a-Jam es, who called a tte n tio n to th a t section of th e p ap er w here th e a u th o r lays down th a t in each case th e ex cav ato r h a d done all th a t was dem anded of it. Mr. T rew arth a-Jam es was supported b y Mr. W. B arnes, of R uston-B ucyrus, an d b y Mr. D. J . Ringwood, of R ansom es an d R apier.

A ny a tte m p t to assess th e degree of success w hich has a tte n d e d th e use of m echanical excavators in N igeria m u st ta k e account of th e fact th a t on this field th e use of m achinery has ever been considered as foredoom ed to failure an d even a t th e present tim e th e in stallatio n of any new m echanical device is viewed w ith d istru st. In such an atm osphere it is n o t surprising th a t inform a­

tion ab o u t th e use of th e N igerian shovels has been som ew hat conflicting. To an outside observer th is a ttitu d e of d istru st is, perhaps, difficult to u n d erstan d , as an exam ination of th e w ork of m echanical excavators in oth er p a rts of th e w orld shows th a t, correctly applied, th e y cbuld well do sim ilar w ork in Nigeria. If a steam shovel can rem ove th ick overburden from a thin seam of coal in th e U.S.A. an d re-p ay th e large cap ital expenditure involved th ere is no ap p a re n t reason w hy sim ilar w ork could n o t be done in N igeria over a tin - bearing gravel. Again, an exam ination of th e finances of N igerian com panies m akes it ap p are n t th a t in m an y cases th e ca p italiza­

tio n could only be w a rra n te d b y large o u tp u ts a n d th a t such large o u tp u ts could only have been ensured b y th e installatio n of m echanical excavators capable of handling enorm ous yardages of overburden. As was noted during th e discussion of Mr. Sinclair’s paper, th ere have been no faults in th e m achines w orking on th e P late au , w hich are all doing w ork w hich w ould otherw ise call for enorm ous supplies of w ater and labour, w ith n eith e r of which, as th e a u th o r pointed out, is Nigeria plentifully endowed. I t is evident, however, th a t, although no fau lt can be found w ith the m achines, th e ir installatio n on th e field has n o t alw ays been carried o u t in an efficient m anner. U sually too m uch w ork has been

dem anded of th em — in oth er words, a m achine of too sm all a cap acity has been installed— th e lay -o u t of th e w ork has been faulty, an d th e m anagem ent of white operators has n o t alw ays been carried out w ith th e firmness an d ta c t dem anded.

F inally, it w ould ap p ear th a t, w hilst there is nothing w rong w ith th e shovel in Nigeria, its in stallatio n an d handling have n o t always been all th a t could have been desired.

T h e F u tu re o f th e Rand

The life of th e R a n d goldfield—or, as those in th e insurance w orld w ould express it, th e ex p ectation of life—has for long been th e concern of those who for one reason or an o th er are dep en d en t on th e m aintenance of its prosperity. T he tim e following the publication of th e rep o rts of th e big corpora­

tions controlling th e operations of th is field seems to be an o p p o rtu n ity for some fu rth er consideration of th is alw ays interesting and deeply significant subject. In p articular some of th e observations m ade b y the chairm an of th e C entral M ining group provide m aterial for com m ent an d discussion.

Sir Sothern H olland, recording his im pression of a recen t v isit to S outh Africa, was disposed to deplore th e w a n t of tho u g h t or trouble being given to th e problem , which th e U nion w ill have to face, of th e progressive contraction of th e in d u stry an d this, m ore­

over, in spite of rep eated w arnings from those com petent to judge th e tre n d of events. As he pointed out, in an age w hen th ere is over­

production of alm ost every raw m aterial th e dem and for gold persisted and, in fact, tended to increase. This being so, and n o tw ith stan d in g th e in d u strial developm ent of th e U nion as a whole, th a t c o u n try is still dependent pre-em inently on th e prosperity of its gold-m ining in d u stry . H e referred also to th e tendency in some q u a rte rs there to reg ard th e p latinum -producing in d u stry as capable of tak in g th e place of th e declining older in d u stry , b u t th e statistics enabled him effectively to dispose of th is fallacy, for such it is. M aking th e m ost generous allow­

ance for increased consum ption a t a lower price, it can be shown th a t if S outh Africa produced th e whole of th e w o rld ’s require­

m en ts of p la tin u m th e revenue to th e S tate w ould be betw een th ree a n d four million pounds only, or ra th e r less th a n th e value of th e o u tp u t of th e Crown Mines alone.

F u rth e r, em ploym ent w ould be found a t best

for some 1,000 w hite m en an d 10,000 natives

and the p la n t an d stores req u ired w ould be

333 less th a n half th a t needed to equip and run

a gold m ine of th e size of th e properties controlled by th e com pany m entioned.

It should be rem em bered th a t th e Central Mining C orporation is itself interested in platinum production, so th a t these rem arks are to be regarded as q uite unbiased.

Coming to th e gold m ines of th e W itw aters- rand and th e steps necessary to help and m aintain th e in d u stry so im p o rtan t to South Africa, and in tu r n to th e E m pire as a whole, these can only ta k e th e form of reduction of working costs to bring m ore an d m ore low- grade ore into th e region of payability.

Various m eans suggest them selves and others will, no doubt, be found w hen th e question comes to be exam ined m ore closely, as it will sooner or later. T he G overnm ent m ight sacrifice some revenue to -d ay an d th e colour bar restrictions m ight be som ew hat modified, ap art from technical im provem ents tending to bring down expenditure, while it is felt th a t th e opening of new areas in th e F a r E ast R an d w ould be facilitated b y some revision of th e Mining Leases Act.

Our Johannesburg correspondent in his letter last m o n th recorded a debate in the Union P arliam ent, a t th e instigation of Sir R obert K otze, w hich was aim ed a t riveting a tte n tio n on this m a tte r and as a result a G overnm ent investigation has been promised. Sir R o b ert disclosed th a t a reduction of costs would have th e effect of making w orkable so m uch more ore th a t the increased p ro sp erity to th e in d u stry would result in th e S ta te being reim bursed for any sacrifice it m ight make. A t any rate, a sufficient case for enquiry seems to have been made and th e forthcom ing deliberations will be followed w ith close a tten tio n , n o t only in the Union, b u t also in th is country.

E m pire U nity

Much pu b licity has lately been given to schemes for the consolidation and develop­

m ent of th e E m pire and the appeal for Free Trade w ithin its confines is becoming a political issue of th e first im portance.

The ideal of an E m pire as a closely-knit economic whole has been set up and is finding a ready acceptance am ong an increasing body of people whose enthusiasm is not easily dam ped. The p racticability of this w orthy ideal is b eyond our province to discuss, b u t, so far as readers of the

M a g a z in e

are concerned, it will be recognized th a t th e m ining engineering profession for its p a rt is striving through the m edium of

triennially-convened congresses to cem ent th e bonds of E m pire in the m ining and m etallurgical industries. A m id all this semi-political, semi-economic, com plexity there is an aspect of the m a tte r which seems to be of specific interest to th e engineer himself, bearing on th e developm ent of the E m p ire’s m ineral resources. I t has been said th a t the em ploym ent of foreign capital for the exploitation of colonial m ineral w ealth is to be regarded as an ything b u t disadvan­

tageous, since the “ foreigner who is assisting in th e discovery and m ining of n a tu ral resources is adding to the w ealth of th a t country ’ ’—to quote from the

M a g a z in e

of F e b ru a ry last.

Fundam entally, as an economic theory, th e foregoing is a sound view th a t will, as we have said on a previous occasion, be generally endorsed. There is, however, a concom itant of foreign financial participation which m ay have undesirable effects. Viewed from the broad stan d p o in t of purely economic reasoning, th e opinion about to be expressed m ay be regarded as parochial, b u t it is nevertheless of such im portance to mining men th a t in th eir interest it m ay well be advanced.

The question of th e desirability or otherwise of the enlistm ent of foreign capital for the conduct of operations on B ritish territo ry largely depends on how far th is participation carries w ith it th e power to control those operations. Foreign control per se m ay be unobjectionable economically. W hen, how­

ever, it carries w ith it th e preferential selection of technical executives of other th an B ritish nationality, som etim es regardless of efficiency, it seems tim e to tak e notice.

This m ay be regarded as a charge of adm inis­

tra tiv e inefficiency, b u t, hum an n atu re being w hat it is, does it not happen th a t selections are often m ade from m otives of sentim ent ? This is a contingency th a t has to be faced and, in fact, has been faced in isolated instances.

A repercussive effect of th e em ploym ent of foreign technical m en in m ining and m etallurgical activities in th e Dom inions and Colonies is sometimes to be found. Trade follows th e flag ; th e m anufacturer is heavily indebted to th e pioneer and the colonist.

These som ew hat sententious observations have their m odem equivalent, inasm uch as m achinery is said “ to follow th e engineer.”

H ere again sentim ent plays a considerable

p a rt and the m akers of m ining p la n t and

m achinery in this country would feel more

confident of receiving consideration from

executives of their own nationality.

R E V I E W O F M I N I N G

In trod u ction . — Business continues to be very dull an d th ere are as y e t few signs of a revival. The issue of th e Simon R ep o rt will a t th is stage only ad d to the In d ian confusion, although, after consideration of its contents, it is to be hoped th a t conditions in th a t co u n try w ill im prove. Such an im provem ent w ould give a m uch-needed im petus to trad e in th is country.

T ran svaal. —The o u tp u t of gold on the R an d during May was 876,893 oz. a n d in outside d istricts 39,320 oz., m aking a to ta l of 916,213 oz., as com pared w ith 868,606 oz.

in April. A t th e end of M ay th e num ber of natives w orking in th e gold m ines was 202,182, as com pared w ith 202,434 a t the end of April.

A t the an n u al m eeting of th e New Steyn E s ta te Gold Mines, held in Johannesburg, it was announced th a t th e com pany a n d the liq u id ato rs of R oodepoort U nited were considering a fusion of in tere sts in order th a t a scheme m ig h t be launched w hen conditions are favourable.

The first rep o rt on th e w ork of th e W aterv al (R ustenburg) P latin u m Mining Company, w hich covers th e period of eight m onths since production comm enced, shows th a t 78,400 to n s of ore, averaging 7 dw t., was tre a te d for a to ta l recovery of 11,231 oz.

of p latin u m group m etals. G rav ity concen­

tra tio n only was em ployed, b u t experim ents on th e tre a tm e n t of tailings b y a flotation process have h a d encouraging results. The com pany sold 7,654 oz. of m etal, which realized £73,424, or £9 11s. p er oz. The m etals recovered contained over 80%

p latin u m , 14% palladium , a n d 5% gold.

The reef is very narrow , only 16 in. in stoping w idth, an d an u n d erh an d resuing m ethod of m ining has been found su itab le for ex tractio n .

S ou th ern R h od esia. —The gold o u tp u t of Southern R hodesia for April was 45,806 oz., as com pared w ith 45,511 oz. in M arch and 48,210 oz. in A pril of 1929. O ther o u tp u ts in A pril were : Silver, 5,989 oz. ; copper, 143 tons ; coal, 88,808 tons ; chrom e ore, 21,357 tons ; asbestos, 2,516 tons ; mica, 1 ton.

Intensive prospecting w ork in S outhern R hodesia w ill be u n d erta k en by a new com pany, th e V ictoria Prospecting Co., to which a special m ining gra n t has been m ade by th e B ritish S outh A frica Com pany, w ith th e a p p ro v al of th e G overnm ent of Southern Rhodesia. The new com pany will have a ca p ital of £150,000 in 300,000 shares of 10s. each and th e m anagers and consulting

engineers are R hodesian Anglo American, L td . I t is und ersto o d th a t th e g reater p a rt of th e cap ital w ill be subscribed b y the principal R hodesian an d T ran sv aal mining an d finance groups. The g ra n t itself covers an area of ap p ro x im ately 9,000 sq. miles, situ a te d to th e east an d south of F ort V ictoria a n d extending to th e Portuguese frontier, and will th u s include portions of th e Victoria, N danga, B ikita, and M elsetter districts.

N orthern

R h o d e s i a . —

The report of R hodesian Anglo A m erican, L td ., for the period from th e incorporation of th e com­

p an y (December 8, 1928) to M arch 31 last shows a gross revenue from all sources of £746,425 and an u n a p p ro p riated profit of £323,603. T he com pany has im portant holdings in th e B w ana M’K ubw a Copper Mining Co., R hodesian Congo B order Con­

cession, L oanga Concessions, Rhodesia B roken H ill, and th e B ritish South Africa Company.

A progress rep o rt issued b y R oan Antelope Copper Mines, L td ., sta te s th a t during the th ree m onths ended M arch 31 last the statio n on th e 420 level of th e B e a tty shaft was com pleted an d sinking operations resum ed. The erection of new steel headgear a t No. 2 shaft is in h an d and a 500-gallon centrifugal pum p has been in stalled in the old 420 pum p station. In ad d itio n a new sum p a n d a sta tio n for tw o sim ilar pumps are being prepared. T he sinking of th e upper portion of No. 5 Supply Incline, which will serve th e flat stoping area in th e “ nose ” of th e syncline, has been s ta rte d from surface ; lower portions will be raised. Im proved labour available tow ards th e end of the q u a rte r gave an im petus to th e w ork in hand, th e to ta l com pound stre n g th increasing to 3,860 “ boys ” a t th e end of March. At an e x trao rd in ary m eeting held on Ju n e 10 th e creation of £2,500,000 debenture stock was authorized, arrangem ents having already been m ade for th e issue of £1,500,000, which will be redeem able in 15 years an d carry in tere st a t 7% , in addition to having option rights.

The rep o rt of N ’C hanga Copper Mines, L td ., for 1929 sta te s th a t w ork during the year was confined to drilling operations on b o th lim bs of th e syncline a n d to a lim ited a m ount of u nderground w ork on th e northern lim b. On th e R iver Lode th e v ertical shaft was sunk to 634 ft., b u t cross-cutting has been suspended owing to lack of power.

The first shaft, No. 10, has been s ta rte d on

334

335 the “ New D iscovery ” area an d the in stalla­

tion of pow er-plant is in hand. The present drilling policy is being directed tow ards the discovery of sulphide ore an d w ork is in progress w hich will prove w hether the rich sulphides encountered on the lower horizon in th e adjoining area of the Rhodesian Congo B order Concession extend in to the N ’Changa area. A bout th e m iddle of May, however, shareholders were inform ed of the results o btained from bore-hole B.39 which showed th a t th e lower banded shale horizon at th is point is 12 ft. thick, averaging 9-5%

copper, of which only 25-3% is in the form of sulphide.

A progress rep o rt issued by M ufulira Copper Mines, L td ., which deals w ith the work done to M arch 31 last, shows th a t considerable difficulty is being experienced in the conduct of m ining operations owing to water. No. 2 sh aft was stopped early in February, while No. 3 was sunk to th e 620 ft.

level an d driving commenced on the 380 ft.

level. Owing to th e presence of w ater under pressure, however, provision w ill have to be m ade for pum ping-sum ps an d th e n a tu re of the ground is m aking th is difficult. No. 4 shaft was advanced to th e 433 ft. level, 70 ft. of driving being done a t th e 250 ft.

level for sum ping purposes, and No. 5 shaft was sunk to 90 ft.

Shareholders of the R hodesian Selection T rust have been inform ed of th e results from two new bore-holes. Bore-hole No. 3 at Kasaria, on the Luansobe special grant, entered ore a t 955-5 ft. a n d passed through 3-9 ft. tru e w idth of sulphide ore, averaging 5-42% copper. On th e Cham bishi special grant bore-hole No. 35 entered ore a t a depth of 1,180 ft. and showed 25 ft. tru e width of sulphide ore averaging 6-85%

copper, of which th e lower 107 ft. averaged 12-78% copper.

U gan d a. —An offer to shareholders of Kagera (Uganda) Tinfields, L td ., m ade on behalf of th e B illiton Tin Company, to take their shares a t 7s. 6d. per share, provided th a t the holders of 150,000 shares accepted the offer by Ju n e 2, has been accepted.

The B illiton Com pany is to provide the K agera com pany w ith sufficient capital for developm ent during the next two years.

N igeria. — D uring the year ended October 31 last th e o u tp u t of tin concentrates by the K ad u n a Syndicate was 464 tons, as against 382J tons in 1927-28, the net average price realized being ¿126 17s. 6d. per ton, against ¿140 Is. 9d. The profit was increased from ¿17,201 to ¿26,218, while a sim ilar

dividend of 20% , absorbing ¿8,000, was paid during th e year. The com pany is interested in Mavoc, L td ., prospecting in Sierra Leone, and in E ast African Explorers, L td ., which has applied for prospecting and mining rights over tin-bearing ground in Nigeria.

In spite of a reduced o u tp u t of tin concen­

tra te s—288 tons, against 310 tons for 1927-28—the profit of th e K aduna Pros­

pectors for th e year ended O ctober 31 last was ¿13,138, as com pared w ith ¿10,085 for 1927-28. D ividends totalling 10%, absorbing

¿3,000, have been paid, as com pared w ith 20% in the previous year. The price realized for its product was ¿131 17s. 10d., against

¿145 11s. Id . I t is proposed to increase the capital of th e com pany to ¿60,000 b y creating 80,000 new shares of 5s. each, although any issue in th e near fu tu re is not contem plated.

A u stralia. — An issue of ¿1,500,000 8%

Convertible an d R edeem able D ebenture Stock was successfully m ade by M ount Isa Mines, L td ., tow ards th e end of May. The rep o rt of the technical com m ittee, which was a ttach ed to th e prospectus of th e issue, was noticed in these columns last m onth.

In a circular to shareholders of th e R oper River L and an d Minerals Com pany, L td ., it is sta te d th a t an option h as been acquired over lead properties situ ated in th e Camden D istrict of New South W ales. The properties, which cover 527 acres, comprise th e Colon Peaks, Silver Peaks, and Silver K ing leases.

The lead m ineral is galena and is said to contain values in gold and silver. A report on th e p ro p erty has been m ade b y Mr. F. B.

T rude and th e purchase price is ¿16,667 an d ¿2,000 payable out of th e proceeds of the first sales of ore produced. To provide the necessary w orking capital of ¿20,000 the com pany will be reconstructed, shareholders being given th e rig h t to ap p ly for two shares of 5s. each in th e new com pany, w ith a liability of Is. 3d., for each 10s. share now held.

D uring 1929 the m ill of the Sons of Gwalia tre a te d 118,328 tons of ore and 43,512 tons of accum ulated sands and slimes, the to ta l o u tp u t of gold being 30,929 oz., which realized ¿131,161. W orking costs were kept low, b u t m ainly due to the grade of ore tre a te d there was a loss for th e y ear of

¿2,678. Severe tem p eratu re conditions a t d ep th continue to delay th e opening up of the lower levels.

Modifications in th e original plans for the developm ent of th e W iluna Gold Mines and th e decision to spend m ore m oney on accom­

m odation an d am enities for work-people m ade it apparent th a t m ore capital would

I

336

be required. Tow ards th e end of 1929 it was estim ated th a t £550,000 would be necessary. Of th is sum th e W est A u stralian G overnm ent has unconditionally guaranteed th e provision of cap ital a n d inte rest on

£300,000 6% seven-year notes, w hich have been placed in London. I t is in ten d ed to give shareholders th e o p p o rtu n ity of p a rti­

cipating w hen it is decided to issue th e balance.

M alaya. —D uring 1929 the T anjong Tin Dredging, L td ., tre a te d 1,420,350 cu. yd.

of ground, th e o u tp u t of tin ore being 372 tons, as com pared w ith 437 tons in 1928.

The to ta l revenue was £46,391 an d th e w orking profit £23,113, th e la tte r com paring w ith £34,114 th e year before. D ividends to tallin g 20% absorbed £16,000, against

£20,000 th e previous year.

The o u tp u t of K in ta T in Mines for 1929 was 3 6 8 | to n s of tin ore from 962,500 cu. yd.

of ground. T he to ta l revenue was £46,341 and th e w orking profit £30,182, as com pared w ith £33,244 in 1928. D ividends paid during th e y ear absorbed £24,000, equal to 20% .

D uring 1929 th e o u tp u t of Id ris H ydraulic Tin was 450 tons, or 102 tons less th a n in 1928, an d th e average price realized per to n was £114 6s. 6d., as com pared w ith

£125 4s. lOd. The revenue fell from £69,286 to £51,746 and th e profit from £47,584 to

£30,608. D ividends a t the ra te of 20%

absorbed £24,000.

India. —The rep o rt of th e In d ian Copper C orporation for 1929 sta te s th a t 80,151 short tons of ore was m ined during th e y ear and 1,635 tons of refined copper was produced.

The ore reserves were increased b y 42,111 short to n s an d a t th e end of th e y ear were estim ated to be 797,741 short tons averaging 3-32% copper. Sales of k y an ite from th e K harsaw an area increased from 1,951 tons to 3,432 tons. T he profit for th e y e a r’s w orking was £45,415.

B urm a. —A t an e x tra o rd in a ry general m eeting of A nglo-B urm a Tin to be held this m o n th it will be proposed th a t each of the unissued shares of £1 be divided into four shares of 5s. each, an d th a t th e c ap ital be reduced from £250,000 to £121,000, divided in to 484,000 shares of 5s. each. W hen th e reduction has been confirm ed th e ca p ital will be increased to £250,000 an d a t th e same tim e it is proposed to create £80,000 in debentures.

Spain . —T he E sp eran za Copper and Sulphur Com pany reports an increase in th e production of p y rites during last year, th e

developm ent of th e E sp eran za m ine below th e b o tto m level being prom ising. In Cyprus a s ta rt was m ade w ith th e re-opening of th e L ym ni m ine of th e Cyprus S ulphur an d Copper Co. a n d w ork is s ta te d to be proceeding satisfactorily. T he profit for 1929 was £20,799 an d th e dividend of 7%

recom m ended will absorb £19,031.

A n g lo -O rien ta l M ining C orporation.

— A t an e x tra-o rd in ary general m eeting of th e A nglo-O riental Mining C orporation, held a t th e close of th e an n u al general m eeting last m o n th , th e proposal to increase the authorized capital of th e corporation to

£1,750,000 b y th e creation of 1,000,000 new ordinary shares of 5s. each was approved.

C entral M in ing and In vestm en t C orporation. —The acquisition of a n in terest in tw o tin-m ining com panies operating in Bolivia, following a rep o rt b y D r. Malcolm M aclaren, was announced a t th e annual m eeting of th e C entral M ining an d In v e st­

m ent C orporation, w hich was held last m onth.

A m ining engineer from th e R a n d has taken over th e m anagem ent of th e properties and a com prehensive scheme of developm ent is being prepared.

C o n so lid a ted G old F ield s o f South A frica . —T he fusion of three investm ent tru s t com panies largely in terested in the S outh A frican m ining in d u stry has been sanctioned b y shareholders of th e respective un d ertak in g s—th e C onsolidated Gold Fields of S outh Africa, th e S outh A frican Gold T ru st, and th e A m algam ated Mining T rust.

Consolidated Gold Fields will acquire the assets a n d un d ertak in g s of th e oth er two com panies b y an exchange of shares, and will increase its F irst Preference cap ital by

£500,000 and its O rdinary C apital by

£

1

,

000

,

000

.

C on so lid ated T in S m elters. —A t the s ta tu to ry m eeting held a t th e end of May it was announced th a t th e m erger contem ­ p la te d on th e form ation of th e com pany in Ja n u a ry last h a d been ratified b y th e share­

holders. I t w ill be rem em bered th a t a necessary condition for ratification was th a t th e holders of 90% of all classes of shares in each of th e am algam ating com panies—

th e nam es of w hich were given in th e

M a g a z in e

for J a n u a ry la st— should agree to exchange th e ir shares.

M urex, Ltd. — In order to acquire over

99% of th e shares of Alloy W elding Processes,

L td ., th e b o ard of M urex, L td ., propose to

increase th e cap ital of th e com pany by

creating 100,000 new shares of 10s. each.

OBSERVATIONS ON T H E GEOLOGY AND MINES OF T H E BELGIAN CONGO'

By G. V IB E R T D O U G L A S

In this article the author, who is the Chief Geologist to the R io Tinto Company, gives some notes taken during a recent visit to the Katanga.

G e n e r a l G e o l o g y . —

In discussing the general geology of th e K atanga, it is neces­

sary to consider a broader area th a n th a t prescribed by th e international boundary and it will be necessary therefore to m ake frequent m ention of th e p arts of N orthern R hodesia which have a bearing on th e subject.

sim ilar folds in N orthern Rhodesia," while th e nappes and th ru s t blocks of th e Alps find their equivalent in the Belgian Congo.

Following, or during, this period of crustal deform ation there was a period of^igneous activity, during which acid and^ basic rocks were injected into th e overlying.form ations.

D uring the closing stages of this activity

Fi g. 1 .— Fl o o d e d Op e n-c a s t o f t h e Et o i l e d u Co n g o m i n e.

The sedim entary rocks of the K atan g a and p a rts of R hodesia would appear to have been laid down in a g reat inland basin as fresh w ater shallow deposits. Following its deposition and th e later uplift which drained the basin, there ensued a period of m ountain building in which th e rocks were folded and crumpled. The axis of this line of m ountain- built stru ctu res tren d s N .W .-S .E . In Rhodesia th e folding was com paratively gentle, w hereas in th e K atan g a the rocks were not only folded b u t were th ru s t over the younger form ations in a num ber of places. T he directions of the forces which produced this m ovem ent were either from the N .E. or S.W ., depending on w hether one considers th e operation as one of under- thrusting or overthrusting.

An E uropean parallel m ay be draw n between th e African stru ctu res and those of the Alps and Ju ra . The anticlines and synclines of th e J u ra can be likened to the

1 P u b lish e d w ith th e perm issio n of th e C h airm an

of

th e R io T in to Co., L td .

th e m ineralization was supposed to take place. I t should be noted here th a t there is a difference of opinion am ongst the geologists of th e Congo and those of R hodesia as to the tim e of this m ineralization. A discussion of this point will be found in a later section.

Follow ing the events as ju st outlined, erosion reduced the whole area to a pene­

plain. In th e course of this erosion th e crests of m an y of th e anticlines and nappes were rem oved, and in places the basem ent rocks were exposed. W here sulphide m ineraliza­

tion existed the action of th e surface waters and of th e gases of the atm osphere began to alter th e original com position of the m inerals contained in th e rocks. The con­

siderable depth to which oxidation has p en etrated in the areas here considered points to the fact th a t arid conditions m ust have prevailed.

A t the present tim e (1930), the geographical lim its of these folded rocks have only been determ ined in a very general way. In the Congo their range is from th e

1

338

south-east corner of th e Belgian T errito ry to some point a little to th e w est of Musonoi or th e centre of th e w estern group of mines.

This stre tc h is a p p ro x im ately 400 miles.

In N o rth ern R hodesia th e p o te n tia l range of th e copper-bearing series is of th e order of 200 miles. In m aking these statem en ts tw o facts m u st be borne in m ind— first, th e m apping of th e rocks in N orthern R hodesia is b y no m eans com plete, and secondly, erosion having cut down th e series to a m uch g reater degree south of th e frontier, there is less continuity. This lack of co n tin u ity m eans th a t there are only patches of th e copper-bearing series left.

I t is tru e th a t some of these patches are of considerable ex ten t, b u t, nevertheless, there is n o t th e evident c o n tin u ity of th e beds such as is seen in th e K atan g a. This is one reason for believing th a t th e m ineral deposits of the K a tan g a are p o te n tia lly g reater th a n those in Rhodesia.

In th e accom panying table th e form ations occurring w ith in th e K a ta n g a system are shown as set out b y R obert and Van D oorninck.

M i n e r a l i z a t i o n .

—T he problem of the relatio n of m ineralization to th e period of m o u n tain building m ight app ear a t first sight to be only of academ ic interest. It has, however, a very live economic aspect, especially to those in th e Belgian Congo, as th e following discussion will reveal.

The problem s can be briefly sta te d thus : W ere th e ores in tro d u ced into th e rocks of th e m ine series of th e Congo an d th e copper bearing series of N o rth ern Rhodesia, before or a fter those rocks were crum pled, and were th e ores in th e tw o countries introduced at th e sam e tim e ? Also, are th e ores epigenetic or syngenetic w ith th e beds in w hich they are form ed ?

T aking these problem s in th e reverse order to th a t w hich th e y are sta te d , it m ay be said th a t th e geologists in N o rth ern Rhodesia a n d th e Congo consider th a t th e ores in the m ines of th is large area are epigenetic, th a t is to say th e y were introduced into the beds a fte r these beds h a d been laid down and consolidated. Some m em bers of th e XV In te rn a tio n a l Geological Congress, however, n o tab ly Professor Schneiderholn, considered

Ta b l e o f Ge o l o g i c a l Fo r m a t i o n s i n t h e Be l g i a n Co n g o

M . Robert’s C olum n through M oachia A n ticlin e.

U p p e r K undelungu.

V an D oorninck's C olum n.

L ow er K u n d e lu n g u .

S ystèm e S chisto- d o lo m itiq u e c h e rte u x ( = M o a c h ia ).

Série des M in e s .

M tre. M tre.

L im e & sa n d y sc h ist 10 P la te a u A rkose. A rkose . 200 P in k ish lim e sto n e . 15

L ittle Conglom. 15 S an d sto n e.

K a t e t e . S hale, L im e sto n e,

S a n d y , felsp ath ic L ittle Conglom.

lim esto n e 40 L im e L im e S hales . 3,000

A rgil, sch t. 200 S hale K a k o n tw e lim esto n e

K ak o n tw e lim esto n e Series. C alcareous shales.

a n d calcar, s c h t .. 50

C onglom erates 200

K a ta n g a T illite. S hales . —

G re a t Conglom. 350 A rkose . 800

F els. S.S. 5

A rgil, scht. 20

Fels. S.S. 20 A rkose . 100

A rgil, scht. 200 to

B lac k sc h t. 100 L im e shales . 500

L im e sto n e an d lim e M w ashya.

sch t. . 100 O olites.

Conglom. 1-5

G reen, g re y lim e ­ sto n e so m etim es schistose & sa n d y 60 O olites, ja s p e r a n d

h aem atite 10

D olom ite 200 Série des M ines. T h e sam e as in R o b e rt's

D olom itic shales. C olum n.

C ellular q u a rtz ite . F eu illetées o r b an d e d to

q u a rtz ite . In fe rio r o r low er

shales 400

t

o £ H

<

«

<

W

X

in>

i

N .B .— G eological colum ns of o th e r w rite rs a re g iv en in V an D o o rn in c k ’s M em oir.

339 th a t th e ore was syngenetic, th a t is, laid down

as an integral p a rt of the sediments.

The field evidence seems, in the opinion of the w riter, to be in favour of an epigenetic origin. Some of th e reasons are :—

(a)

T he association in R hodesia between the ores, th e sedim ents, and th e intrusive bodies of g ran ite and pegm atite. There is a definite p a tte rn on th e geological m aps of the M’K an a Mine, the R oan Antelope Mine, Mufulira and N ’Changa. W here the copper bearing series is in close p ro x im ity to the

phenom ena can be seen a t the R oan Antelope mine.

(e) There appears to be a definite con­

nexion in N orthern Rhodesia between the m ineralization and drag folds. This point has been especially em phasized by Dr. J. A.

Bancroft.

R egarding th e question of w hether we are dealing w ith tw o periods of m ineralization or one period, it m ay be stated th a t owing to th e association of th e ore m inerals in both countries the probability is in favour of one

Fi g. 2 .

intrusive granites or is caught between two boss-like bodies, as a t N ’K ana and the Roan, there th e ore is found to be present.

In the Congo and a t B w ana M’K ubw a this field relationship is n o t apparent, possibly because the granite masses, if present, have not been revealed by erosion.

(b) The microscopic evidence is in favour

of m ineralization later th an the form ation of the beds.

(c) A t some of the N orthern Rhodesian mines th e m ineralization is not confined to any one bed, b u t jum ps from one horizon to another along th e same flank.

{d) In th e opencast at L uushia a veinlet

of chalcopyrite and kyanite (disthene) could be seen cu ttin g th e shales norm al to their bedding planes. On a sm aller scale, similar

great m etallogenetic epoch. The association of m inerals containing copper and cobalt is som ew hat rare, and is common alike to the K atan g a an d R hodesian deposits.

The m ajor problem of th e tim e relations of m ountain building and m ineralization rem ains unsolved. According to the geologists of th e U nion M inière du H a u t K atanga, th e ore m inerals were introduced into the rocks of th e Série des Mines before m ountain building took place.

The argum ents in favour of th is contention m ay be sta te d as follows. Firstly, the m ineralization is in the beds of the Mine Series and is uniform ly d istributed. This is th e argum ent advanced by M. Richet.

Secondly, th e faults an d th ru st planes are

not m ineralized. A lthough there is a

340

trem endous am o u n t of talc developed in th e th ru s t planes, w hich will m ake these planes alm ost im perm eable, y e t th e fact th a t the faults, as distin ct from th e th ru s t planes, are no t m ineralized p resen ts a form idable arg u m en t in fav o u r of th e Belgian contention.

I t m ay be n o ted here t h a t th e w rite r found on th e dum p a t th e E toile a specim en of a d istin ct breccia, in w hich th e angular fragm ents of rock were cem ented b y copper carb o n ates an d chrysocolla. H e was n o t able to find th e place w here th e specim en cam e from. This find, however, casts some d o u b t on th e v a lid ity of th e second argum ent.

T h ird ly , th e K undelungu shales, which are

tio n was accom panied by silicification. The resulting q u a rtz veinlets are found only in th e Série des Mines. T his sta te m e n t precludes th e possibility of th e ore m inerals having been com pletely hacked out of th e crushed zones, th ereb y leaving no trace.

T he general opinion of th e geologists of Rhodesia is th a t th e ore-deposits are post m o u n tain building, a view diam etrically opposed to th a t of th e Belgians. The evidence for this view m ay be sum m arized as follows : F irstly , fresh p eg m atites are to be seen in some of th e R hodesian m ines cu ttin g the beds of th e B w ana M’K ubw a series. I t is difficult to conceive th a t these could have

5 K e f c h S e c t i o n o f R u o s h t O p e n c a s t {g a n g w est a b o u t m id w a y on th e A x is

S u r fa c e

m e ta rge p ro d u c in g m m e s o f th e Congo

F lo o r o f O p e n c a s t

5 K e tc h S e c tio n a t W est E n d ■ fCuasht Fi g. 3 .

younger th a n th e Mine Series, b u t upon which th e Mine Series have been th ru st, are supposed to be barren. In one place in K ipushi, this sta te m e n t is false, for if one can believe th e rum ours from this sanctum of secrecy th e ore is th ere in th e K akontw e L im estone of th e K undelungu. F u rth erm o re, th e shales of th is age below th e Mine Series have n o t been explored to an y ex te n t. Finally, in places, as in th e H o sp ital P it a t L uushia, th e Mine Series carrying sulphides as well as oxides have strikes norm al to th e th ru s t planes. In a num ber of places sulphides have been proved b y drilling down th e dips of these beds. F u rth erm o re, th e m ineraliza-

been in jected p rio r to th e folding of th e beds As has alread y been indicated, th e ores are connected w ith th e cooling phases of the granitic m agm a from whence also came the p egm atites. Therefore, if th e pegm atites are later, so also are th e ores. Secondly, it has been previously m entioned th a t th e ores are associated w ith d rag folding. This co n stitu tes a v ery strong proof for a m ineralization la te r th a n th e folding. Finally, th e veinlets in th e open cast a t Luushia, w hich hav e been referred to , are a lso positive evidence.

In reviewing these “ pros ” an d “ cons ” ,

it m u st be a d m itte d th a t th e re is strong

341

Fi g. 4 . — Ru a s h i Op e n-c a s t— Fa c i n g Ea s t.

evidence on b o th sides ; however, it will be seen th a t th e R hodesian evidence is of a more positive character th a n th e Belgian.

The following conclusion m ay therefore be made. I t is extrem ely unlikely th a t we are dealing w ith two periods of m ountain building. I t is also unlikely th a t there have been two periods of m ineralization on account of the rare association of m inerals of copper and cobalt. Therefore the evidence, although conflicting and difficult of in terpretation, points on th e whole to an epigenetic and post-tectonic period.

T urning from these ra th e r theoretical

b u t nevertheless im portant considerations to th e facts concerning th e m inerals, it m ust be m entioned th a t m ost of the ores m ined in the K atan g a are th e carbonates m alachite,

[C

u

(OH)2. C

u

C 0 3], and azurite,

[Cu(OH)2. 2Cu C 0 3],

and the silicate chrysocolla. This mineral is of indefinite composition, being really a m etacolloid, or perhaps a solid solution of dioptase in gelatinous silica.

There are lesser am ounts of the following m inerals also p re s e n t:—-

D ioptase . [CuSi04.H 20]

S k e t c h S e c t io n o f F u n g u r u m e J>y GVO 1919

Note The beds o f th e M in e s e rie s are try the ir, norma/ sequence

P ro b a b le re p e titio n o f b e d s J>y T h ru stin g ( This section was ontu seen

from a d ista n ce bur is suggested by Van Ooornincks fie ld Map)

N o r t h South

* * / / / / y y * /

N°r,h

/ ¿ y

,

^Note The beds o f the M in e series

O m T _____ ¿dd_J have been overturned

S k e tc h S e c tio n o f L u /s w /s h i

Fi g. 5 .

342

S h a ttu ck ite [2.CuSi03.H 20 ?]

P lancheite . [2.C uSi03.H 20 ?]

K a tan g ite . P ro b a b ly sim ilar, paler in colour

Plancheite.

There are also still lesser am ounts o f : C uprite . . . [Cu20]

T enorite or M elaconite [CuO].

The rarer m inerals found include :—

T orbernite [C u(U 02)2P 20 8.12H 20 ] and

C ornetite . [(CuOH);iP 0 4].

dip in the beds of th e Mine Series, sulphides are know n to exist, and it is therefore highly b u t probable th a t th e carbonates an d oxides th a n represent a concentration of these oxidized

sulphides in favourable zones. The greater developm ent of carbonate ore in th e Congo th a n in R hodesia, is un d o u b ted ly due to the fact th a t in th e Congo th e p a re n t rocks_are m uch m ore calcareous or dolom itic.

In som e instances th e carbonate ores are n o t found in situ ; th ey have been trans­

p o rted an d deposited in sub-surface loci,

N

/

7

/

T A

K u n d e /u n g u

Tq/c

D o lo m it e

Ta/c

D o lo m ih c Sha/es

^{4 0 0 m}

----

P _ P

cv- --- ' '

J«UQrtzite C'f'des

Sehest

5 K e t c h P l a n o f i u K u n i

( A f t e r M R t c h e t )

( S o m e w h a t s im p lifie d

)

The M in e is h e m p w o rd e d by b o fh O pencast o n d Unde rg ro u nd methods

The beds o f the M in e S e n e s o re o v e rtu rn e d

Fi g. 6 .

In certain of th e mines, n o tab ly Chinkolobwe and T uushia, various ores of the radioactive elem ents are found : P itc h ­ blende (U raninite), B ecquerelite, Soddite, Curite, Schoepite, G um m ite.

Commonly associated w ith copper m inerals th ere are a num ber of cobalt m inerals am ong which m ay be m en tio n ed :—

Cobalt oxide : P ro b ab ly a com posite product, including various cobalt oxide m inerals.

P erh ap s Asbolite.

L innaeite : [Co:,S4‘.

C arrollite : [Co,Cu S4].

These are some of th e ores w hich are being w orked a t th e presen t tim e.

I t has alread y been m entioned th a t down

where stru c tu ra l conditions were right for an im pounding of supergene solutions. An exam ple of th is is th e new ly found orebody a t K am bove. M ost of th e Congo deposits, however, rep resen t concentrations of car­

bonates in th e beds of th e Mine Series down dip. T he enrichm ent en tails a loss of copper from u p p er portions of th e beds, and a move­

m en t of these values down to an horizon which was defined by th e level of th e water- tab le in p a st and present tim es.

As pointed o u t b y F. W . C larke,1 the copper carbonates m ay have been form ed in two w ays— (a) b y th e action of carbonated w aters on copper com pounds, or (b) by the

1 D ata o f Geochemistry, 1924, p. 679.