T h e Mining Magazine
M a naging Director and E d ito r : W . F. W h i t e . A ssista n ts : St. J. R . C. S h e p h e r d , A .R .S.M ., D .I.C ., F.G .S. ; F . H i g h a m , A .R .S.M ., M .Sc., F.G .S.
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Vol. XLI1. No. 2. L O N D O N , F E B R U A R Y , 1930.
ONE SHILLINGPRICEC O N T E N T S
Ed i t o r i a l
N otes ... 66
U ganda Cassiterite ; S kinner’s Mining Y ear Book ; Im p erial College H ostel ; M ineralogy a t Cambridge ; Progress of Tin Restriction ; A T ran satlan tic M onster ; B ritish Steel O u tp u t in 1929 ; Lena Goldfields ; Professor Lawn Elected P resid en t of the In stitu tio n of M ining an d M etallurgy.
T rad e C onditions... 67
The position a t th e en d of 1929 is exam ined.
T he In stitu tio n M e e tin g ... 68
An account is here given of papers presented a t the J a n u a ry In stitu tio n m eeting.
Mining Laws
A paper read before the Royal Society of A rts by Mr.
G ilbert Stone is discussed.
Re v i e w o f Mi n i n g...
69 70
Ar t i c l e sGeology and Mineral Resources of Sierra Leone . . . . Dr. N . R . Junner T he V olum etric E stim ation of Lead
by the Chrom ate Method
J . E. Clennett
Deep Dredging in Malaya
F . G. Payne
The au th o r describes special problem s associated w ith the design of a dredge- for winning tin-concentrates from deep-lying alluvial deposits.
Le t t e r s t o t h e Ed i t o r
Chalcocite in
N .Rhodesia
A . C. Skerl
Placing of Test Bores
Gordon Marriott Bo o k Re v i e w s
M a n tell’s " T in , its M ining, P ro d u c tio n , T echnology a n d A p p lica tio n s ”
D r. S ydney IV. S m ith H a a lc k ’s “ Die G ra v im etrisch en V erfah ren d er an g ew a n d ten G eophysik " H . Shaw G m elin ’s " H a n d b u c h d e r a n o rg an isch en
C hem ie ” D r. M . S. Fisher
W illis’ " Geologie S tru c tu re s ”
H . B . M iln e r Ne w s Le t t e r s
Johannesburg ... 95
Huge Profit from S tate D iggings; Accum ulation oi D iam o n d s; 412 Tons of G o ld ; Increasing Lives of Mines ; Em erald Mining Results.
2—3
87
91 91
91 92 93 94
F o rt Jam eson, N. Rhodesia ...
G reat E a st Road ; Salisbury-B lantyre R oad ; B lantyre- F o rt Jam eson R oad ; Tete-D edza R oad ; Tete- F o rt Jam eson Road ; D istances ; G eneral Rem arks ; Railroad Construction ; Customs Union ; N ative Labour.
B r is b a n e ...
Queensland Mining Legislation ; The Coal Stoppage ; The Mount Isa E n terp rise ; The Lawn Hills V enture ; Anglo-Persian Oil Company and P ap u a ; Geophysical Prospecting.
V ancouver...
New Power Project ; P ortland Canal ; Anyox ; The K ootenays ; W eather.
Toronto ...
Gold P roduction of O ntario ; Porcupine ; K irkland Lake ; Sudbury D is tr ic t; R ouyn ; P atricia D istrict ; M anitoba.
PA G E
96
C a m b o rn e ...
Tin Restriction ; South C rofty and Geevor ; Wheal R eeth ; U nem ploym ent ; Dolcoath.
Pe r s o n a l
73
Tr a d e Pa r a g r a p h s82
98
100 102
104
10 5 105 Me t a l Ma r k e t s ...107
St a t i s t i c s o f Pr o d u c t i o n...109
Pr i c e s o f Ch e m i c a l s... I l l Sh a r e Qu o t a t i o n s... 11 2 Mi n i n g Di g e s tD ev elo p m en ts in M illing P ra c tic e on th e F a r E a s t R a n d
J . L . W illey and S. E . T . E w in g 113 T h e G eology of N o rth e rn R h o d esia (con
tin u e d from th e J a n u a ry issue, p. 47) J ■ A . B ancroft and R . A . Pelletier 117 B u c k e t D redge P ra c tic e in M alay a
E . J . Vallentine 120 M an g an ese D ep o sits on th e Gold C oast
D . W . B ish o p p and W . J . H ughes 123 Influence of W olfram on T in-S lags
K . V. Christie and E . O. Jones 125 Sh o r t No t i c e s ...
126
Re c e n t Pa t e n t s Pu b l i s h e d ...127
Ne w Bo o k s, Pa m p h l e t s, e t c...127
Co m p a n y Re p o r t s ... 12 8 B atu Caves Tin D re d g in g ; Jo s Tin A rea (Nigeria) ; N orthern T avoy Tin D re d g in g ; R an tau Tin D re d g in g ; Sungei Way- Dredging.Di v i d e n d s De c l a r e d...
128
Ne w Co m p a n i e s Re g i s t e r e d... 12 865
E D I T O R I A L
I N th e issue of th e
M a g a z i n efor N ovem ber an e x tra c t was given of a re p o rt on cassiterite deposits in U ganda, th e a u th o r of which was Mr. A. D. Combe, of th e U ganda Geological Survey, n o t Mr. E. J.
W ayland, as stated.
I N its forty-fourth year, th a t h a rd y annual S kinner’s “ Mining Y ear Book ” m akes its appearance on th e 18th of this m onth.
T his reference work, invaluable to all associated w ith th e industry, contains the p articu lars of all m ining com panies registered in th is cou n try or known on th e London
m ark et. ___
I N A ugust last th e developm ents regarding th e Im perial College Union and H ostel were n o te d here. I t is now announced th a t, th a n k s to th e generosity of Sir O tto B eit an d th e C ity an d Guilds of London In stitu te , th e new building is to be com pleted to th e full h eight of five storeys. T he College is now assured, in th e course of a y ear or tw o, of a resident population of 120, provided th a t in th e m ean
tim e th e required balance of £13,000 can be raised.
I T has been proposed th a t th e D ep a rtm en t of M ineralogy in Cam bridge U niversity should be replaced by tw o d epartm ents, each w ith its own chair— a D e p artm en t and Chair of C rystallography and a D e p a rt
m ent and Chair of Mineralogy and Petrology, which la tte r should be in closest possible relation w ith th e D e p artm en t of Geology.
I t is urged th a t th e fu tu re developm ent of crystallography lies m ainly in fields bordering upon b o th physics an d chem istry. Few will dispute th a t such is th e case ; y et there are th e strongest possible reasons for m aintaining a close liason betw een th e three studies.
T H E revelation th a t w h at were th o u g h t to be th e bones of a dinosaur near T etuan are in fact nothing m ore th a n th e relics of a hay-m aking m achine belonging to a Spanish farm er who abandoned his p ro p erty in 1917 during th e Riff w ar m arks th e end of yet another ‘ ‘ geological discovery. ’ ’ In spite of th e fact th a t th e original explorers m ade a m istake in believing th e curved iron teeth of th e au tom atic rakes to be th e ribs of a species of th is reptile h ith e rto know n only in th e R ocky M ountains, it is evident th a t th ey were rig h t in giving th eir find a T ran s
atla n tic origin because th e m achine is m arked w ith th e nam e of a well known Canadian m an u factu rer.
I T is encouraging to n o te th a t th e steel production of G reat B rita in in th e past year a t 9,654,700 tons is th e highest, except for the m axim um w ar o u tp u t in 1917. B ut for the fact th a t th e figures for th e m onth of Decem ber fell off considerably there is no doubt th a t th e to ta l w ould have been a record. I t is u n fo rtu n ately n o t possible to speak in such optim istic term s of th e in d u stry as a whole. L ittle foreign com petition was m et w ith, owing to th e dem ands on the C ontinent being in excess of supplies, b u t it is doubtful how long such conditions will prevail, as production in G erm any and F rance is g ettin g ab reast of consum ption and costs are lower in those countries.
F U R T H E R progress has been m ade during th e p a st m o n th in th e direction of restricting tin production, th e ran k s of those to ad o p t th e recom m endation of th e Tin P roducers’ Association having been joined, am ong others, b y th e Osborne Chappel group and the P atin o interests, w hilst N igeria is to reduce its o u tp u t for th e first q u a rte r of th e year by 20 per cent. W hether th e policy of restriction will give th e relief an tic ip ated rem ains to be seen, th e view held in some q u arters being th a t a very m uch higher price for th e m etal will be necessary in order to counterbalance th e effect on earnings of th e reduced ou tp u t.
66
T H E position of th e L ena Goldfields, to w hich reference was m ade in the Ja n u a ry issue, w ould appear to have gone from b a d to worse during th e p a st m onth.
Alleging delay in th e p ay m en t of th e wages of th e workers, action was ta k en against the com pany, which was fined 25,000 roubles, its representative a t th e sam e tim e being sentenced to eight m o n th s’ com pulsory labour.
N otice has also been given for th e cancellation of th e agreem ent betw een th e G overnm ent and th e concessionaire. A lthough th e sentence of com pulsory labour on th e com pany’s repre
sentative has since been rem itted , recent events indicate th a t agreem ents w ith the Soviet G overnm ent are not too secure.
U nder th e circum stances those contem plating th e acceptance of appointm ents in R ussia will doubtless appreciate th a t th ey ru n a g reat deal of risk.
P R O FE SSO R J.G .L A W N has been elected
President of th e In stitu tio n of M ining
and M etallurgy for th e coming y ear a n d he
will take office a t th e annual general m eeting, to be held in Ju n e instead of May on account of th e South African congress. Professor Law n was educated a t the R oyal School of Mines and, after early practice and teaching experience in Cum berland, was appointed in 1893 assistant to Sir Clement Le Neve F oster a t South K ensington. Three years later he became Principal and Professor of Mining a t th e South A frican School of Mines, Kim berley. A fter leaving academic life for a tim e to work as assistan t consultant to th e Johannesburg Consolidated In v e st
m ent Com pany, he retu rn ed to it when he was m ade H ead of th e Mining D ep artm en t at Camborne. In th e m eantim e th e South African School, after th e Boer W ar, h ad re
moved to Johannesburg, and there Professor Lawn returned to his form er position in 1909. He definitely tu rn ed his back on teaching, however, only a short year later, when he was appointed Consulting Engineer to the Johannesburg group w ith w hich he had been previously associated, a position he has held to this day, in South Africa and in London. He is the a u th o r of a stan d ard text-book of mine accounting. W hen Professor T ruscott becam e P resident we said of him th a t he was fitly called a scholarly practitioner. Of this y e a r’s president-elect m ay we say th a t he is a practical academ ician.
T ra d e C o n d itio n s
The annual m eetings of th e leading banks are invariably anticipated w ith much interest ; this year the pronouncem ents of the chairm en were aw aited not only w ith interest b u t some m easure of anxiety.
U nder the circum stances it is, therefore, satisfactory to learn th a t th eir sum m ary of the present position is n o t unfavourable and th a t the future is not devoid of encourage
m ent, although there is need for caution.
Few years have w itnessed more factors calculated to disturb business th an 1929.
General elections, w hatever the result m ay be, are never welcome features and in addition the year witnessed serious in te r
national as well as home troubles. T h a t the country should have come through th e try in g times experienced as well as it has is cause for congratulation.
W hether due to th e advent of a Labour G overnm ent or not, it is significant th a t d u rin g 1929 there were no serious trade d isp u tes involving protracted stoppages of
work and this doubtless explains the im provem ent recorded in m ost of the industries of th e country, B oard of Trade figures showing increased production in m an y industries, including non-ferrous m etals, iron and steel, and engineering. T h at this should be th e case is certainly gratifying, in view of th e m any discouraging influences w ith w hich th e country h ad to contend, one of the chief of which was dear money. If no great progress was made, there was no retrogression and the general tren d was upward. W hether the m ovem ent in this direction is to continue seems to depend very largely on provision of further capital for the installation of new m achinery, in order to bring processes up to d ate and enable the industries concerned to com pete success
fully in th e m arkets of the world. As has been rightly pointed out, it is not the province of th e banks to provide t h i s ; their function is to furnish m oney for their custom ers’ current needs. Capital for per
m anent investm ent has to come from the individual and some doubt is felt, in view of th e present high cost of living and heavy taxation, w hether there is a sufficient sum available from this source to m eet the demand.
As was only to be expected, reference was m ade a t m ost of the m eetings to the dis
turbing influences which during th e p ast few m onths have so seriously affected th e com
m ercial life of the country, due to the in
ordinate desire of some people to m ake money quickly, and the hope was expressed th a t this would prove to be only a tem porary aberra
tion from the high traditions of financial and commercial m orality on which not only those a t home b u t those abroad have in the past been accustom ed to rely. In dealing w ith this subject the President of the Society of Incorporated A ccountants and A uditors a t Liverpool last m onth advocated a drastic am endm ent of the com pany law and of Stock Exchange rules in order to restore the confidence of th e public and referred particularly to the irregularities associated w ith the form ation of in te r
locking companies and to the necessity of re-introducing th e Stock Exchange rule as to dealing in vendor shares. I t is satis
factory to learn th a t the la tte r is likely to
receive atten tio n in the near future and it is
to be hoped further am endm ents of th e
Companies A cts to m eet th e abuses which
have recently been so prom inently before
us will not be long delayed.
T h e In stitu tio n M e e tin g
A t th e J a n u a ry m eeting of th e In s titu tio n tw o papers of a widely differing n a tu re were presented—th e first, “ A C ontribution to th e Geology of th e M anganese Ore- deposits in th e Gold Coast Colony and in A sh an ti,” b y Messrs. D. W. B ishopp an d W. J. H u g h e s ; th e second, “ The Influence of W olfram on th e ‘ Combined Tin ’ C ontent of Slags produced in the Sm elting of C assiterite,” b y Messrs. K. V.
Christie and E. O. Jones. The au th o rs were n o t a t th e m eeting, th e first paper being presented b y Mr. J. Allen Howe an d th e second b y Dr. Sydney W. Sm ith. In th is connexion it is to be reg retted th a t of late years m an y papers have been su b m itted in th e absence of th e authors. W hen th e y are ab ro ad th is is, of course, unavoidable, b u t w hen th e au th o rs are in th is co u n try it is surely desirable th a t th e y should sponsor th e ir own work. The best-intentioned d e p u ty finds it difficult to im p a rt th a t conviction w ith which th e a u th o r himself would presen t his chosen them e.
P rio r to th e in tro d u ctio n of th e subjects before th e m eeting, th e President spoke of th e decline in th e num ber of papers presented for discussion a t the In stitu tio n m eetings. As he rem arked, m an y which form erly w ould have been received from overseas are now presented to th e local societies. In these circum stances there is evidently some justification for th e con
ten tio n th a t it would be b e tte r if only one com m unication were accepted for discussion each evening, especially as alm ost invariably, w hen tw o papers are presented, only th e first receives due a tte n tio n . W ith the plea for m ore papers we are ourselves in sy m p a th y and there is certain ly m uch to be said for th e suggestion th a t th e younger an d perhaps less experienced m em bers of th e profession should be encouraged to come forw ard w ith th eir theses, discussion of which b y th e older m em bers would be beneficial to both. There is, however, another aspect of th is m a tte r. I t is well know n th a t some m ining com panies, w ittingly or otherwise, place obstacles in th e w ay of th e publication of papers b y th e ir officials, b u t this difficulty would n o t be experienced if it were m ore generally realized how m uch th e engineer benefits, and in tu rn th e com
p an y w ith w hich he is associated, by the free discussion of his work.
To rev ert to th e papers, th e m anganese deposits of th e Gold Coast Colony, discovered in May,
1 9 1 4 ,by th e D irector of th e Geological Survey, cam e in to prom inence during th e W ar, w hen those of th e Caucasus were cut off and shipping difficulties curtailed th e supplies from In d ia a n d Brazil. W ork during th is period of a c tiv ity was described in th e
Ma g a z i n efor D ecem ber,
1 9 1 7 ,by Mr. Stanley H. F ord. T he pap er of Messrs.
B ishopp an d H ughes, w hich will be found sum m arized elsewhere in th is issue, con
ta in e d a detailed account of th e deposits of th e In s u ta are a an d th is p a rt of th e ir com m unication appears to be th e m ost valuable, as allowance should be m ade for th e fact th a t th e a u th o rs w ould probably have been p rep ared slightly to a lte r their regional geology h a d th e y been in possession of th e provisional geological m ap of th e Gold Coast an d W estern Togoland, w hich was only recently published. T he w ork of the au th o rs has, however, th e stam p of th o ro u g h ness and, in spite of th e difficulties of the co u n try an d th e d esirab ility for more evidence, th e y have realized th a t in com
m ercial geological work, as indeed in any geological work, it is useless to m ake a plan in w hich a series of outcrops are left “ hanging in th e a ir.” In th e conduct of such work th e utm o st possible use m u st be m ade of tim e sp en t in th e field, b u t in th e office an intelligent in terp re ta tio n of th e collected d a ta is advisable as it is possible th a t if the in te rp re ta tio n is n o t form ed b y th e geologist him self someone less capable will have no hesitatio n in jum ping to desired conclusions.
C ontributions to th e discussion of this pap er were m ade by Sir A lbert K itson, Mr. H. K. S cott, Mr. J . H. Goodchild, and Professor C. G. Cullis.
The w ork of Messrs. C hristie an d Jones was in itia te d by a consideration of the penalties im posed by a tin-sm elting com pany in th e S tra its for th e presence of sm all qu an tities of tu n g stic oxide in tin con
centrates. T he a u th o rs’ line of a tta c k m ay be judged from th e sum m ary of their paper, w hich will be found elsewhere.
I t was p o in ted o u t in discussion th a t the w ork was entirely on a la b o ra to ry scale, b u t th e results o b tain ed are nevertheless extrem ely useful. Dr. S m ith gave the discussion a good send-off a n d useful con
trib u tio n s were m ade by D r. W. R. Jones
an d th e President.
M in in g L aw s
In April, 1927, Mr. G ilbert Stone read a paper on m ining law before th e In s titu tion which was subsequently presented a t the Second E m pire Mining and M etallurgical Congress in Canada, b u t pressure of other im portant m a tte r a t th e tim e prevented more th a n a bare reference to th e subject in the
Ma g a z i n efor May of th a t year.
The presentation by the same au th o r of a paper, which is in th e n atu re of a sequel, before th e R oyal Society of A rts on Ja n u a ry 22 affords an o p p o rtu n ity for exam ining a m a tte r which does not often present itself as a subject for discussion among mining men. In his first paper Mr. Stone illum inated a num ber of aspects of the subject which tended to show, inter alia, the inter-dependence of the m ineral develop
ment of a country an d its wise adm inistration and m ade a plea for the rem oval of un certainties as to th e ownership of rights to minerals, w hether of the royal or base metals, and also for th e intensive prospecting of sparsely-populated Crown lands.
The au th o r introduced his present thesis by reference to an am using anom aly. As is well known, m any present-day legal codes are founded on th e original Rom an law and y et the fram ing of th is law was substantially affected by a q u ain t belief current in those tim es th a t m inerals grow and th a t a mine left alone long enough would be found to have replenished itself.
Such a belief is com parable to the native Malayan conception of th e grow th of tin ore to which Mr. Scrivenor has so enter
tainingly alluded in his book “ A Sketch of Malayan M ining.” So far from m inerals replenishing them selves, however, th ey m ust be regarded as w asting assets which once exhausted are lost. Moreover, th ey are essentially indigenous and belong to the country in which th ey are found and it is the d u ty of a Governm ent to tak e care of the w ealth th a t is b u t m ay cease to be.
Mr. Stone adum brates several specific reforms which, in his position as legal consultant to th e Advisory Council on Minerals of th e Im perial In stitu te, will com m and respect. These deal w ith the rights of th e prospector and of the miner, the need for th e encouragem ent of both and of capital, th e surety and length of title, the size of areas and term s of grant, and rents and royalties. His exam ination of each separate contention invests it with added interest and he m akes it clear th a t
the aim has been, not only th a t of bringing into conform ity th e m ining regulations of the Em pire, b u t also th e encouragem ent of active m ineral discovery an d develop
m ent by the rem oval of existing onerous conditions.
One im p o rtan t point which emerges more th a n once from th is paper, and one which will be generally endorsed, is th a t it m atters not th e n atio n ality of the prospector nor th e country of origin of th e developm ent syndicate, except perhaps for reasons of sentim ent. The foreigner who is assisting in th e discovery and m ining of n a tu ra l resources is adding to the w ealth of th a t country. In cases of emergency it is m erely a m a tte r of legislation to ensure th a t no m ineral products are rem oved to alien countries. I t is well to rem em ber also in this as in other connexions th a t the chief gain to th e S tate of th e exploitation of mineral w ealth lies, not in th e fees, rents, and royalties received, b u t in th e work done, the developm ent effected, the industries thereby created, th e labour employed, and the m oney circulated.
On the subject of th e general question of prospecting and title, a prospecting syndicate which is com m itted to a large capital outlay of a very speculative n atu re in a region of w hich th e geology is com
paratively or quite unknown expects more favourable treatm en t in th e m a tte r of concessions th a n those who come later to exploit w hat has been m ade m anifest, and provision ought to be m ade accordingly.
In contradistinction to this, as th e stage of production approaches th e area licensed should ten d to diminish, b u t it is less generally appreciated th a t th e owners of such producing areas should have indefinite powers to expand in a direction which will enable them to w ork a proved ore-body.
The legal com m ittee to which Mr. Stone acts in an advisory capacity is one in which resides a considerable power to benefit th e m ining engineer operating in the Dominions and Colonies. The personnel of this com m ittee is one to commend itself.
I t is questionable, however, w hether
sufficient weight is always attach ed to its
representations by some authorities overseas,
though it is believed th a t th e Colonial Office
is fully aware of th e value of th e advice th a t
has in th e p ast been given and some overseas
Governm ents have adopted its views and
expressed their appreciation of the assistance
rendered.
R E V I E W O F M I N I N G
In tr o d u c tio n .—W ith th e price of tin
continuing uncertain and the copper m ark et in such a condition th a t prices seem to be artificially supported, th e p a st m o n th has been som ew hat dull. A m inor boom in R hodesian copper shares has ta k en place on th e news of high bore-hole values from the N ’Changa w estern extension. T rade con
ditions should be b etter, as th e B ank ra te has been lowered from 5% to 4J% .
T r a n s v a a l.—The o u tp u t of gold on th e
R an d during J a n u a ry was 848,245 oz. and in outside districts 34,556 oz., m aking a to ta l of 882,801 oz., as com pared w ith 851,134 oz. in December. A t th e end of J a n u a ry the num ber of natives working a t th e gold m ines was 190,663, as com pared w ith 184,280 a t th e end of December.
The retu rn s of th e R a n d C ham ber of Mines show th a t m ore th a n 31,000,000 tons of ore was m illed during 1929, an increase of 446,000 tons on th e previous year, and th e gold obtained was 10,414,000 oz., an increase of 55,470 oz. W orking costs a t 19s. lOd. per to n show a decrease of Id . per ton, b u t th e revenue was 3d. per to n lower.
W orking profit was down £122,000 a t
£12,908,191 and dividends a t £8,413,616 were £45,000 lower.
T he G overnm ent of N orthern R hodesia is sta te d to have advised th e G overnm ent of th e U nion th a t recruiting of N orthern n atives for w ork on th e R an d m ines will not be welcomed, as all available labour is needed for th e developm ent of th e copper fields. I t is probable th a t th e authorities concerned will be forced to abandon re c ru it
m ent in R hodesia and th e Union is re
opening negotiations w ith th e Portuguese G overnm ent in order to obtain labour from Mozambique.
In th e last issue of th e
Ma g a z i n ethe adoption of an agreem ent betw een the R obinson Deep an d th e Village Deep was announced. I t is now sta te d th a t th e G overnm ent of th e Union, exercising its powers under th e Gold Law, will appoint a Commission to investigate th e proposed am algam ation.
S o u th e r n R h o d e sia .—The o u tp u t of
gold during Decem ber was 46,829 oz., as com pared w ith 46,219 oz. in N ovem ber and 44,772 oz. in Decem ber, 1928. O ther o u t
p u ts in Decem ber were : Silver, 6,694 oz. ; copper, 180 t o n s ; coal, 111,885 tons ; chrome ore, 28,206 t o n s ; asbestos, 3,971
tons ; m ica, 13 to n s ; diam onds, 9 carats.
The to ta l o u tp u t of gold for 1929 was 560,813 oz., as com pared w ith 576,113 oz.
th e year before, and th e to ta l m ineral production was valued a t £4,871,774, as against £4,448,311 in 1928.
In J u ly la st it was announced th a t developm ents a t th e S ham va Mines h a d been unfavourable an d th a t th e fu tu re depended on th e results of w ork u n d e rtak en on th e recom m endation of Dr. Malcolm M aclaren. This has been so discouraging th a t developm ent operations have been discontinued. The poor results are due ap p a re n tly to th e fact th a t th e ore-bearing channels have become so wide th a t th e ground can no longer be profitably tre a te d for its gold c o n ten t. The w ork done h as shown t h a t th ere are no indications of an y co n tractio n in these w idths an d it is in ten d ed to close down the m ine after crushing an d tre a tin g th e payable ore available.
The M ayfair m ine has been compelled, by th e failure of a suction-gas engine, to cease milling. D evelopm ent w ork w ill be carried on pending th e replacem ent of the engine, w hich it is expected will be com pleted in ab o u t six m onths.
S outhern R hodesia B ase M etals C orpora
tion has inform ed its shareholders th a t the option to purchase 75,000 of th e unissued
£1 shares of th e corporation, w hich was g ra n ted to th e R io T in to C om pany, has not been exercised.
The ore reserves of th e Globe a n d Phoenix mine a t th e end of 1929 are estim ated at
100,500 tons, containing 115,600 oz. of gold, representing an increase of 14,300 tons as com pared w ith th e end of th e previous year.
N o r th e r n R h o d e s ia .— Shareholders of
th e R hodesian Congo B order Concession have heen inform ed of resu lts from th ree bore
holes situ a ted in th e “ New D isc o v e ry ” area of th e N ’Changa Copper Mines. Bore-hole N .E . 16 has c u t th e w estern extension of the
“ D am bo ” lode a t a d ep th of 285 ft. and from 285 ft. to 300 ft. was in ore averaging 3'26% copper. A t 330 ft. an o th er ore- horizon was encountered a n d from 330 ft.
to 355 ft. th e copper c o n ten t averaged
13'04% . Bore-hole N .E . 8 is placed more
centrally betw een th e o u ter lim bs of the
N ’C hanga fold. T his hole en tered an ore-
horizon a t 1,270 ft. an d was rep o rted to be
still in ore a t 1,363 ft., th e 93 ft. of ground
averaging 1 1 0 5 % copper. Bore-hole N .E .
70
10, situ ated about J mile N.W . of th e last hole, encountered ore a t 1,160 ft. and a t 1,170 ft. was still in payable ground, th e 10 ft.
averaging 5'56% copper. The results to d ate on the w estern extension of the N ’Changa property a n d on th e Chingola property seem to indicate th a t copper-values increase tow ards th e west. D evelopm ent w ork has been continued on th e m ain vertical shaft, which is situ ate d on th e R iver Lode, and which a t December 31 last had reached 634 ft. A t this point sinking has been suspended, pending th e installation of further power plant.
Rhodesian Selection T ru st has issued prelim inary results from bore-hole No. 28 on the M ufulira property. This hole, situ ated betw een bore-holes Nos. 7 and 15, has shown th a t a section through these three holes shows an average thickness of 98'6 ft. of m ineralized ground averaging 8'88% copper. B aluba bore-hole No. 10, beginning a t a depth of 796 ft., has passed through 5’8 ft. of ground averaging 4'83%
copper.
G old C o a st.— In th e annual report of the
A shanti Goldfields Corporation th e ore reserves a t th e end of th e financial year—
Septem ber 30 la st—are estim ated a t 590,200 tons, of an average value of 25-2 dw t., an increase of 40,800 tons in q u a n tity an d 1 dw t.
in value for th e year. The blocks of ore in A shanti, Ayeinm, and Ju stic e ’s mines are a t present classed as “ unpayable ” and are not included in th e reserves. D uring th e year 108,007 tons of ore was tre a te d and yielded 118,095 oz. of fine gold and 6,570 oz. of silver. In addition 41 oz. of gold was recovered from sundry sources. T he to ta l recovery averaged 21-88 dw t. per ton and th e m etallurgical p lan t gave a theoretical ex trac
tion of 92-7%. Im provem ents on th e plan t are not y et com pleted, b u t m uch larger tonnages can now be handled. There was a n et profit for th e year of £203,584 and
£162,500 was d istrib u ted as dividends, equal to 65% .
N ig er ia . -The fall in the price of tin
has induced th e Governm ent to reduce rents on m ining leases from 5s. to Is. per acre and on m ining rights from £1 to 4s.
per 100 yd., w hilst all labour obligations have been suspended for six m onths.
A u s tr a lia .—A t th e last annual m eeting
of th e W iluna Gold Corporation it was in tim ated th a t additional capital would be required to bring th e com pany to th e pro
ducing stage. I t is now announced th a t
th e Federal G overnm ent of A ustralia and th e W estern A ustralian G overnm ent have expressed their willingness to guarantee the provision of £300,000 for th is purpose.
D evelopm ents a t th e Lake View and S tar continue to be favourable. I t is now stated th a t in cross-cutting east on th e 3,260 ft.
level of th e Golden Horse-shoe section a t a point 368 ft. south of th e shaft ore assaying 65s. per to n over 7 ft. has been disclosed.
I t is also stated th a t th e rich telluride ore disclosed west of the south drive on th e 300 ft.
level in th e Lake View section has been driven on for 26 ft. The ore has been con
sistently rich, assaying in places 30 oz. per to n over 54 in.
The first section of th e p la n t to tre a t th e Golden' Horseshoe tailings dum p, estim ated a t 2 \ million tons, value 7s. lOd.
per ton, was due to be com pleted a t the beginning of F eb ru ary and th e second section is expected to be ready a t th e beginning of March. E ach section is designed to deal w ith 20,000 tons a m onth.
A circular issued by Federation Tin Mines states th a t negotiations are in progress for th e provision of th e funds required to com plete th e mill. So far this has only been working a t one-third of its capacity and losses have been incurred. W ith th e full p la n t in operation it is calculated th a t it will be possible to work a t a profit w ith tin a t its present price. I t is also proposed to extend th e redem ption period of the debentures for a further five years. Recent developm ents on th e Fowler and D unn lode are sta te d to have exposed ore averaging 6% over 3 ft.
M a la y a .—Shareholders of the Taiping
Tin D redging Com pany are inform ed th a t it has been decided to acquire 40 acres of area “ A ” o u t of the 121 acres selected by Mr. Mungo P ark. This area of 40 acres is estim ated to contain 2,366,000 cu. yd. of ground averaging 0'4 k a tty per cu. yd. By their agreem ent w ith th e G overnm ent th e purchasers m ay move th e electric tra n s mission line which traverses th e “ A ” and
“ B ” areas an d re-erect it on a m utually agreed site. A rea “ B ” is gradually being acquired as th e option agreem ents expire.
This area contains 210 acres selected for
dredging w hich are estim ated to contain
13,950,000 cu. yd. of ground averaging
0-628 k a tty per cu. yd. N egotiations are
proceeding w ith th e South T aiping Company
for th e purchase of their dredge, which has a
capacity of 130,000 cu. yd. per m onth.
72
A progress rep o rt issued by K am par M alaya Tin D redging shows th a t during th e th ree m onths ended Decem ber 31 last 672,000 cu. yd. of ground was tre a te d yielding 239 to n s of tin concentrates. I t was originally estim ated th a t 150,000 cu. yd.
of ground w ould be tre a te d per m onth, recovering 58 tons of concentrates. I t is also s ta te d th a t w orking costs have been reduced to 3 |d . per cu. yd., which is equivalent to
£45 per to n of concentrates.
C o r n w a ll.—W heal R eeth has been forced
to close down owing to th e fall in th e price in tin . T he com pany is endeavouring to raise fresh capital, as it is desired to double th e capacity of th e existing mill.
U n ite d S ta te s.— The effort of th e copper
producers in th e U n ited S tates to hold the price of th e m e ta l a t 18 cents per lb. is probably responsible for th e closing down of certain of the M ontana copper mines. So far three m ines have been closed down an d other employees of th e A naconda Com pany have been placed on p a rt tim e. I t will be recalled th a t in th e U n ited S tates an agreem ent exists w ith th e in terested unions by which wages v a ry w ith th e selling price of copper.
P a n a m a .—A progress rep o rt issued by
P an a m a C orporation, L td ., contains encouraging results. The value of th e Sabalo R iver deposits has been confirmed a n d prospecting operations are being actively continued in th e D arien Concession.
The upper tunnel of th e H atillos district, Mina B lanca, has now been driven for 541 ft.
on th e lode. L ead an d gold values are persistent. T he lower tunnel is now 1,597 ft.
long and has also been driven entirely in ore. On P an am a No. 1 th e 4th level has been driven 2,000 ft. under th e m ain ore- body and a series of cross-cuts m ade a t the extrem e end of the tunnel have disclosed an ore-body 29 in. wide, w ith an average value of £4 8s. per ton. W ork has recom m enced on th e 6th level and a t a dep th of
4 6 7ft. th e lode is 72 in. wide and assays
£5 5s. per ton.
M e x ic o .—The annual report of th e San
Francisco Mines of Mexico shows th e estim ated ore reserves a t Septem ber
3 0last to be
1 ,4 5 8 ,9 0 0tons of ore fully blocked out and
4 3 5 ,6 0 0to n s p a rtly blocked out, as com pared w ith
1 ,1 9 4 ,0 0 0tons and
3 4 9 ,0 0 0tons respectively a t th e end of the previous year. The sulphide ore averages
8 T 7 %lead,
1 0 '3 3 %zinc,
0 ’7 %copper, and
2 3 0gms. silver and
0 ’8 7gm. gold per
ton. T he ore m illed was 307,450 tons, as com pared w ith 300,010 to n s th e y ear before.
The net profit for th e year was £333,589, out of which dividends am ounting to 3s. 9d.
p er share were paid, th e ra te being 3 7 j% . T here was a shortage of power during th e y ear an d a 1,800 k.w. steam -driven electric power p la n t was erected, coming in to opera
tion on D ecem ber 1 last.
J a p a n .—The last rep o rt of th e Chosen
C orporation show ed th a t owing to th e em bargo placed b y th e Jap an ese G overn
m en t on th e export of gold it was n o t always possible for th e corporation to o b tain the b est price for its products. T he raising of th e em bargo on J a n u a ry 11 was followed by th e first shipm ent of gold on J a n u a ry 21.
D iam onds.—
T he yearly rep o rt of Messrs.
J. K. Sm it an d Zonen contains in terestin g inform ation on sm all crystalline diam onds.
As an effort to co u n teract th e rising price of carbons, th e use of sm all cry stals for diam ond drilling purposes has been developed. By th e new m ethod a drill-crow n read y for use can be supplied a t half th e price of a single carbon and it is calculated th a t th e large saving in cost is n o t offset b y loss of drilling efficiency.
The production of alluvial diam onds in th e T ran sv aal during 1929 was 1,046,802 carats, valued a t £2,587,741, or 96,500 carats less th a n in th e previous year.
T he rep o rt of th e De Beers Consolidated for th e year ended Ju n e 30 last p o in ts out th a t, while accounts do n o t reveal any im provem ent in th e com pany’s diam ond sales during th e year, th ere has been evidence of a gradual absorption of stocks which have accum ulated in th e han d s of th e trade.
T he absorption has been m ade possible by th e g reatly reduced o u tp u t from alluvial fields and should im prove th e sta te of the diam ond m ark et. D uring th e y e ar no m ining was done a t th e De Beers or K im berley mines, b u t 4,720,776 loads of blue ground, averaging app ro x im ately 0'23 carat per load, was hoisted from the W esselton, B ultfontein, and D utoitspan mines.
A circular to shareholders of th e Con
solidated D iam ond Mines of South-W est A frica states th a t prospecting on the m arine terraces in th e area n o rth of the Orange R iver in th e Sperrgebiet is pro
ceeding favourably. W ork has shown th a t
th e diam ond-bearing terrace has a length of
20 miles and it is estim ated th a t th e reserves
are 1,750,000 carats.
SIERRA LEONE
By N. R. J U N N E R , D.Sc., D.I.C., M.I.M.M.
Director of the Geological
In t r o d u c t o r y.—Sierra Leone
isth e oldest of th e B ritish W est African Crown Colonies.
I t comprises th e Colony, having an area of 250 square miles, and th e P ro tecto rate 27,000 square miles. The Colony was founded in 1787 as a perm anent settlem ent for freed slaves, and in 1808 the Crown took over com plete control. The P rotectorate was proclaim ed in 1896. I t is bounded on the north-w est, north, and north-east sides by French Guinea, and on the south-east by Liberia.
Survey of Sierra Leone
and its beautiful surroundings, is th e m ain port and principal tow n and it is th e head
qu arters of th e G overnm ent. B onthe is th e second port. The G overnm ent railw ay, 2 ft. 6 in. gauge, provides th e chief m eans of com m unication w ith th e P rotectorate. The m ain line from Freetow n to P endem bu is 227 miles long, an d th e branch line from B auya to K am abai is 104 miles long. At th e present tim e there are about 500 miles of m otor roads. These are m ainly feeder roads to th e railw ay. The G overnm ent is actively
Gr a n i t e Hi l l s
The w hite population is about 1,000 and the to ta l African population is a little over 1,500,000. The density of the population— 57 per square mile— is slightly greater th an th a t of Nigeria, and alm ost three tim es as great as th a t of th e Gold Coast.
The A frican population of th e Colony consists largely of “ C reoles” English- speaking descendants of th e original settlers.
The dom inant tribes of th e P ro tecto rate are Mendes, Temnes, Lim bas, Sherbros, Konnos, Korankos, Susus, Kissis, Lokos, and Y alunkas. F or th e m ost p a rt these tribes are pagans, b u t in certain districts, for exam ple, P o rt Loko, K am bia, and Karene, m any of them have adopted the M ohammedan religion.
Freetow n w ith its fine n a tu ra l harbour 73
n e a r Ka m a b a i.
engaged in th e construction of pioneer roads, and by th e end of 1930 there will be nearly 1,000 miles of roads fit for m otor transport.
The chief exports from Sierra Leone are palm kernels and palm oil. These comprise about 60% of th e to ta l ann u al value of th e exports, and are th e chief source of revenue to th e G overnm ent. In consequence the prosperity of Sierra Leone is largely influenced by th e price of these products.
K ola nuts, ginger, and piassava ra n k next in th e list of exports. Cocoa, coffee, and coco
n u ts are grown in certain districts, b u t they have n o t y e t become im p o rtan t exports.
Rice is th e principal food crop of th e natives and b o th hill rice an d swam p rice are grown on an extensive scale.
The la titu d e of Sierra Leone ranges from
74
6° 55' N. to 10° N. The clim ate is tropical w ith a heavy rainfall an d high atm ospheric h um idity. In th e plateau area of th e h in te r
land th e h u m id ity is less th a n n ear th e coast and th e clim ate is b etter.
There is a single rain y season lasting from ab o u t th e end of May to th e end of October.
N ear th e coast ab o u t 75% of th e annual rain falls during th e period J u n e to Septem ber, b u t inland th e season is longer.
The rain y season is preceded, and followed, by a period of thunderstorm s. T he average rainfall over th e whole of th e co u n try is more th a n 100 in. per annum , and it decreases gradually from ab o u t 140-150 in. on th e coast to ab o u t 90 in. a t K abala. Records kept a t Freetow n show th a t a m arked reduction in th e rainfall has tak en place during th e last 40 years.
In general th e m axim um range of shade tem p eratu re is from 70° to 95°, b u t from Decem ber to F eb ru a ry or M arch th e
“ h a rm a tta n ” — a dry w ind coming from th e N .N .E .—blows and th e days are h otter, and th e nights cooler, th a n usual.
Ph y s i o g r a p h i c Fe a t u r e s.
—The principal physiographic divisions of th e cou n try are as follows :—
(1) T he m ountainous peninsula of the Colony.
(2) The coastal belt.
(3) T he inland p lateau x and m ountains.
(1) T he Colony m ountains consist of a com plex of basic igneous rocks (gabbros, norites, etc.) elongated roughly parallel to th e coast line. The m ountains rise a b ru p tly from th e sea to an elevation of about 3,000 ft.
They are th ick ly wooded and well w atered, th e average rainfall being betw een 150 and 200 in.
(2) The coastal belt extends inland for a distance up to 100 miles from th e coast.
I t is relatively flat, an d rises gradually from sea level to ab o u t 500 ft. a t th e foot of th e scarp m arking th e edge of th e p lateau region. Isolated hills, and ranges of hills, rise from th e plain. The coastal m argin is low-lying and th e chief rivers are tid al for m any miles from th e sea.
(3) The n orth-eastern portion of th e P ro tec to rate is an elevated p la tea u and m ountainous region, th e bulk of which is betw een 1,000 and 2,000 ft. above sea level.
R ising above th is are other p lateau x and m ountain ranges. The m ost im p o rta n t of these up lan d areas are as follows :—
(a)
T he Lom a m ountains, consisting of a prom inent g ranite plateau nearly 200
square miles in area a n d ab o u t 5,000 ft.
above sea level. Several peaks rise above th is level. B intum ane w ith an a ltitu d e of ab o u t 6,000 ft. is th e highest of these peaks.
(b) The T em bikunda highlands, a t the source of th e N iger R iver, consisting of a granite plateau, w ith a general a ltitu d e of betw een 2,000 ft. and 3,000 ft., surm ounted by num erous peaks and m o u n tain s rising to above 4,000 ft. Sankan Biraw a, w ith an a ltitu d e of n early 6,000 ft., is th e h ig h est of these peaks.
The N iger R iver has its source in th is p lateau on th e A nglo-French b o u n d ary at an elevation determ ined b y aneroid b a ro m eter as ab o u t 2,650 ft. above sea level.
T he Sewa R iver, th e largest riv er in Sierra Leone, an d th e Meli R iv er— a b ran ch of the Moa R iver— also have th e ir source in this plateau.
(c) The K agnari an d Sula m ountains extend in a n o rth and south direction, for a distance of ab o u t 80 miles, from Mongeri (Central Province) to n ear K ondem baia (N orthern Province). T he K ag n ari m oun
ta in s are highly dissected and thickly wooded an d reach an a ltitu d e of nearly 2,000 ft. The Sula m o u n tain s rise to 3,000 ft.
in th e K oinadugu d istric t an d for long distances range from 2,000 ft. to 2,500 ft. in altitu d e. The K agnari an d Sula m ountains are composed of m etam orphosed ancient sedim ents and lavas in tru d e d by granite.
Prom ising prospects of alluvial gold have been found a t several places in stream s draining these rocks. T he K am b u i hills in th e K ennem a an d P an g u m a d istricts of th e C entral Province are com posed of similar rocks to those in th e K ag n ari a n d Sula m ountains. The K am bui hills are continuous w ith th e N im ini m ountains, w hich are com
posed largely of g ran ite w ith patches of schistose rocks.
(d) T he Saionya or T alla p lateau (Karene
D istrict, N o rth ern Province). T his is p art of th e extensive F u ta J a lo n highlands of the neighbouring p a rt of F rench G uinea. Near Saionya th e p la te a u is bounded b y an escarp
m en t rising a b ru p tly to an altitu d e of about 2,500 ft.
Geology.
The Colony a n d P ro tecto rate of Sierra Leone were geologically exam ined b y D r. F. D ix e y 1 during th e period 1919-21, and as a result of Dr. D ix ey ’s work, an d th a t of th e present Geological
1 T h e G eology of S ie rra L eo n e, Q .J.G .S ., Vol.
lx x x i, p t. 2, 1925, a n d R e p o rts of th e G eological S u rv e y fo r 1919, 1920, a n d 1921.
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Pr o v i s i o n a l Ge o l o g i c a l Ma p o f Si e r r a Le o n e.
Survey, th e broad geological features of the country are m oderately well known, although very little detailed work has been undertaken up to th e present.
A provisional classification of th e m ain geological form ations is given below. The accom panying geological m ap shows the surface distribution of these form ations.
(1) Pleistocene ? Sediments.
(2) Basic Igneous Intrusions.
(3) Saionya Scarp Series.
(4) Rokell R iver Series.
(5) Igneous Intrusions. G ranitic rocks and subordinate basic igneous rocks.
(6) M aram pa Schist Series.
(7) K am bui Schist Series.
(8) Crystalline Schists and Gneisses of the Coastal belt.
The youngest rocks are th e Pleistocene ?
beds—sands and clays w ith, in places, some
lignite—of th e coastal belt. A few m arine
shells of recent ty p e have been found in these
beds near Freetow n, and fragm ents of plan ts
are common locally in th e shales.
7 (i
The nex t rocks, in order of age, are the flat bedded sandstones and shales, w ith in tercalated sills of dolerite, form ing th e Saionya Scarp. D isconnected patches of false-bedded arkose and conglom erate in the K am bia D istrict are probably of th e same age. These beds are p a rt of an extensive form ation, nam ed “ Gres siliceux horizon
ta u x ” by th e F rench geologists. G rapto- lites,1 indicating a Middle Silurian age for th e beds, have been found in shales of the
“ Gres siliceux h o riz o n ta u x ” a t Telimele, F rench Guinea, N.W . of Saionya.
The beds of th e Saionya Scarp Series rest unconform ably on a th ick series of shales,
sandstones, and conglom erates, w ith in te r
calated silicified lavas and ashes, for w hich th e nam e “ Rokell R iver Series ” 2 has been proposed. In general th e rocks of th is series are folded and cleaved, b u t only slightly m etam orphosed. No fossils have been found in th e sedim ents and a p a rt from dykes of dolerite, no igneous rock is know n to intrude the series.
The sedim ents of th e Rokell R iver Series generally form plains covered b y grass and orchard bush, while th e volcanic rocks form hills and low ridges. The sandstones are w ater-bearing and th e p a u city of w ater in th e stream s draining these rocks is a characteristic feature.
1 J . H . S inclair. D isco v ery of S ilu ria n Fossils in F re n c h G uinea, Journal o f Geology, p p . 475-8, 1928.
2 F . D ix ey . T h e G eology of S ierra L eone, Q .J.G .S ., Vol. Ixxxi, p t. 2, 1925, a n d R e p o rt of th e S u rv ey for 1920.
A v ast unconform ity separates th e Rokell R iver Series from th e older igneous and m etam orphic rocks. The sequence of th e m etam orphic rocks is im perfectly known, bu t it is believed th a t th e M aram pa Schist Series is th e youngest, and th a t th e crystalline schists and gneisses of th e coastal belt are th e oldest, of these rocks.
The M aram pa Series is com posed largely of argillaceous phyllites an d sericite-schists, w ith su bordinate q uartz-schists a n d green and black ortho-schists. N um erous small masses of g ran ite in tru d e th e rocks forming, in places, com posite gneisses. T he general tre n d of th e M aram pa schists is between
N. and N.N .W . D ips are usually steep, b u t owing to th e fact th a t th e beds are in places puckered and co ntorted, th e dip varies w idely in directio n and am ount.
In th e K am b u i hills, and in th e Sula and K agnari m ountains, th e prevailing rocks are highly m etam orphosed schists of sedim entary an d igneous origin having a general tren d betw een N .N .E . a n d N .E . The nam e
" K am bui Schists ” is proposed for these rocks. The schists are older th a n th e biotite g ran ite of th e P ro tecto ra te. T hey are also in tru d ed by m uscovite-granite, an d are p e n e trated by tourm aline and m uscovite- pegm atites, an d b y num erous q u a rtz veins and dykes of dolerite. O uartzites, banded ironstones, quartz-schists, an d m ica-schists are th e m ost prom inent rocks of sedim entary origin, and hornblende-schists, talc-schists, am phibolites, serpentine, and chlorite-schists are th e chief igneous types. L im estone and dolom ite are very rare b u t it is possible th a t
Mo u n t Si m b a, No r t h-e a s t Ko n n o.
some of th e am phibolites have been derived from calcareous sedim ents.
D eposits of chrom ite, h em atite, and gold have been found in th e K am bui Schists.
The Crystalline Schists and Gneisses of th e coastal belt form a wide tra c t running roughly parallel to th e coast line. The prevailing rocks are gneisses and granulites rich in hornblende an d garnet. In certain localities pyroxene-granulites and biotite- and graphite-gneisses are prom inently developed.
G ranite is th e m ost ab u n d an t intrusive rock and covers about half of th e
im portance. These are followed by m oderate am ounts of anorthosite, an d sm all volum es of peridotite, and other rocks. The peridotites are unusually rich in FeO and th e y are interm ediate in com position betw een the ord in ary p eridotites and th e unique h ortonolite dunites of th e Bushveld. Dykes of beerbachite, dolerite, and m icropegm atite occur in concentric an d rad ial tension fissures form ed b y th e sagging of th e central portion of th e cooled mass. T itaniferous iron ores (ilm enite and titanom agnetite) form persistent bands on one horizon in th e lower p a rt of the intrusion. Chrom ite is apparently
Se w a Fa l l s— 1 1 0 f t. h i g h—n e a r Pu n d a r u, Ce n t r a l Pr o v i n c e.
Protectorate. The predom inant ty p e is a foliated biotite-granite, b u t hornblende- granite and m uscovite-granite, and syenitic and granodioritic modifications, occur in certain areas. N ear K am abai and Binkolo, and in several other districts, th e granite forms vertically fluted domes and pinnacles rising to as m uch as 2,000 ft. above the surrounding country.
The m ountain m ass of th e Colony of Sierra Leone together w ith th e B anana Islands, is a portion of a very large basin
shaped sheet of basic igneous rocks of uncertain age. The floor of th e intrusion is not visible and the roof rocks have been rem oved by erosion.
The rocks have a stratiform arrangem ent, and th ey show a well defined prim ary banding (fluxion structure).
Olivine gabbro (including olivine-rich troctolite and olivine norite) is the m ost ab u n d an t rock in th e intrusion. O rdinary gabbro and norite are n ex t in order of
rare. D eposits of alluvial platinum have been found in th e Y ork district.
Several other sim ilar basic intrusions and swarms of related dolerite dykes occur close to, and parallel to, th e coast line between French G uinea and Liberia. I t is possible th a t th e fissures in w hich these linear intrusions occur were developed b y crustal m ovem ents connected w ith th e form ation of th e coast line.
Mi n e r a l r e s o u r c e s.
— Prior to th e for
m ation of th e present Geological Survey very
little was known regarding th e m ineral
resources of Sierra Leone. There h ad been
practically no m ining (apart from native
workings for iron ore), and m inerals did not
figure in th e list of exports. No m ineral
deposits of commercial im portance h ad been
found and it was genefally believed th a t the
m ineral resources of th e country were
negligible. D uring th e past three years the
Geological Survey has discovered deposits of
gold, platinum , hem atite, chrom ite, ilm enite,
and other m inerals, and it is believed th a t the exploitation of th e m ineral resources will soon become an im p o rta n t facto r in th e economic developm ent of th e country. Sierra Leone, w ith her g reat p o ten tial w ater-pow er resources, her w aterw ays and fine harbour, and her p ro x im ity to E urope and N orth A m erica, has m an y n a tu ra l advantages and these will m aterially assist in th e developm ent of th e m ineral resources.
Gold.— R ecent w ork b y th e Geological
Survey has shown th a t gold is associated w ith th e K am bui schists of th e K agnari and Sula m o u n tain s over a len g th of ab o u t 90 miles, from th e Seli R iver near K ondem baia
sta te in th e form of sm all nuggets, as large and small p itte d grains, an d as cry stals and dust. Two nuggets— one w eighing 7-4 gram s {4f dwt.) and an o th er weighing 1-66 gram s—
were found by th e w riter in th e bran ch of th e W hale R iver heading from Y ork Pass, an d o th er nuggets up to ab o u t 4 dw t. in size have been found by th e m ining com panies in th e course of prospecting. T he platin u m is associated w ith large q u an tities of ilm enite (see analyses in T able II) an d a little m agne
tite an d sc an ty chrom ite. T he ilm enite is likely to be a valuable by-product of pla tin u m m ining. A n analysis m ade by th e Im p erial In s titu te of th e crude platinum
Fi e l d Ca m p, Sa i o n y a.
(K oinadugu district) on th e n o rth to near Mongeri (M oyamba district) on th e south.
T his w ork was purely of a reconnaissance n atu re, b u t sufficient evidence was obtained to show th a t alluvial gold is w idely d istri
b u te d and th a t th e Sula-K agnari schist-belt is well w orthy of very careful prospecting.
The localities from w hich th e m ost encouraging prospects were obtained are indicated on th e geological m ap accom panying th is paper. Exclusive pro
specting licences for gold covering an area of ab o u t 50 square miles have been applied for in th e neighbourhood of th e P am p an a R iver near M asombiri. Elsew here in Sierra Leone alluvial gold has been found in several localities b u t n o t in encouraging quantities.
P la tin u m .—A lluvial platin u m is widely
d istrib u te d in beach an d stream gravels in th e P eninsula of Sierra Leone and prom ising deposits have been located in th e Y ork d istrict. The platinum occurs in the native
washed from th e Big W ater near Y ork Pass gave th e following result :— P latin u m , 87% ; osm iridium , 1-3% ; palladium , 2-0% ; iron, 9-9% . N o system atic ex am ination of th e rocks for p latin u m has been m ade and th e alluvial p latin u m has n o t y e t been traced to its source.
E xclusive prospecting licences aggregating ab o u t 20 square miles in area have been tak en up for platinum . These licences are now being surveyed an d prospected.
Iro n .— S ierra Leone is v ery rich in iron
