QI 00 I3

KENYA u-S: - :32r-.'~.-':‘.-' :':';';s.;-.; 3 REPCRT No.13 rs. -:::-~ ILA—'-N:~1'¢)1:3.7‘g"3:1l“u:’:f L2: ' RATE. .5! I PO. 8:: 30525 I ' »

- _ -‘ . ' ‘ Ll‘LIYRAKYfllA!’ I. PROTECIOIIATE or KENYA . m min snowmen.Q~~~IGU.n~m-0fllmn '~'~oTzc~oXATEQF’ KENYA -- . ‘DIAIIOIIWAlROml ' ‘ MINING AND.AND. GEOLOGICALGEOLOGICAILDEPARTMENT '

GEOLOGICALGEOLOGICAL ' SURVEYSUBYBY OFOF KENYA'{ENYA .

IIUIIINI ‘“ "IEr-‘-. GEQMDG’

t. MIIIII ANIIII—'—'IIAVII AIIIA IIIN‘IA CIIIIINI (WITH(WITH COLOUREDCOLOURED MAP)hlA?) , by F. . , TLJ. Parkinspn,Parkinson, Sc.D.,Sc,D., M.Inst.M.M.h1.inst.M.M. .

. ‘ . “V (\K\ \30 7r‘ ,;.::.i1..v (K) in- ,vr$ i,:.P;:\.; ' \y,'." '..'...... cQ,!k::, , , .' . L'''. . ;,,,a .t . ..d\\ - ; '' '..-..:'i~9 - ' II I' . 1 ~45.- I """‘-'~«': mm” ' 1I...... i :;7711‘.i 1 , 43W18f7 . . . ; . 1 “With "w" “W :; 1 . vk,c,, c: :::.-.. \.: k.\ 50B\ . . . . .- Ham“ 5773?..2‘1 ^s:,-! a; C'. I PWO ' F013-For.: ~ ' . . .

...... ,...... >* ...... jji,Y ...... ,:~&i.i'pb.fac.. . . i947i93i ‘' _ MEDmDBYBY THETHE GOVERNMENTGOVERNMENT PRINTERPRJFR . . NAIROBINAIROBI 4 . - PricePri& Sh.Sh. 2'2. CONTENTS IPAGF. I-PRELIMINANY:lnuLIMINAuv; Plryriogrnpliy.Pliyaiogrnphy. Dr;ti.nugc,Drainage, thcthe TaitPTfliNl Hills. CommunicalionsCommunications .-- . lI—OUTLINEOUTLINE OF Gmux;~;GEOLOGY,’ Sequence and Stratigraphic Table,Table. ,&e,Age, Structure; Distribution ofOf Basement System Sediments in Kenya ...... 111-THEIII—THE ORTHO-GNEISSESOnTHO-GNEIssEs AND THEIRTHEIII A~'OCIATIONASSOCIATION WITH HORNBLENDE-SCHISTSHORNBLENOE-SCHISTS

IV-THElV—THE PARA-GNEISSES-PARA-GNEISSES— ' . (1) General . . ,. .. . . -...... (2) Para-GneissesPara Gneisses Associated with Mzima Argillaceous Schists. Right BapkBank of River Tsavo ...... 10 (3) Para-GneissesPara-Gneisses occurring in the Central Part of the Tsavo Traverse . . ll . . (4) The Maktau Hills ...... 12 (5) Graphitic Gneisses, Athi River ...... 12

' V-THEV—THE PARA-SCHISTS AND ASSOCIATEDROTKS-Rocxs— . (”The(1)The Mzima Bend Section ...... (2) PetrographyPctrography of the Rocks of the Mzima Bend and the Loosoito Range . 13 (a)The Quartzites~uartzites ...... ll (b) Kyanite—quartzKyanite-quartz Schists ...... 15 (c) Kyanite-Kyanite-graphitegraphite Schists ...... 15> (4(a') Rocks of doubtful origin, akin to hornt'elshornfe!? ...... 16 ' (3) The Volcanic Sub-GroupSub-Group ...... II: (4)The schistSchist Series near Mgange, northiwestnorth-west of the Taita -HillsHills .. III (a)in) Quartzites . . . . -...... - Is. (6)(b) Graphite-Kyanite-SchistsGraphite-Kyanite~5chists . . . . ,...... (c)Compact Graphitic Rocks with Garnet ."i ., ...... 19 (d) Actinolite. Schists ...... ,.. .' . . 20 (5)The Crystalline ~imesionesLimestones .... ' ...... - .. ‘ .. ,K . . 2I VI—COMPOSITEVI--COMPOSITEGNEISS&GNEISSES OF THE TAITA HILLSHILLS‘ . . ,...... 21. VII-SUMMARYVii—SUMMARY OF0F GEOLOGICALCONCLUSIONS ...... ,.,- . . . . 23 VlVIII-ECONOMICH—ECONQMIC MINERALS ...... a _ ...... '23 lX—REFERENCESIX-REFZRENCES ...... 24

APPENDICES [--Graphitel—Graphite Deposits, Tsavo ...... 24 11-Kyamteil—Kyan-ite Deposits, Murka ...... , ...... 29 111-Magnesitelli—Magnesite Deposits, Kinyiki ...... 31 IV--OtherlV—Other Mineralhlincral Deposits at Kinyiki—Asbestos,Kinyiki-Asbestos, Quartz.Quartz, FelsparFelspar, Vernliculite.Vermiculite, Corundum and Sapphire.Sapphire Miscellaneous Minerals ...... _ .

.V-MicaV—Mica ...... ‘1'.) VI-MiscellaneousVl—Miscellaneous Minerals—~Limestone,Minerals-Limestone. Clays. Rose Quartz, Cappcr, Copper, Kaolin, Minerals of the Taita Hill ...... '33,

ADDENDUM Mineral ProductiOn Production Figures subsequent to the Report . . i.' . . ..as . . 40 FOREWORD The name of DrDr. Parkinson will need no introduction to East AfricanAfrican. geologists;geologists- he may justifiablyjustifiably be called the doyen of thoscthose who have worked inIn East Africa during the last thirty years or more. He began the work that led to the present report in June. 1940, whenwhen he made a detailed examination of deposits on the western flankflank of Kinyiki Hi1l:nearHill.’near' Mtito Andei. Subsequently he mapped extensiveextensive portions of the country south of Mtito Andei. paying particular attention to the Tsavo valley and the Taita Hills. and returning to Kinyiki when underground exploration was begun there. , The survey continued untiltlntil May. 1940. when Dr. Parkinson returned to Nairobi to : carry out petrographicalpctrographical and other work. Soon after. he was unfortunately taken ill. and after hurriedly completing his report and map. he was compelled to resign his appointment. As the period during which the survey continued waswas, insufinsufficientficient to .allowallow a complete examination of the area, a small amount of data gathered by earlier officialofficial observers has been added to Dr. Parkinson's map. In addition, several appendices have ’ been written to describe inIn more detail the mineral deposits, particularly the inteccstinginteresting suite OFof rocks and minerals found at Kinyiki Hill. - The work carried out by Dr. Parkinson and the prospector who worked witwhimwithfihim waSwas financedfinanced by a grant from the Colonial Development Fund.

WILLIAM PULFREY, " . Senior Ger~fegi.rr.Gent'agirl. Nairobi, February; 1946. CONTENTS—(Cami)

LIST OF ILLUSTRATLONSILLUSTRATIONS , PAGEFilo: FRONTISPIECE-NpuliaFRONTISPIECEHNQUHR 11ll and Kitchwa ya Tembo, Tsavo Valley, looking West.west. . Text Fig. Il interprets thcthe profileprofile sccnseen in this photograph. FIG. I-Sectionl—Section of Kitchwa ya Tembo, showing mode of thrusting along the

Tsavo Valley ,!...... ,\,- 5 FIG. 2-Diagrammatic2—Diagrammatic section oE"theof the suggested roof-pendantroof—pendant of Basement System'System" ?. :' 6 Sedimentary Rocks ...... 6 r; FIG.3-Brecciation3—Brecciation of hornblende schist by microcline gneiss, below railway ,:' bridge, Mtito Andei ...... IS FIG.4--Intrusions4—Intrusions of biotite-gneiss and pegmatites.pegmatites Meruga Road,Road. near Yale, , Taita Hills ... . ‘ ...... \ .\ . . .. '21 FIG. 5--Section5—Section at the west end of the Merugahleruga RoadRoad. Taita Hills,Hills. showing the ?{if composite nature of the gneisses ... . , ...... ,F 22 3; ILLUSTRATIONS IN APPENDICES FtG.F~G.6-Graphite6~Graphite deposits, Tsavo ...... ‘_' 25 FIG. 7--Geological7—Geological map of Kinyiki Hill, near .MtitoMtito Andei . . facing page 32 . 4 MAP ' ' i . Preliminary geological mapmap. of the Mtito-Andei-TsavoMtito-Andei~Tsavo area; .scalescale I1: :25Q;000--in.250,000—in end folder. OUTLINES OF THE GEOLOGY OF THE MTITO . . ANDEI—TSAVOANDEI-TSAVO AREA I—PRELIMINARYI-PRELIMINARY PHYSIOGRAPHY TakenTaken asas'aa whole, the district, over 2,000 square miles in extent, coveredcovercd by the . :. -..-i~csnce“nicsance survey lies tolo the west of the railway from froni Mtito Andei to Voi. and extends westwards to the Chyulu .RangeRange andnntl the eastern slopes of KilimanjaroKilimanjaro. ThereThcre are no mapsniaps of this area which can justly be said to be accurate within a mile. TheTllc Taita Hills must be looked uponup011 as a geographical entity, and a reasonably accurate sketch-map was prepared on a scale of 1:62.5001 :62,500 and approximately correct form-lines inserted. The country is closely populated and fruit and vegetables are growngown for the Mombasa market, under the guidance'of guidance 'of thethe Agricultural Station at Wundanyi.

. The area consists of a plain sloping gradually to the south-south-east, broken by '' sharply rising hills with a tendency south of the River Tsavo to a linear arrangement. _’ Volcanic rocks overlie the gneisses ol'of the southern partyofpart of thethe Yatta Plateau (elevatmn(elevation about 3,000 ft.) and in the Chyulu Range to the west (6.000(6,000 toto 7,000 ft.).

With the exception of the TaitaTzita Hills to the south and the neighbourhood of thethe ,, Voi-Taveta railway, the cou‘ntry‘iscotintry is uninhabited and practically waterless;waterless: a desolate expanse ofoC thorn-scrub and occasional flflat-toppedat-tapped acacias.atacias. In addition to the lavalava plateaux mentioned, outliers from the Kilimanjaro association ofoC flflowsows and puys occur as isolated remnants in' the neighbourhood of the upper reaches of the Tsavo and along the Mzima River. Besides the peneplain forming the “"floorfloor level" of the area, traces of.aof a second appears just discernible along the sides of the hills north of Voi and on the western flflanksanks of the Taita Hills, but levellinglevelling must be done before this can be consideredconsidercd as established. . DRAINAGE Apart from the Athi River, which does not matetially ininfluencefluence the physiography of the area under consideration, drainage is eeffectedfiected normally by the Tsavo River alone. such tributariestributaries as exist being dry except thethe Mzima on thethe northern bank and thethe headwaters on thethe lowerlower slopes of Kilimanjaro, which do not inin themselvesthemselves ininflucnccfluence thethe area. No tributarytributary entering on thethe southern bank carries water, except as occasional freshets.freshets. These broad sandysandy channels, rarelyrarely contained between high banks but.but occupying shallow grooves, are thethe “Laks”"Laks" or “Luggas”"Luggas" of thethe Northern Frontier.Frontier District, a convincing witness here as therethere to to the the heavy rainfall of thethe past. The greater part at leastleast of thethe Mgange Lak, which traversestraverses the the thorn-scrub thorn-scrub country fromfrom itsits source in-in thethe Taita Hills for some 20 miles north to~theto.the Tsavo River, has, as farfar as itit isis possible toto judgejudge by appearances, been dry for a numbernumtjer of years. The country is,is, in in fact,fact, rapidlyrapidly approaching thethe semi-desert state throughthrough which thethe Northern Frontier isis now passing on itsits way toto a complete stagestap of desolation. 0nOn thethe other , hand, thethe channel north of Mtito Andei Station a fewfew years ago contained fl flowingowing 8 water for some months, at least,least, of thethe year. it It isis now apparently uniformly drydry. Water holes, small and more or lessless precarious inin existence and duration,duration,.arcare foundfound at various and rarerare intervalsintervals and formform a meagre supply for animal life.life. TheThe'TaitaTaita Hills must be takentaken as an exception toto.thothe destitution elsewhere universal inin thethe area,area. and itit isis therethere and along thethe Taveta-Voi Branch Railway thatthat any human beings are found, a factfact not wholly accounted forfor by thethe eastern boundary of thethe .GameGame Reserve running near thethe edge of thethe hill country as far south as the Tsavo. The Tsavo River, forfor twelvetwelve toto fififteenfteen miles up- up-stream-stream fromfrom the the railway, runsruns inin a general direction across thethe grain of thethe rocks, rocks, which Is is characteristically constant a fewfew degrees west of north.‘north.. ItIt thenthen enters a stretch between Ngulia and Rhodesian Hill where, owing toto aa marked change of dip, itit approximates toto a strike streamstream.

'Along'Along thethe 90 miles stretch south of Marsabit inin thethe Northern Frontier~ronlierDistrict where similarsimilar rocksrocks arearc well exposedexposed thethe strikestrike variesvaries onlyonly slightlyslightly fromfrom aa northnorth andand southsouth direction. L2

Passing westwards,westwards. bcyondbeyond the entrance of the Mzima by a small waterfall.waterfall. !hethe diminishing Tsavoflaw is Toun

i inIn order to facilitate the work of the survey, rough tracks for ears'werecars were made-—made- «tn-n...-

- (a)lo) along the Tsavo Valley, .. -.. . (I)(1) from Signaller‘sSign?ller's CampCanip to RefugeeRefugce Camp,Canip, 2|21 miles (thence 18 miles to the Taveta-Voi road), - ’ ' ...... I1 (2) SignallcrsSignaller's Camp to Tsavo Railway Bridge,tJn'dgc, 35-}354 miles.milcs. . .. (In)(h) fromTtonr MIIktItuMaktnu (3,(3,607607 rmTI.) to:a Mgangc CampCnmp (2890(2,890 it.)ft.) I21}I2f. miles in Ita directtlirfkt line. and, (c) Mgange Camp to Kedai Sisal Estate (2,600 ft.)ft.),. about 8 miles. Additions were also mademade'toto thettie southerniouthern end of the road connecting Signaller's . Camp on thethe left bank of the Tsavo to Mtito Andei Station.Station.. . -- -- These routes together with the p~n~i~aL_s!ream.s~ofthe Taita HilIsL.were sut~]red--.-.--. by prismatic compasscompass. range fifindernder and tape. In this work I1 have to acknowledge substantialsubsfan'tial help from Mr. B. A. Brannstrom. ' -. .... ~ .. ‘ IT—OUTLINEIT-OUTLINE OF GEOLOGY SequenceSeqlrerlce andnrld StratigraphjcS~ra~igropl!ic Table.—TheTable.-The sequence established is given inin thethc .*: tabulation below. ItI1 must be regarded as largely eonjeeturalconjectural. ,....,, " ......

. s. 5 : PleistocenePleistocerle and.ar~d.Recent.Recer~r. ‘ ‘ - ~ . ‘.... = . . AIIIIviuIn.—DepositsAlllrvium.-Deposits of red sandy earth of considerableconiiderable depthdeprwhichwhich form a ' large proportion of the flflatat and slightly undulating ground covered with thornthorn . . ' trees and spare vegetation between the more hilly regions. WideWide, fl flatat valleys of sandy clay are thethe .equivalentequivalent of the "mbugas"‘mbugas" of Tanganyika Territory. . 7Lower7 Lower Pleistocene.Plcisrocerte. Basalts.—NotBosa1ts.-Not discussed in this report. Portions of the area examined which ' are covered by basalt are, however, shown on the map... ' '- Age Unknown.Unknowrr. Dunite.Durlbe.-An—An intrusive boss to the north of Mtito Andei~ndeiStation. Not~dttouchedtouched on here. . .

Arc/meanA rcl~aean(Basement(Basermnr System).Sysrer~~). . .. I Pegmatitcs.Pegmorires. and scatteredscattered exposures of ortho-microcline-gneiss typicallytypically associated with hornblende-schists which forfor thethe greater part are'are. regardedregarded asas ' intrusive.intrusive. The second felsparfelspar of thethe gneiss isis usually albite or.or, albite-oligoclase. ArgillaceousArgillaceolu SedimentarySedir~rerrtarySeries . . Crystalline Limestones. Kyanite-Sehists.KyaniteSchists. . . ,, Graphite-Schism,Graphite-Schists, and schists containing both kyanite and graphite or either as dominant minerals.

Muscovite-Muscovite-' and Biotite-Schists, including migmatites of the Taita HillsHills. , Gamet-Sehists,Garnet-Schists, .Pyroxene-Garnet-Schists,Pyroxene-Garnet-Schists, etc.etc ' Quartz-Schists.QuartzSchists, ferriferous,ferriferous, garnetit'erous garnetiferous and kyanitiferous. "Volcanic Group". A series of epidote-epidote-hornblcnde-schistshornblende-schists with seapolite. scapolite. and garnets. ArenaceousArer~aceo,rsSediIIIentaryScdirrlentary Sericur~eric.r.-~andsiones—Sandstones and arkosesa;koses which have under-under-,- gone»ggnel penetration soaking. With themthem may occur beds of almost 'unalteredhaltered quartzite, . whiewhich have undergone littlelittle metamorphismn~efamorphismbeyondbiyond: thethe quartzite or quartz-schist , stage. . stage.. AGE . , _ ,, The Archaean rocksrocks ireare believed toto be of approximatelynpproximptely thethe same age as thethe Turoka Series of thethe Magadi Branch Railway and thethe Suk Hills, as judgedjudged by lithologicallithological characterscharacters, association and degree of metamorphism. They form part of thethe Basement System of Kenya, and correspond with WhatChat has beenbeqn called thethe Lower Basement ComplexComplex inin. Tanganyika, which hashas beenbeen describeddescribed (Grantham(Grantham'ei.et al.at. 19401940. p. l8)18) asas distinguisheddistinguished byby thethe presencepresence of normal sediments, sediments, thethe occurrenceoccrlrrence of crystalline crystalline 5

(C)(0it1t isis worthy of remark,remark, thatthat thethe conspicuousconspicuous low low fiflat-toppedat-topped hill of Kangetchwa, ' of somewhatsomewhat circular shape shape andand about fourfour miles in diameter, isis composed."composed of aa microcline gneissgneiss andand other rockscharacteristicrocks characteristic of thethe para-gneisspara-gneiss group-5group and isis situatedsituated due due southsouth of Ngulia.Npulia. (See(See p.p. 9). Owing toto transporttransport andg‘ and ' other difdifficulties,ficulties, a close examination of Kangetchwa and itsits surroundings;surroundings> could not be made but at leastleast the the possibility of itsits representingrcptescnting a klippe:klippe ' should bebc considered.considcrcd. .x

‘_ ' Kitchw’a 8 7(2m . . U ' '

73mm

R.

FIG 1 ,‘ Section of KitchwaKitchwn ya TemboITembo, showing mode of thrustingthri~sting a'ong theIhe Ts1voTsivo Valley.\'alley. 3'

. DtSTRIBUTION OF BASEMENT‘SYSTEM SEDIMENTS IN KENYA The area of deposition of the rocks now under-under consideration, which for con-f:con- venience we may call the Tsavo Basin. is probably connected under the lavas of the;the- Kapiti Plains with the sections already described near Turoka Station on the MagadifMagadi" Branch Railway. (Parkinson, l9l3,1913, p. 534.) If not actually connected. it can be separatedseparated. from itil only by a relatiVelyrelatively narrow barrier. SomeSonic 200 miles to thetlie north is the basinbasin':5; of deposition running south from the neighbourhoodntiglibot~rhoodof Marsabit to‘ to the northern i3 Uaso Nyiro. This north-north-southsouth belt of ancient sediments is buried by lavas to both east}:east 2. and west, but to the north-east Isis probably connected belowelow the .flowsflows with the para-;.para-,; schists of Ajow (where there are also massive quartzit‘es)quartzites) and Buttellu. This we may-mayx name the .LaisamisLaisamis Basin. On the west are the lavas south of Lake Rudolf dIvIdIng.,dividing:{ ,.it,..it. from'from the Basement System rocks forming the Suk and Chemorongi Hills. As far _. as the writer‘swriter's personal observations go, the more southerly basins, Turoka and Tsavo, ii' especially thetlie latter, contain a higher proportion of arenaceous gneisses than the more * . ”northerlyr'northerly:-.With"With these the “slabby"slabby gneiss of Laisamis",Laisamis", half wayway.betweenbetween Archer's PostPost: andand. Marsabit, and similar rocks in the neighbourhood neighbourhood. shouldshotlld be included. (Parkinsonfi (Parkinson, ;~ 1920,!920, pp. 20, 2|21 and references there givcn.)‘given.)* . . .. ' . Thehe close petrological resemblancereseniblance between the rocksrocks of this portiOn portion of ‘ljtheii:.the , Basement System,Systcni, wherever so far studied, indicates not only continuity or approximateapproxirnatc - * continuity of the areas of deposition but similar provenance of elasticclastic materials. -. . f"7 -. . ItIt. is difdifficultficult not to suppose also a similarity,similarity. .practically.practically an identity, in the"the intensity and physical conditions underundcr which the agents of metamorphism andii and , '_metasomatism-metasorptism worked...... =

'During the journey through. through the Northern Frontier ProvinceProvincc in l9l4-15,1914-15, the true character of the arenaceous gneissesgncisscs wasw~snotno1 properly realized. (Parkinson, I920,1920, p. 26). inIn the same way some _-. ofoC.!hethe TurkwalTurkbl Gorge gneisses (Glenday and Parkinson, I926,1926. p. (06)-606).statedstated to be ortho-gneisses may ' prove,provc,.onon further work. work, to be of sedimentary origin...... 5 r, "—

RegionalRegionaLmetamorphism .metamorphism is obvious and,and. taking into account the facts recorded by the.similarity in the history of ..others others working in still more wide-spread localities,*localities,‘ the .similarity in the history of - the rocks covering so much of the central part of the African continent becomes remarkable. It is tempting €0to consider the possibilitypossibility‘that that this .sedimentarysedimentary section of / i /x . . - /'/ - / / ‘5 — \ \ / 5 (‘0’ r \ _, / G \b / so; \‘h0 S x/ 05 13 0" /. 0°0 3o 94,5 ~— o / (‘0 8 Qt) ou / o .i e. \\° / Y“ v0 2)

”I Wit.“.A-“ rm rl‘l“ ‘i‘l '.. :3 ‘mg‘é ‘ ', lei-.i‘l’ld ., *t *t f 1' iii"

- FIG.^ . ~ia~ramlnaticDiagrainmatic seulic~t~section elof tbcthe zl~ggcstcdsuggested roof-pcndantroof-pendant orof H:~semenlBasement SyslclrrSyslcm'Scdimcntary Scdirncnlary HosAs.Rocks. - the Basement System is a gigantic roof pendant of which, speakingspeaking.generally, generally, the central argillaceous heat-affected core, and the surrounding metasomatically alfectedaffected ,arenaceousarenaceous envelope are left eroded for inspection.impection. The necessary huge batholiths,batholiths. acting under essentially identical physical conditions which alone could have attained such - : a resultresultzhave have not been found, at any rate in adequate dimensions. The great bulk of the ’encasing-reservoirencasing. reservoir (with its supposed albite-oligoclase-microcline-quartzalbite~oligoclase-microcline-quartz magma) exceptexcept where it has perforated the roofroot pendant by by protruding tongues, has bechbeen removed by erosion or buried under later seqmentssediments and lavas. . . ’4l - - . In the areas described, all of which except one were personally examined by the writer in the old days of “foot"Coot sctfarr"',safari", this section of the rocks of the Basement System, comprising para-schistspara-schisls and paragneisses having close petrographical affinities,affinities, has been found at intervals from the northern end of the Suk Hills to the Voi-Tavcta - railway, a distance of overoverr400 400 miles, and from the Suk Hills to Buttellu on-theon the west of Eil Wak,Walt, about 300 miles in an approximahapproximate east 'and‘and westWest direction, that is..?veris‘gver an area of 120,000 sq. miles. On the olherother hand no reason exists to showshow‘ thatthat‘the\. the- sedimentary phase of the System stops where the last exposure has been seen. It - scarcely needs saying that a large proportion of this enormous area is buried by lavas, old lake. deposits and alluvium, and that , much of the System remains to be differentlaled.differentiated. Rocks of the Nyanzian and later Pre-cambrian Systems are apparently absent- throughout the area. - *In'ln an earlier paper (Glenday and Parkinson, 1926, p. 609) "deposition“deposition of Ihethe scdimcntsediment in a geosyncliialgeosynclinal area" and that "the tilted and foldcdfolded beds sunk deeply into Lhsthe viwusviscous uprising magma"mag-ma" were suggested. The hypothesis now put forward 'onon fresh data is essentially that formerly sugges~ed.suggested. - 7

Ill—THE111-THE 0RTHO-GNl‘llSSESORTHO-CNEISSES AND THEIR ASSOCIATION WITH . HORNBLENDE-SCHISTSHORNBLENDE-SCI-IISTS At various points along the eastern end of the Tsavo traverse, igneous rocks occur. They are typical hornblende—schists hornblende-schists andacidand acid gneissgnciss associations which exhibitcshibit evidence of brecciation anda'nd assimilation of the basic partner by the more siliceous on a fairly largelargc scale‘scale.* A later section in this report on the Taita Hills describesdcscribes similar relationships. lnIn thethc Tsavo ValleyVallcy at the road bridge hornblende-schists predominate. TheyThcy arearc locally garnetiferousgarnetifcrous and associated with slabby fifinelynely banded gneiss having a general foliation trending 332°332" to 342“.342". A short distance toto thethe west, where thethc traversetraverse roadroad crosses a dry tributary to the river, the brecciation isis clear. Thin quartz-felspar veins indicate considerable permeation of thethe typetype which gives rise to migmatites, while the whole is cut by broad pegmatite veins at rightright angles toto the foliation. Faults with a throw of an inch or two.two. near which now and again minerals show slight bending, indicate that the rock was nearing thethe solid statestatc at thethe timetime of movement. The gneiss (1.94.81.(1.94.SI.107)t107)? intrusiveinlrusivc into thisthis ,associationassociation inin itsits least least contaminated formfornl near the Tsavo Road bridge bridge, is a compact rockrock not necessarilyshowing necessarily showing a‘markeda marked . foliation. it is spotted with smallsn~allnests of biotitc. The thinthin section shows itit toto be largelylargely composed of microcline, which usually exhibits a fi finene microperthitic structure,strilcture, and isis associated with accessory plagioclase (an acid oligoclase). Characteristicall};characteristic all^; thinthin rimsrims or veins of another species of felspar, probably albite, edge the larger crystals or even form borders to grains of quartz. The latter appears as rounded blebs and occasional large grains. Apatite is an accessory. - A second instance (I.91.Sl.l.).(1.91.Sl.l.). of intrusive gneiss'occursgneiss occurs one mile south-east fromfrom thethc Tsavo Road bridge. This is a hard, compact reddish-reddish-brownbrown rockrock, showing faintfaint banding. It contains a large proportion of microcline inin. . addition to an acid plagioelase.plagiorlase. Rare magnetitemagnetite. and zircon areare. accessory minerals. A uniform, massive, medium-grained, dark grey rockrock (I.92.Sl.106),(1.92.S1.106), showing no foliation in the hand specimen, specimen. closelycloscly associated with thethe streaky hornblende-schist group isis exposed at thethe roadroad bridge over thethe Tsavo. ItIt has has thethe appearanceappearance of aa highly contaminated rock.rock. Only one small grain of microclineniicrocline was detected inin thethe slide.slide. The oligoclase isis often only partially twinnedtwinned probablyprobah1.y asas thethe result result of thethe pressure pressure which has produced crush-shadows inin thethe fewfew irregularirregular grains ofo€ quartz. TheThc interestinterest of thethe rockrock lieslies in in thethe ferro-magnesianferro-magnesian minerals which consists of palepale green green augite altering

..-——1— patchily to hornblende, some apparently original hornblende andand irregularirregular platesplates of

“w...” biotite. Magnetite isis a conspicuous accessory constituentconstituent andand apatite andand sphenesphenc occur rarely. Foliation is noticeable in the arrangement of the dark minerals. —,_— rarely Foliation is noticeable in the arrangement of the dark . About 51}5+ miles west of thethe Tsavo railwayrailway bridge thethe track track crossescrosses aa wide tributarytributary . and exposes an excellent section of banded andand gnarledgnarled ortho-gneissesortho-gneisses with pegmatite veins and hornblende-gneiss inclusions.inclusions. The generalgeneral trendtrend of thethe foliationfoliation isis 330'.330". These rocksrocks when traced traced up thisthis side-valley lose lose much of theirtheir conspicuousconspicuous structurestructure and pass intointo hornblende-biotite-gneisses, loc'allywell-bandedloc'ally well-banded or slightly.slightly. contortedcontorted containing thinthiri pegmatite veins and having garnetsgarnets associatedassociated with thethc hornblende. At 81}8+ miles fromfrom thethe bridge, the same relationshiprelationship as as nearnear thethe roadroad bridge itselfitself isis shown. The strike of thethe foliationfoliation isis 336°.336". Again at ll}II+ miles fromfrom thethe bridge in in thethe bedbed of anan importantimportant tributary;tributary,: thethe Mgange LakLak. flfluxionuxion and locallocal gnarling are well seen.seen. The generalgeneral trendtrend of thethe foliationfoliation isis 344'.344". A short distance upstream along thethe dry bedbed thethe brecciation of aa hornblende-schist by an acid ortho-gneiss andand associatedassociated assimiliation areare seenseen, thethe rocksrocks becoming- locallylocally- garnetiferous- as before. ’For*For similar associations inin thethe north and south ofof thethe Northern Frontier District .rcesrc Parkinson.Parkinson, I‘IZU,IYLU, p. 2|.21. fi?Numbersstumbers 1.94.1.94, etc.etc.. referrefer toto specimensspecimens inin thethe museummtlscum ofof thethc MiningMining andand GeologicalGeological Department,Department, Nairobi. SI.51. [07,107, etc..ctc.. referrefer to to thinthin section section numbers.numbers. in$In existingexisting mapsmlps thisthis channelchannel isis mapped asas rising rising closeclose tolo MgangeMgange CampCamp onon thethe NH-WN.-W. flflanksanks of thethc.Tait1Tait-.1 Hills, aa distancedistance totd'thethe TsavoTwvo River ofof nearlynearly 2020. milesmi1es.B.in aa straightstraight line.line.

rmwwm. 9

An extremely good section, showing the effects of intrusion on a rock still plastic, can be seen along the stream bed olof the Mtito AndciAndei- from the road cross.ingcrossing down- stream to the railway bridge and beyond. At the sharp bcndbend of the road just south of this crossing the strike of the gneissgnciss (of almost binary composition) is 24Se,245', and the dip of thcthe foliation to 341".341'. Itit is a massive well-foliated rock (1.150.51.97),(1.1505197), having , coarse felspathic streaks and clots. A thin section shows it to be an ortho-microclinc-ortho-microcline- gneiss, containing small flakesflakes of biotite with olive-green to black pleochroism.pleochroism Two or three small garnets and a few grains of apatite complete the section. Microcline constitutes about 25 per cent of the rock. The remaining felspar has a refractive indexindex_ rarely as high as that of balsam and is probably albite. It is both twinned and untwinned.Untwinned. A closely similar rock (I.l58.S1.116),(i. l58.SI. “6). occurs in the quarry between the road crossing and the railway. It contains about 20 per cent of microcline. A certain amount of zoning ,is shown by the felspar of both specimens.

F9253

4

Near/y

FIG. 3 BrccciatianBrecciation ai.of harnblenbhornblende schist by nlicrocli#microcli+ pnciss,gnciss, bclowbelow railway bddgc.bridge, MlitoMtito Andci.Andei. I At some 100 yards from the road, going dd:wnstream,downstream, the strike hishas changed to 275'.275' , swings more sharply to a more usuglusual direction and at the bridge is 313".313°. This -_ change in strike,. conveniently called a "swirl"“swirl" and containing within itself minor flfltlxionaluxional movements, was noted in one place as'as. swinging fromfrbm 270"270° to 331'Still“ inIn littlclittle over 50 yards. - The basic elemenielement it,in 'lhcthe ;tssuciationassociation appears just below thc road crossing and near the bridge show shows thcthe chnracterisliccharacteristic steps, after marked brecciation.brccciation. of partial assimilation and the beginnings ofol permeation. The intruding veins of acid gneiss.gnciss. frequently at right angles to each other, appear in variotrsvarious shades of grey according--according“ to the quantity of material absorbed. The schist involved in the mixture is presumably the hornblende-schist dcvclopeddeveloped on the west side of Kinyiki Hill. _ The railway ctlllingcutting at Kinyiki Camp at mile 179/617916 on the railway, showsshow. hornblende-schistshornblende—schists with granitoid bands, striking 350"350“ and dipping eastwards at aboui-about~ 65". This association continues to mile 17119,l7l/9, whenWhen the rocks becon?ebecome markedl:markedlj migmatic with'thewith the development of much mica.mi'ca. In any of these instances where igneous rocks appear aloncalone to be concerned, thethL possibility,possibility of sediments now altered almost beyond recogllition,recognition being alsaalso involvelinvolvcl must not be forgotten. They might occur either as inclusions in various stages c

99 .‘

dissociationdissociation oror inin lit-lit-par-lit~par--lit complexes.complexes. ItTt isis impossibleimpossible onon thethe otherother handhand toto concludeconclude <33 thatthat the the structures structures justjust describeddescribed areare duedue toto laterlater additionsadditions ofof magmamagma distinctdistinct fromfrom thethe restrest ofof thethe assemblage.assemblage. TheThe quietquiet permeationpermeation which which give give riserise toto migmatitesmigmatites and and thethe moremore rapidrapid andand energeticenergetic intrusionsintrusions whichwhich givegive rise rise toto brecciationbrccciation andand thethe variousvarious stages stages ofof assimilation.as~imihti~n. occuroccur sideside byby sidesidc andand nono doubtdoubt tooktook placeplace practicallypractically simultaneously. simultaneously. ThereThere isis aa tendencytendency forlor thethe migmatitesmigmatites andand brecciation brecciation gneissesgneisses toto occuroccur onon thethe

easteast andand southsouth ofof thethe area,area, suggestingsuggesting propinquitypropinquity toto thethe edgeedge ofof thethe magmamagma reservoir.reservoir, ”:L,il.‘;af-‘.

oror inin otherother words,words, thatthat they they representrepresent the the productsproducts ofof peripheralperipheral permeation. permeation. In!“ r':.

I‘v—THEIV-THE PARAGNEISSESPARAGNEISSES ..

(l( 1)—G )--& ENENERALmun. i‘i'l'z'utvi» .t‘ much

InTn consideringconsidering thethe originorigin ofof thethe massivemasshe paragneisscsparagneisses whichwhich areare distinctivedistinctive ofof much ..

may}: a.

ofof thethe country,country, greatgreat difdifficultyficulty is is felt,felt, asas elsewhereelsewhere when when dealing dealing withwith similarsimilar rocks, rocks, inin . fix: distinguishingdistinguishing truetrue ortho-gneissesortho-gneisses fromfrom granitizedgranitized sandstonessandstones andand arkoses.‘arkoses.' . MuchMilch ofof thethe uncertaintyuncertainty isis naturallynaturally duedue toto thethc multiplicitymultiplicity ofof stagesstages inin the the processprocess ofof alteration,alteration, fromfrom the the commencementcommencement ofof gaseousgaseous permeation permeation toto oror togethertogetlier withwith actualactual magmatic magmatic intrusion. intrusion. . .. Withwith thisthis processprocess thethe mineralmineral microcline microcline seemsseems possibly possibly to to be be connectedconnected and and itsits presencepresence in in aa rock rock havinghaving sedimentarysedimentary features features isis regardedregarded as as evidenceevidence ofof metasomaticmetasomatic actionaction oror additions.additions. AA fewfew examplesexamples willwill showsllow thethe range range ofof variations.variations. AnAn earlyearly stagestage inin suchsuch alterationalteration maymay possiblypossibly bebe seenseen inin thethe presence presence ofof aa fewfew grainsgrains ofof microclinemicrocline _, inin aa quartzitequartzite containingcontaining albite'albite Inin small small untwinneduntwinned crystals. crystals. TheThe. specimenspecimen (I.(1.13LS1.7)136tSl.7) waswas collectedcollected aboutabout }+ milemile fromfrom MubugoniMubugoni inin thethe direction direction ofof BulutoniBulutoni onon thethe north-narth- easteast fiflankank ofof Ngulia.Ngulia. TheThe quartzquartz grainsgrains areare fairlyfairly equi-dimensional,equi-dimensional, andand average average aboutabout .0l2.012 in.in. long;long; the the microcline,microcline, ofof moremore irregularirregular shape. shape. averagesaverages .038.038 ,in.,in. andand showsshows a a tendencytendency toto aa linear linear arrangement.arrangement. . . AA higherhigher percentagepercentage of of microclinemicrocline scattered scattered sporadically sporadically throughthrough ,thethe .slide,slide, occursoccurs

inin a a rock rock collectedcollected close close atat handhand (SLIM).(S1.114). TheThe quartzquartz isis frequentlyfrequently veryvery irregulaII:irregulao inin '

outlineoutline andand variablevariable Inin size.size. ‘. ..~

NeighbouringNeighbouring specimensspecimens (1.(1.136.Sl.6)l36.Sl.6) fromfrom BulutoniBulutoni water-water-holehole showsshows microclinemicrocline toto F bebe onlyonly anan accessoryaccessory constituentconstituent. AtAt MubugoniMubugoni waterwatcr-liolehole aboutabout twotwo miles miles toto thethe south-south-eastsouth-south-east itit isis thethe principal principal felsparfelspar andand the the preponderatingpreponderating constituent.constituent. ThisThis :“ rockrock (I.(T.162.Sl.122)162.Sl. I22) takentaken fromfrom the the sideside ofof NguliaNgulia contains contains a a fewfew porphyriticporphyritic felsparsfelspars

are almost no ferro- i‘-*"1¥;‘!r.;: howeverhowever andand mustmust bebe consideredconsidered asas igneous.igneous. InIn bothboth rocksrocks therethere are almost no ferro- . magnesian minerals.

magnesian minerals. :56: a

Kangetchwa,Kangetchwa, tenten milesmiles southsouth ofof Ngulia.Ngulia, isis inin partpart composedcomposed of of microcline-gneissmicrocline-gneiss 3.2; g (III.(III.109.Sls.109.Sls. 112,112, .112a)112a) associatedassociated with with ratherrather fifine-grainedne-grained pegmatites.pegmatites. TheThe plagioclase,.plagioclase, , eithereither twinned twinned or6r untwinned,untwinned, isis probablyprobably albite.albite. QuartzQuartz isis conspicuous,conspicuous, andand muscovitemuscovite inin sieve-like sieve-like crystalscrystals anda& locallylocally biotite biotite withwith aa strongstrong pleochroismpleochroism makemake upup thethe restrest ofof thethe rock. rock. Well foliatedfoliated hornblende schists schists areare associatedassociated with with the the gneisses.gneisses. The sharplysharply risingrising hills characterizingcharacterizing thethe eastern eastern half of thethe areaarea fromfrom Mtito Andei toto thethe Taita Hills may be consideredconsidered here. They comprisecomprise a a rockrock seriesseries similarsimilar toto that that characteristic characteristic of thethe Suk Hills. (Glenday(Glenday andand Parkinson, 1926,1926, pp. 591-606.)591606.) The'groupThe group wherein areare includedincluded certaincertain quartzites may bebe bracketed with others toto thethe west asas microcline-a1bite-oligoclasemicrocline-albite-oligoclase paragneissesparagneisses which takentaken asas aa whole occupy aa position inIn thethe seriesseries of considerableconsiderable importance.importance. The followingfollowing have been examinedexamined. (The(The hills areare consideredconsidered in in order roughlyroughly fromfrom north toto south):south):-—

'Recent'Recent publications publications ofof thethe Geological SurveySurvey of Southern Rhodesia containcontain valuablevaluable observationsobservations on thesethese typestypes of gneisses..(See.gneisses. (See, forfor example, Tyndale-Biscoe,Tyndlle-Biscoe, 1940.) A reponreport on thethe geology of thethc Dodoma Area inin TangantTanganyika (Wade(Wade and Oates,Oatu, 1936, p. 23) should also be consulted.cons~ltcd, . . . i . . .10

1.l. Gneiss from the trigonometrical station of Kamboyo south-south-west of Mtito AndciAndei railway station (J.138.51.92).(I. 138.SI.92). Microcline isIs rare, the quartzes large and irregular inIn outlineol~tlinc-andand the main felspar near to albite.albitc. Other minerals are biotite.biotite, white mica, sphcnesphene and magnetite. 2. Gnciss from south'south. of Kenani Station (1.147,148.Sls.94.95).(l.l47,l48.Sls.94.95). The slidcsslides of ‘ these rocks show no microcline. They arcare garnet-gncisacdgurnchgncisscs containing nIt pligioclaseplagioclase . near to oligoclase-andesine.oligoclase-andesine. InJn habit they arcare massive, very well foliatedfoliated. inconspikouslyinconspiCuously to markedly bonded banded and contain a fewfew pegmatite eyes and bands. -

' At the fifirstrst landieIandie south'south of Kenani. the gneisses (1.154.1(1.154.118) 18) also contain no microcline and ferro-magnesianferro magnesian mineralsminerals are scarce. The strike of the foliation is . . isom. 160'. . - . Outcrops near the main road south of Kenani stationStation c~sistconsist of massive hornblende-gneisshornblende--g'neiss having a tendency to exfoliate in slabby fragments together with various biotite gneisses which outcrop at intervals on or near the road as far north as Mtito Andei. The strike of the foliation is 170m:Streaks170°. Streaks of hornblende - aggregates an inch or so thick and quartz-felsparQuartz-[clspar bands whichWhich are often gdrnetiferousgarnetiferous occur in places in these gneisses. . 3. Ngulia consists of massive para-gneisspara-gneiss similar to that forming the long ridge running southward from KarnboyoKamboyo to Rhodesian Hill.

' 4. The hill, a trigonometrical point known as "Bump",”Bump“, 13 miles east-north-easteast-north-east of Kangetchwa consists in part of very basic .hornblende-schist.hornblende-schist. * 5. At the Sisal Estate, Kedai,.Kedai, banded acid gneisses outcrop. in the 'rive!river bed:bed and are cut by rather coarse pegmatites and inter-banded with hornblende-schists.hornblende-schism. A These rocks and those of the hills north-east of the Taita Hills are. placed in the lower portion of the sequence, i.e.ie. in the Arenaceous Series.Series

(2) PARAGNEISSESPARAGNEISSES'. ASSOCIATED WITH , MZIMKMZIMA' ' ARGILLACEOUS SCHISTS RIGHT RANKBANK ' -- , - OF RIVERTSAVO.Tsavo. These rocks form the ground bordering the road leading down to thcthe alluvium of the,the right bank of the TsnvoTsavo about half a mile east of the junction of the Mzima.Mzima - The thickness of the group is of the,orderthe‘order of 2,000 ft. They are markedly slabby.slabby, solid. compact rocks containing only a small proportion of any of the ferro-magnesinnferro~magnesian minerals as small inconspicuous grains. At firstfirst sight, they strongly recall the para- gneisses of the left-left-bankbank of the river eastwards from Signaller'sSignaller’s Camp, differing from - them, however, in that as far as seen they do not contain microcline, which is so characteristic of those para-gneisses. Some are considered to be of igneous origin. In one such rock (Sl.'77)(S1.'77) the principal constituent of the thin section is a felspar. It is slightly kaolinized and usually untwinned.untwinned, or only partially so, and is characteristically - ’albite-oligoclaseilbite-oligoclase or albite. A few irregular grains of magnetite and some fifilmylmy whiteWhite mica~icadeveloped apparently along planes of movement are accessory minerals. The .presencepresence of a ,littlelittle quartz vermiculévermicul6 forms a distinction from the granitoid gneissesgncisses ot'of the eastern part of the traverse. In the hand specimen.specimen plates of muscovite are . - conspicuous on parting planes. 1 On the other hand another sectio~isection (SI.(S1.76) 76) shornshows predominate (very dusty) quartz.quartz and is thought on that account and general appearance to be a para- para-gneiss.gneiss. itIt consists . .of‘of an interlocking mosaic of quartz and felspar, twinned and untwinned,tIntwinned, [hethe latter - in part at least albite. The slide shows qoartiquartz vermiculC.vermiculé. Accessory minerals arearc muscovite, biotite with very strong absorplion,absorption, garnet in small rounded grains, zircon,zircon. and magnetite, the commonest. The quartz shows a tendency to semi-rounded outlines. Other gneisses may be wholly or in part of sedimentary origin and the felsparlelspar ,- .again, at least in part, is albite. (III.lO,Sl.92).(11~.10$1.92). A rock collected about i9 mile to the west of these, may perhaps be.regarded as the almost purely sedimentary end of a series representing gradttationsgraduations from an orthogneiss to a felspathic quartzite. Amongst the grains.ofgrains of quartz (average diameter .01O.l in.) which comprise almost all the rock are some - of water-clear oligoclase abouiabout .03 in. long. They have the appearance of being'n~ouldedbeing moulded ' on to the other constituents and must be of later growth, enclosing for instance, ll

blcbsblebs of quartz. Accessory minerals are cpidotc,epidote, magnetite, apalite,apatite, brown mic2mice and some muscovite, which is in part secondary. It is suggested that this rock shows the cornmcncementcommencement of that permeation which has so materially altered other sediments of the area. Two and three-quarter miles west of Signallcr'sSignaller's Camp on the right bank of thcthe TnnvaTnave sndand (securingace.utting IIIIas an inolotedisolated exposure, it is a wcll-foliated,well-foliated. fine-grained,linc-grained, yellowish rock (111.U.Sl.62)(111.22.Sl.62) which appears rathcrrather laminatedlamlnated withoutwlthout the laminaelamlnae having essentlulessential diffcrtncesdificrences in constitution. The foliation is marked by crystals of two micas. Muscovite occurs in relatively large. ragged.ragged plates ?ndand appears occasionally as an intergrowth giving a vermiculCvermiculé appearance. The biotite has the intense absorption, olive-green to black, which characterizes this mineral in other rocks of the area. The quartz occurs in large elongated grains, and most of the felspar is untwinned and apparently oligoclase. . . This rock, though differingconsiderablydifiering considerably in appearance must be considered as

having a relationship to those just described and those following. -.§‘iusa{;'\§.;;'-.:J

".5-

- - (3){3) PanacustsscsPARAGNBSSESOCCZ~RRINOOccuaamo IN THE CENTRALPART OF THE'THETSAVO TSAVOTUVERSETRAVERSE ParagneissesParagncisses in the central part of the Tsavo Traverse. approximately mid-way between the Tsavo railway bridge and Signaller'sSignaller‘s Bridge. Bridge, may be subdivided into groups according to locality. 1.l. GneisscsGneisses from the left bank of the Tsavo betweenbetwccn Signaller'sSignaller‘s Camp and Kitchwa ya Tembo. Microscopically these gneisses are seen to contain small flakesflakes of hornblende and two micas. They are rather fi fine-grainedne-grained and friable, unlike - the majority of the paragneisses which are essentially hard and contain fesro-ferro- magnesian minerals only rarely. They have a sedimentary habit of Weathering,weatherisg, and the dip, in general terms, is to the north+astnorth-east at about 30".30'. They contain streaks of pegmatitepegmati-te and are closely associated with hornblende-schists. Both appear . . frequently in road sections. . . A specimen from a point 232* miles east of Signaller’sSignaller's Bridge (51.32)(Sl.32) contzinscontains no biotite but flflakesakes of a hornblende which shows a blue-green element in the ,pleochroism.pleochroism. A similar colour distinguishes the mineral in certain gneisses fmm,from ’ Suk (Glenday and Parkinson, 1926. p. 602). Large irregular crystals of quartz.quartz, large crystals of oligoclase, and possibly a little orthoclase are present.present Epidote, sphenesphme

and rarely small apatite crystals are accessory minerals. .

A second specimen (I.l22,Sl.3l)-collected(1.122,Sl.31)~collectedtwo miles east of Signaller'sSignaller‘s Camp, t-EL".-

-p shows the hornblende replaced by biotite, and some 'whitewhite mica which may be

in part secondary. Microcline is present, and the plagioclaseplagioclase'is , is occasionally “1.5:;

s we.

bordered by a felspar of another kind or possesses a core of different composition :ln

to that of the outer zone. These facts, .whichwhich are far from uncommon, arcare ‘<'.‘.~L. mentioned to show that additions (implying soliltionsolution and migrations of felspathiefelspathic :8"-

material) have taken place since the earliercamel stage of consolidation. Other instances 33".!”

are described in their place. I.‘ 2. Gneisses from the Tsavo Valley south-east of Kitchwa ya Tembo.Ternbo. These rocks and those in the following sub-sections may be considered typical of .thethe paragneissesparagncisses of this part of the traverse. Closely similar gneiss occurs at Bulutoni water-hole. They are hard rocks, slabby in habit, brown or white to pink in 'colour, of uniform grain and occasionally containing a few specks of biotite or .,r magnetiten~agnetitc.andand plates of muscovite collected on the plai~esplanes of foliation. A specimen (I.130:(1.130: 9.25)81.25) from the 'river,river, "15IS miles west-south-westwest~south-west Tsavo railway'railway- ;bridge{bridge is a brown weathering fine-grainedfine-grained 'slabbyslabby paragneiss hayinghying mieroclinemicrodine as the dsminantdominant constituent. The plagicolase, whichjswhich.is apparently 'albite.'albite, is frequently bordered by a rim of translucent felspar showing a refractive index less than balsam. No twinning was noticed in this rim. , A second example (1.131; S1.36)3136) on the river [414 miles West-south-Westwut:south-wtst of the Tsavo railway bridge, is a brown weathering slabby'quartzitic-lookingslabby quartzitic-looking micro- Clinecline-'meissgneiss in the fifield.eld. Its outcrops would be continuousCQ~~'~UOUSwith those-those. of thethc 12

gneiss mentioned above were the strike maintained for about 'threethree quarters of a mile. The presence of a large number of rounded detached-looking grains of quartz in it suggest a sedimentary rock. . '~ BetwcenBetween these outcrops and a point about a mile further east there arearc slabby blnrrybinary gnzissesgneisses in an nppnrcntlyapparently horizontal attitude forming a .marked ridge on both banks of the river. Immediately to 'the‘the east there ureare quartz-mlcre.quartz-mlero- cline gneisses (1.132.S1.26,37)(l. 132.SI.26,37) containing twinned and. untwinned albite,'albite,’ and quartz which tends to have globular outlines and is very duqy,dusty, the dust particles being frequently gathered into paraflelparallel lines. There are no phenocrysts.phenOCrysts. A few flakesflakes of very deep grass-green hornblende are an accessory. At aboutAbout a qu;lrterquarter of a mile further to the casteast a tributary enters from the south and contains slabby biotite-gneisses. occasionally garnetiferous, which higher up the lak are associated with slabby hornblende-gneisses and pegmatite bands.

(4) THE MAKTAU HILLS The group of threqthree hills about 2f miles north of Maktau Station on the Voi-Taveta branch railway are composed principally of gneisses, closely related to those of the Taita Hills. They include types varying considerably in degree of coarseness and'and compositioncomposition ranging from hard, rather fine-grained,fine-grained, compact and -uniformuniform rocks _ showing little sign of foliation inIn hand specimens to coarse quartz-felspar ortho-pneissesortho~gneisses '(lIl.106.Sl.98)(III.106.Sl.98) with xenoliths of medium grained more or less banded biotite-schists. The xenoliths occur in various stages of dissolution and absorption. In the fine-grainedfine—grained .

acid end of the series, microcline is fairly common and is associated, as is usually - the case, with an albite-oligoclase .or-or oligoclase. The quartz forms relatively large, .irregular grains, showing incipient crush shadows.,shadows. Brown mica having strong absorption and a little white mica, possibly in part'part secondary, are inconspicuousinconspicuous- ~constituenls.-constituents. Small grains of microcline occur in a second .glide:slide. These rocks are probably para- _ gneisses, whereas those containing xenoliths are certainlycertainty of igneous origin. The more basic part of a banded gneiss examined (III.105;(111.105; S1.123)Sl.l23) is a fine-grainedfine-grained biotite- hornblende-schist. The specimen sectioned contains no microcline, and felspar is represented by an acid plagioclase. Apatite is a COInmOhcommon accessory.accessory.’ _ Microcline gneissesgneissas (III.111.SI.10.5)(lll.lll .Sl.105) occur with other rocks, largely of sedimentary origin, some lenten miles distant from the Maktau Hills, on the north-westnorth-West flanksflanks of the Taita Group. As at the former locality they are associated withwith‘ "pepper‘pepper and salt" types -~ of"of gneiss and thin bands of pegmatoids. A specimtnspecimen about I)14} miles from Mgange Camp — is a medium grained gneiss, the foliation well marked by streaks of ferro-magnesian minerals, principally biotite, having strong pleochroism from greenish-yellow to.to black. .MicroclineMicrocline is an inconspicwusinconspicuous accessory, and oligoclase is the'the‘ second felspar. A few small grains of epidote and rarer apatite are inconspicuous constituents. ’- , (5) GMPIIITIC GNEISSFS, ATHI RIVER A belt'of graphitic gneissesgneissos is developed over a long strike on or near the right bank of the Athi River between the latitudes of Kibwezi and Tsavo.Tsavo.1t It is considered . as an earlier zone of graphite deposition, and with the exception of a graphite gneiss at Kitchwa ya Tembo, its rocks do not resemble the graphite-bearing types of the Argillaceous Group. described on a later page. The strike is approximately.approximately, 336' roughly parallel loto the course of the river and dapositiondeposition along the zone took place at more .. than one period, as several graphite-bearing;graphite-bearing'horizonshorizons were found, the principal about 40 ft. wide. Specimens from near the junction of the Mbululu and Athi are massivemassiVe well-foliatedwell-foliated rocks, often containing small phenocrysts of felspar, the whole sprinkled

plentifully with flakesflakes of graphite. One (1.166.Sl.136)(1.166.5l.136) from this locality consists of a - rather coarse aggregate of quartz and oligoclase (showing a little perthitic intergrowth) and is almost devoid of ferro-magnesian minerals. A rather finer-grainedfiner-grained rock (L167.Sl.137)(.1167.S|. 137) from the same locality contains graphite in the usual flakes,flakes, about .03 in. long, long. having the characteristic rough edges and 'The‘The presence of albite-oligoclascalbite-oligoctase is a possibilty,possibfllty. as a [elsparlelspar occurs having a refrnc~iverefractive index identical with tblthat of balsam. i13 3 . . reclangular{cclangular outline. This rock is one of the very few examined from this district which shows cataclastic structure in the form of a network of tiny veinsvcins of granulated quartz and felspar logcthertogether with strain shadows in the larger crystals. The.The plagioclasep!agioclase is oligoclase,oligociase, faintly and partially twinned in many instances. -,. V-THEV—THE PARA-SCHISTS AND ASSOCIATED ROCKS (I) TueTne MZIMABennBEND S~CTIONSermon The schist arca,area, embracing the Loosoito Range and the Mzima Bend with i~its southerly continuation to Longa-LongaLonga-Longa Hill may be considered first.first. The followingfollowin$ is a slightly generalized section of the rocks exposed along the Mzima Bend, takentakck in apparent descending order from east to west. ' .+. . . 1. Well—foliatedWell-foliated biotite-gneiss. ' I 8’-.= ' 2. PsammiticPsarnrnitic para-gneisseipara-gneisses (Nos.111.3-8;(Nos.111.3-;8 Sls.75-78Sis.75-78 Pegs.Pegs.4391442)439/442) withot;;Without . microcline and with almost no biotite. These are underlain by a thin bed 0.1of epidote-quartzite ($1.143).(3.143). There is then a gap 'atat the nrbugan~buganear the entrance of the Mzima River, where black sandy soil and scattered basalt outcrops are foundfound: Basal!Basalt occurs also at the mouth of the Mzima. .

3. A thin bed of fine-grbinedfine-grained quartzitequartzile (Peg 447.111.10.~!.144),447.III. 10 Si 144), overlying the . "Volcanic“Volcanic Group",Group“, comprising hornblende, epidote and garnetiferous schists. This _groupgroup ,isis correlated with epidote and other schists of "Signaller's“Signaller's Camp" and in the Tsavo Valley east of KitchwaKilchwa ya Tembo. . . 4. Slabby quartz-schists, ferriferousferriferons and garnetiferous and associated with tourmaline and other pegmatites. The locality here is known as "Fortificiations"“Fortifications" (Peg 449). The'I7ie schists overlie fine-grainedfine-grained well-foliatedwell-foliated slightly banded-banded biotite- gneiss. . Gap. 5. Coarse muscovite-pegmatites. . . 6. Small exposure of friable mica-schist. 7. Thin-Thin-beddedbedded quartz-schist with muscovite, including 'bandband of biotite-bio.uito-rich:rich schist. The branch track to Longa-Longa turns south here (Peg 456). .‘g> Gap with lava outcrops along the main track. 8. Thin beds of .marblemarble alternating with dominanPkyanite;schistsdominant‘kyanite-‘sChists and somesome:

mica-schists. Another branch track turns off to the south here. w‘ mica-schists Another branch track turns off to fi

.;I . hu‘

Gap of nearly a mile, followed to the south by: fi

g b‘ 9. Fine-grained micaceous banded schist. About one mile north-north-north-wes$north-west. of this outcrop, along the strike there is a group of laminated quartzites:quartzites;, (III.40.Sls.121,121a).(III.40.815. 121 ,121a). Mica and kyanite-schists,kyanite--schists, garnetiferous muscovite-muscovite-schistsschists formf'ifore a low ridge with occasional hills overlooking flatfiat sandy grouodground as far as the RiverRiver.;, The northern.northern boundary,boundary of the eastern part of this section is the east and west:.west Tsavo Valley fault or thrust. . TII (2) P&OGRAPHYPmOGR/IPHY OF THE ROCKS OF THE Mz1t.f~MZIMA BEND AND THE LOOSOITOLoosorro RANGE ;:. (a) The Q~iartzitcsQrmrlzires .ItIt should be noted at 'thethe outset that thc “Argillaceous"Argillaceous ~roh~l,Group", so-called toto; . distinguish it from the ortho-gneisses and para-granitoidgneisses.para-granitoid gneisses. of the eastern sectionsectton: of the Tsavo traverse, .ncvehhelessnevertheless frequently includes quartzites or quartzose schists'schists ' . containing a noteworthy.proportionnoteworthy proportion of silica. The. principal outcrop of such rocks—‘-rocks-.: -. the LoosoitoLoosoito, Kevas and Murka Hills which together form a broken and isolated strikestrike.:' ridge about ten miles long south of the EthiopianEthioplan Refugee Camp—mayCamp--may be considered:.considered - ''first.first. The hills are built of many varieties of kyanite-schist and quartz-quartz-schist-schist with,with . . considerable variation in the proportion of the two dominant minerals. The strikestrike,i:: running.throughrunning through the three hills, curves slightly from 347'347" at Loosoito to 332' 332" at Kevasi‘:Kevas:::.., and again to 335'335° at Murka. meThe dip is to the east at about 40'40" toto.45'.45.° Like the hills.!hills I at MaktauMaktau, this ridge rises sharply from a sandy scrub-covered plain which gives nono:i . .

. (. 14' geologicalgcologicai information. TheThc quartzitesq~iartzitcsarearc thethc coarsestcoarscst found in' thethc area but +here.where » examinedcxaniint$l arearc not associatedassociatd with conglomerate bands. Typically theythcy weather with a rough almostalniost scoriaeeousscoriaccous Surfacestlrfacc. beddingbdding beingking indicated by differencesdiffercncu in thethc sizessizcs - of the constituentconslit~lcntgmins.grains. It is suggestedst~ggeslcrlthat theythcy werewcrc depositeddcpositcd near the edgecdgc of the basin. Fragments of hornblende-schisthornhlendc-scltbt. locally markedly~norkcdlygarnetil'erous.garnelifcro~u, lielic scatteredscisttcrcd along the western slopes and an exposureexpostirc of thethc parent rock is found about a third of the way up thethc hill. It shows a laminatedlnminatcd streakiness'streakiness of thethe basic andand-acidacid eleémentsel@ents and semi-pegmatoidsemi-pegn~atoideyescycs round 'irhichwhich thethe'folia~ionfoliation of the-thegneissgneiss bend.bcnd. This composite gneiss is considered to bebc probably a sill. Specimens of quartzitesquaitzites or quartz-schistqtiartz-schist of different types were examinedexanlined from the the locality called “Forti"Fortifications"fications about three-quartersthreequartcn of a mile west from the MzimaMzinia River junction. Characteristically.Charactcris~ically,these schistsxhists are well-well-bandedhanded and dark-coloured, and.and , regular alternations of ferriferottsferrilerotrs and quartzoseqttartzose material are common. The presence of red garnet inin some quantity is not rareran and flflakesakes of graphite occur inin severalseveral instances as a minor constituent. The slabby habit is very marked. This quartzite group underlies the so-called “Volcanic"Volcanic Sub-Group"Sub-Grouf mentionedn~entioocdbelow. One or two points are noteworthy, such as thethe extraordinaryeitraordinrry irregular or amoeboid _ shape of thetlie quartzquark crystals which show no elongation along the foliation, wliilewhile the inclusions they contain and the associated garnets are markedly orientated (SI.(S1.60).60). This peculiarity leads to the conclusion thatthat the rock has been subjected tot6 a process akin to annealing,annealing, which allowed of considerable movement in the.the. molecules of the dominant minerals without disturbing the structure impressedimpressed at an earliercarHer period on the other constituents or the inclusions they contain. Other slides,(lll.l:5.51.59)slides. (III.SS.Sl.59) from the same locality show that thethe foliation planes have a tendencytendency to flAowow. round the garnet porphyroblasts in which polysynthetic‘polysynlhetic twinning is evident (e.t'.(c.f. Hacker.Harker. Fig. 1001O11 A. p. 220). The foliation planes are marked by a larger proportion of graphite flflakesakes than the surrounding laminae. TWOTwo thinthin beds of quartzitequarlzite overlie thethe “Volcanic "Volcanic Sub-Group", one'one*justjust above itit at Peg 447 (lll.l0,Sl.l44)(III.lO,Sl.144) and thethe otherothcr at Peg 442 (lil.9.Sl.l43).(111.9.Sl.143). The latterlatter is is an epidote—quartziteepidotequartzite separated from thethe fifirstrst by a small mbuga.mbrrga. The fifirstrst isis a brOwnish»brownish- grey, ratherrather sugary-looking rockrock of distinctly fine-grain containingconlaining a littlelittle microcline and acid plagioclase. Accessory minerals are muscovite (rare),(rare), magnetite, epidote fl(ra'te),are)“ _ \—. and small flakes of biotite having a pleochroism fromfrom a red-brownred-brown toto almost black. The epidote-quartzite,epidotequartzite, a very fifine-grained,ne-grained, sugary-looking white rock, shows a a . streaky laminationlamination due toto thethe segregationsegregation of pale yellow epidote which isis greenish-grmgreenish-grey inin thinthin section and has strong pleochroism. 'MinuteMinute zircons are common scattered throughthrough the the quartz.quartz A typicaltypical line-grainedfine-grained quartzite (lll.l7,(111.17, Sl.57,S1.57, Peg 460) with abundant well- orientated flflakesakes of biotite occurs ata1 thethe eastern end of thethe Tsavo bend toto thethe north of - thethe thrust. thrust. The slide contains minute fragments of almost colourless detrital garnet inin noteworthy quantity, and also minute zircons. ItIt cansearcelycan scarcely be doubted thatthat thisthis ‘ quartzite and othersothen of ratherrather unusual composition occurring on thethe same side of thethe fault fault and a short distancedislanee down theiroadthe raad toto the the west are derived from thethe same source.sotlrce. InIn thesethese (Sls.64.65,66)(Sls.64,65,66) minute zircons areere extremely abundant though thethe - .-garnets present certain differences. These typestypes are now briebrieflyfly described. They includeinclude an extremely well developed group of conspicuously laminatedlaminated (i.(i.e.e. bedded) quartzite:quartzites (III.(111.40Sl.I21,12Ja),*40.3]. 12] .l2]a),‘l associatedassocia\ed with mica-schists,rnicy-Schists, which outcrop about one mile south - _ of Peg 464 on thethe Tsavo traversetraverse (on thethe branch track from Peg 456). One slide shows a mass of slightly kaolinizedkaolinired felspar.felspar, often untwinned and doubtless near toto albite~albite- oligoclase, inin crystals measuring up toto approximately .03.03 in.in. across, interspersed with quartz grains, the smaller ofof Whichwhich are fairlyfairly uniform inin size,size, markedly rounded,iounded, andand - atomabout .005.005 in.in. across,across, the largerlarger grainsgrains being about .01.01 in.in.

: 'Note'Note thethe differencesdilferencu betweenbetween thesethese quartzitesqmrlu'tcs (Sec(See Parkinson,Parkinson, '1921,1921, p.p. 25) andand thosethose conspicuousconspicuous atat Ajow,Ajow; west ofof Bi]Eil Wak.Wak. . . . 15

A little pyrites and a few flflakcsakes of white mica are among the accessory minerals. This moremorc ‘l'elspathicfclspatliic band gives placeplacc tolo the commonercommoncr type of quartzite composed .

of.of, clearlyclcarly dedefinedfined grains of which only a few are l'elspar,fclspar, none apparently being micro- ',

cline. A second slide shows more marked differencesdircrcnces in the size .of the quartzes dedefiningfining ~'

the lamination, the larger among them exhibiting strain shadows. Felspar is represented __._

by a few water-clear crystals, indeindefinitelyfinitely twinned. Flakes of graphite are common. In - the hand specimen a row or two of flflattenedattened quartz pebbles about half an inch long are noteworthy.

A quartzitic rock of unusualunusu.al type may be included herehere. It is a rather slabby iron- Luz-gr

fi

f grey schist (I.(1.165.Sl.135)165.Sl. l35) outcropping about HI+ miles on a bearing of 35° 35" from Bulutoni fi

:‘M'

water hole north of Ngulia I and contains an estimated amount of 25 per cent at: graphite and about half that amount of muscovite in long thin flflakes.akes. A certain amount 1+;

of untwinned, water-clear felspar may occur in this rock as in others but» but the great

:K-mi - majority of the grains appear to be quartz. I A lath-shaped mineral has been so altered into an isotropic brown .substancesubstance as to!o be unidentiunidentifiablefiable by me. The presence of quartzites amongst the -para-gneissespara-gneisses north of the Tsavo is a. not uncommon occurrence and it is suggested as a pOSsiblepossible explanation that the arkoses which apparently form the greater part of the substance of the hills are interbedded with sandstones wherein the felspathic constituent was lacking and which hence were less receptive to the action of the agents of metasomatism.rnetasomatism. '

(b){b) Kyanire-QuartzKynnitc-Quartz Schists The kyanite forms extremely irregular outlines, discontinuous in a thin section. The crystals are embayed or subdivided by quartz grains but are relatively free from inclusions (c.f. Glenday and Parkinson, l926.1926. Pl.PI. 40. Fig.5).Fig. 5). The quartz has a- tendency to be markedly elongated parallel to the foliation but except for cracks and occasional strain shadows does not show marked signs of pressureflnpressure.'In some slidesslidcs (Sl.72)(3.72) sillimanite occurs in minute needles oriented parallel to the foliation, and often,forms often. forms ragged termination fringes on crystals of kyanite.kyanitc. It suggests, in combination with the less spongy character of thethe latterlalter mineral a rather higher degree of metamorphism thanthan isis usually the case with the rocksrocks outcrOppingoutcropping near thethe Mzima bend. Sphene isis an

accessory,acccssory, and minute crystals of magnetite appear toto be characteristiccharacteristic. Rarely, yellow- -‘

- ‘-

brown crystals of rutile are seen. Hematite inin minute brown- brown-redred flflakcsakes isis noticeable ~' inin some slides associated with streaks and clots of magnetite, typicallytypically very closely associated with the skeleton kyanite.

Schists fromfrom Murka Hill are kyanite-quartz associations (Sl.99).*(S1.99).* The characteristic :é'13-?2‘_~11:;;‘.2‘;'-

mineral formsforms longlong blade-like crystals with ragged terminationsterminations but without the host :’ of inclusionsinclusions thatthat distinguishes itit elsewhere. InJn thethe specimen sliced, itit considerably exceeds thethe quartz inin quantity. Small honey-brown crystals of rutile, often idiomorphic,idiomorphic, $55.11:

.,-‘ are an accessory mineral. The hand specimen is a cream-coloured fifibrousbrous rockrock showing «-

an:

thethe quartz as occurring inin shortshort.stringsstrings and lenticleslenticles as well as embedded in the ,. kyanite'kyanite mass. . . (c)(c) KKyotrire-Crapltite-ScliistsyaIIIre-GraplIite-Schief:

4115-3335." The introductionintroduction of wisps and dust of graphite ifii present inin sufsufficientficient quantity

may almost entirely obscure the body ofof.thethe kyanite; so thatthat itit only becomes apparent -

between crossed nicols (lll.(II1.29.Sl.79).29.51 79) For fifieldeld purposes, owing toto thethe incompleteincomplete .‘; crystallization of thethe dominant constituentconstituent, the termteim “incipient""incipient" kyanite isis used. - . .. Such a rockrock (lll.28.Sl.78a)(111.28.Sl.78a) outcropping between thethe Tsavo River and thethe lowlow hill 4‘:

Q. calledc'alled Longa-Longa containsconlains ragged,ragged, extremelyextremcly spongy'spongy porphyroblasts of kyanite, inin a matrix of small fairlyfairly uniform quartz grains, abundant-abundant flflakesakes of graphite and well- marked muscovite. The strong foliation bends round thethe kyanite and the porphyroblastic and the porphyroblastic ‘_."1§-;‘-M-“" order appearsappears toto bebe. kyanite,kyanite, muscovite. graphite, quartz, thoughthough aa fewfew smallsmall grains of thethe thirdthird mineral areare includedincluded inin thethe fifirst.rst.

‘Cf.*Cf. thethe kyanite-quartzkyanite-quwtz schist%his! of thethg TttqaT!tr?kn R,P, area (Parkinson,(Parkipson, 19!}.1913, p. 5.18).538). .

e m"IG ' . .

. A typical schist. (111.32.Sl.67)(111.32.51.67) from Longa-LongaLo'nga-Longa shows rather better formed kyanitc,kyanite, but- but still with plcntifulplentiful inclusions tendinglending to be concentratcdconcentrated in an outcrouter zonc.zone. . Muscovite, abundant specksspecks. of graphite and a constituent believedbelievec! to be altered scapolite, aregre also present. - ’41'.I)Rack:Rocks of doubtfulrlorrhtfrrl origin.origitr, akinnkit~Iolo Hornfels'Hortrfel.~. The origin of these rocks is dimcultdifficult to dctcrmine.determine. They form small, scattered outcrops along half a mile of tncktrack at the Tsavo bend north of the Tsavo Valley thrust. Exposures are far from good. but they are as a whole of hard, quartz-felspar rocks in which some of the important constituent minerals are often not visible to.to- the naked eye. Garnet and epidateepidoteare arc distinctive, and:and pyroxene in irregular flflakes,akes, occasionally altering to pale hornblende, is characteristicchancteristic of some varieties. Minute crystals of zircoh occur in nearlyhearly every slide. The fifirstrst of these rocks (III.25.Sl.65,(lll.25.Sl.65, etc. PqPeg 465), differingdiffering slightly from thethc rest.rcst, is white and speckled witlfwith' hornblende porphyroblasts up -toto one quarter inch long. The crystals constitute almost a quarter of the rock and lie with slight foliation in a very ' ' fifine-grainedne-grained matrix consisting of dusty ill-sorted quartz, enclosed in a felspathic mesh through which are scattered pale pink garnets about .01 in. in diameter. A few small grains of semi-idioblastic epidote, minute crystals of sphene and zircon are the accessory constituents. The felspar (oligoclase) shows zoning and irregular patc‘hy-patchy. twinning. The second (3.64.(Sl.64. PcgPeg 465) is essentially of the same generic type; the garnetsgarn'ets are more irregular in shape and spongy in texture, .04 in. in length or larger, andand- - grains of epidote or zoisite are commoner. The felspar, often untwinned, is an oligoclase. This rock differs from the last in the presence of almost colourlesscolot~rlesspyroxene which has been partly replaced by a very pale hornblende. The third (~ls.66,66a.(Sls.66,66a. Peg 467) is a variation of the same type, and is a gamet- pyroxene-scapolite rock. Irregularlrregular groups of small, rather rounded garnets, with linear . arrangement are associated with small prisms of epidote and a little almost colourless. pyroxene, as before. The very pale green hornblende by which the latter-haslatter.has been.bcen partly replacedrcplaccd shows a faintTaint blue element in its pleochroism. The presence of scapolite and occasional grains of a carbonate arearc, noteworthy differences from the two previous rocks. 'MinuteMinute grains of zircon are again very numerous. About 200 yards to the east, also on the north side of the supposed fault,.afault, .a rather friable though massive iron-grey hornblende-schist (111.24.S|.102.(111.24.Sl.102. PegPcg 463-464) shows some relationship, not macroscopically but microscopically to the preceding rocks. It is fifine-grainedne-grained and the hornblende is just visible to the naked eye. It forms about a quarter of the rock, is apparently originalorigiaal and has normal pleochroism. The accessory constituents are small idioblastic garnefsgarnets averaging about .O1.01 in. in diameter, and' zircons. Many of thelhe felspar grains show _WavyWavy crystallization and zoning; their general composition is that of an oligoclase. In additionbddition there is another mineral mixed haphazard with the garnet, and occurring characteristically in translucent cubes. It lacks the pinkish granulated surface of the garnet and usually measures not more than '.005*.005 in. across. The mineral is isotropic and has a refractive index distinctly higher than garnet. It is left undetermined—inundetermined-in most characters it agrees with,with. perovskite. Certain pyroxene-garnet-gneisses found in the eastern part of the Tsavo traverse, not far from the main-road bridgcbridge are con~parablecomparable with those'justthose 'just described. Of these the firstfirst (1.95.Sl.27,(1.95.8127, Peg 62) was collected thteeaquartersthree‘quarters of a mile south- east of the commencement of the Old Military Road.‘Road: It is a compact grey.grey rock.rock, with slightly greasy lustre showingShowing very slight .foliation,,foliation, of which the constituent minerals.mineral's. are almost indistinguishable to thethf naked eye. In this section the rock is seen to be a pyroxene-garnet-gneiss, the pyroxene occurring in wisps and flakesflakes largely altered

*For‘For the purpose of this traverse, the Old Military Road.Road, a product of the 1914-181914- ltl War,War. commences at a point on the Tsavo a little under three milesinilcs from the Tsavo railway bridge. It was followed (with an unimporlantunimportant diversion tolo the casteast of Signnllcr'sSignaller's Camp)Car'np) until it ended near the junction between the MzirnaMzim3 and Tsavo Rivers. FromFtom its easternustern end a new motor track was Constructedconstructed castwardeastward connecting to the 'main Kenilni-VoiKenani-Voi road. . 1-7 ‘

into green hornblende. ThcThe garnet has no spongy texture and forms fairlyl’airly compact ro~tndcdrounded grains or is partially idiomorphic. Elongated, finger-likefinger-like crystals of quarlzquartz are conspicuous. Microcline is abscntabsent and the fclsparsl'elspars as usl~allyusually is the case are oligoclase to oligoclase-andesine. Magnetite and apatite are accessory minerals. . V

-'. The second slide (SL43)(S1.43) .waswas cut from a rock. outcropping Iflq‘» niilesmiles from thcthe

.:- .commencbment~eommencement of the Old Military Road. Itlt is a pyroxene-garnetpyroxenogarnet gneiss and quartz :' is the dominantdamit~ancconstituc~rt,constituent, and asus in the previousprcvioi~sslide builds extremelyexlrcnrcly elongatedclongatcd crystals, no doubt having consolidated under pressure and slight movement. The 221‘“ fragmentary-looking pyroxene, bluish-green in colour, is partially altered to green 'hornblendehornblende though part is probably'piobably.'original.original. TheIle felspat,felspar, generally only partially - striped, is water-clear and of the same campositioncomposition as-as inin' the last slide. Magnetite,

sphene and apatite .areare accessojaccessory minerals. - ;:.:-:-'x'»::a’sm,z;.

(3) THE Voecmtc SUB-GROUP 5:!“- !.IfI. - [TheseThese rocks, essentially of basic composition and presumed to be of .volcanicVolcanic origin on account of varied composition and finefine banding, are .readilyreadily distinguished in the fieldfield by their clots and streaks .ofof a pale yellow mineral identifiedidentified as epidote. They pass ' by gradations into a foliated acid biotite-gneissbiotite-g-neiss containing pegmatoidalpegmaloidal .veins._veins. They have been found inthree places'places between the Tsavo road bridge and the bend of the river west of the Mzima junction. These occurrences will .bebe discussed in srderorder from eastCast to west. (a)(0) Some nine miles west-south-west of the road bridge at Tsavo there are outcrops of a pyroxene-scapolite-epid~te~gneisspyroxene-scapolite-epidote;gneiss (Sl.l8),($1.18), which is taken as a characteristic type. 'It consists of a matrix of quartz and oligoclase formed round earlier felspar cores. .Epidote occurs as an irregular mesh-work of unoriented, equisized.equisized, grains which-are somelimessometimes enclosed in pale green pyroxene, now altered almost entirely into hornblende. The scapolite forms platy crystalscrystals, having well-marked cleavage and high double refraction. itIt shows early-stagesearly‘stages of alteration. Accessory constituents are a carbonate, rsphene,Esphene, rare apatite and scattered minute crystals of zircon. In a variation (1.108b.~l.l7) of [his rock the pyroxene is seen Lo be completely »

in a variation (I.108b.Sl.l7) of this rock the pyroxene is seen to be completely ”2-" transformed into skeleton plates of dark grass-green hornblende. The amount of < -carbonate,-carbon:ite, which is probably dolomite, is greater than in the previous slide,slide. and the :section shows a wider distribution of conspicuously zoned, but rarely twinned, waIer-water- . -clear.clear secondary felsparlelspar grown around eroded cores and forming a matrix which has ~ .corroded-corroded the other minerals. This zonal felsparfclspar is oligoclase. Epidote is plentiful and :scapolite builds smaller crystals than in the previous rock.rock'. A second variation (l.|08a,Sl.16)(1.108a,S1.16) is more basic. It contains ragged plates of horn- sexy-no.1..." blende;possiblyblende.-possibly secondary; and aaconsiderablea.considerable quantityquantily of equisized grains of unorientated :almost colourless epidote. Scapolite is less"less' common. As before. the untwinncduntwinned nymiw.

r .oligoclase-o|igoc|ase acts locally as a matrix to the other constituents which it has corroded to fl

:some extent. The felspar is dif difficultficult to distinguish in ordinary light from the quartz. -“... Another specimen (1.(1.108,~1;15)'108 Si. 15) almost identical wiihwith the last, is a pale greenish- .white'white rock composed for the mostmod part of minute granules of sugary epidote fleckedflecked -"with -with 'darkdark foliated crystalsCIystals of ,hornblende.hornblende The epidote occurs in thin section as an almost colourless aggregate intergrown with plates of spongy;spongy,' stronglystrohgly, pleochroic 'hornblende,‘hornblende, .08 in. or more in length. The hornblende shows thethe' blue-blue-greeng-reen element :in.'in its pleochroism which distinguishes the same mineral 'iriin the schists of the Suk Hills.Hills, (Glenday and Parkinson, 1927, p. '793)”793) but only rarely .inathosein those of the country under -consideratconsideration. ion. Da&'gyey,Dark grey, fine-grainedfine-grained homblende-hornblende-schistsschists (1.107 and 1.109), are closely associated .with'with those just described. - ... . (&),~h;(b)The second locality is at Signaller'sSignaller‘s CampCamp-onon the left bank of ;hethe Tsavo and :alrnoq..under:almost under Rhodesian Hill.Hiil. In many specimens the rocks are typicaltypical. fine-textured,fine-textured, .non-banded'non-banded homblende-schists,hornblende-schists, occasionally marked by lenticles of felspar and ',quart.z..quartz,., and tinged withwith. yellow owing to the presence of .epidqte:epidote. They areare.in.theic.es$entiaI.in their. esSentiaP #character,-character, the same or closely related to the rocks just described::described; _ ... 1. .2:.. an. , 18

Inin a typical specinicnspecimen (S1.46)lSl.46) original pale grecngreen p).r.oxenepyroxene is common. Even ~rrIn ' the limits of a single section. variation occurs rapidly from:from- a hornblende-schist to a scapolitc-pyroxene-schistscapolite-pyroxene-schist containing accessory carbonate. The scapolite is altcrcdaltered to a fifibrous.brous. brown. opaque mineral referred to pinite. The Telsparfelspar talbite(albite to acid oligoci~se)~oligoclascr is strongly zoried round corroded cores. the exterior portion kavingh'aVing a refractivcrefractive index almost exactly. that of balsam. Sphene and a few grains of ap?tite.apatite. are accessory constituents. Quartz is rare or absent. The principal features of this rock are repeated . in another (S1.47)(Sl.47) from the immediate neighbourhood wherein corrosion by the zoned felspar is conspicuous. Twinning _js.js comlnoncommon in the crystals. the structure running through the corroded core into the outer zone. ThereThere, is a slightly blue tingetingein in thcthe‘ '‘ pleochroism of the hornblende for vibrations parallel to 2.Z. which is rather characteristicCharacteristic ‘ in schists collected in the Suk countryc0untry (Glenday and Parkinson. 1927.1927, p. 793 etcf seq.). Carbonate is far from common.common, but granules of sphene are rather more plentiful than usual. and there are a few grains of apatite. The scapolite shows ihethe fibrousfibrous brown alteralionalteration product in various dcgrees,degrees. certain crystals being in part almost opaque. Inin formation it preceded the hornblende. In this exposure a thin irregular band of quartzite ‘isintercalatedis,intercalated in the basic . schists. It contains some rather dusty albite-oligoclase and distinctive tufts of pale grecngreen actinolite. 5 mm. or less in length. (c) At the third site ("Fortifications").("Fortifications"). rocks (51.63)(SL624) containing scapolite. epidote. cpidote. hornblende and a carbonate in a felspathic (oligoclase) matrix occur as before. They form a well-marked beIt..300belt,,300 to 350 ft. in width overlying ferriferous quartz-schists and overlain in turn by a slabby quartzosequartzOse gneiss (cf. metamorphosed sediments of tHcthe Magadi Railway, Parkinson.Parkinson, 1913.l9l3. p. 538). With them are associated hornblende- epidote-schists. wherein the quartz and felspar form a mosaic, the latter not acting as a matrix to the other constituents as in neighbouring rocks. Minute zircons andand‘a a few grains of apatite are the usual accessory mineralsminelais (SLGI).(51.61). --.."x. --.- As a variation to this series is a fine-grained.fine‘grained. .comprictcompa’ct rock (111.12a.S1.100'.fill.12a.Sl.l00‘. Peg 449)449)-

containing much epidote of a colourless variety. and hornblende and carbonate as , important constituents. TileThe latter is apparently dolomite. The grass-green hornblendehornblende- forms skeleton plates. occasionally a quarter of an inch long which in the specimen mark the foliation by aggregation into thin streaky bands. The epidote, macroscopically withoutwithout, conspicuous arrangement. forms pale yellow clusters. (4) THEScmsrSCHIST SERIES NEARMGANGE. NORTH-WESTOF THE TAITA HILLS . A representative series of rocks from the Mgange Camp area,area. north of the Taita. Hills has been examined. Natural sections are not plentiful and pits had to be dug- usually in very hard ground. The exposures thus made are reached by a track from Maktau which skirts the Taita Hills and connects with Ndi Station on the main railwayrailvvay line. With the efceptioneXCeption of the road east of the Kedai sisal plantation, the track runs near very few outcrops. The schists of Mgange are no doubt of the same'sericssame series as those of the Mzima bend,bend- and one may legitimately infer a continuous basin of deposition for seven or eight miles between the two. The Mgange rocks are,are. however,however. distinguished from those of the Mzima bend by the characteristic commonness of graphite. an absence of crystalline limestones, a diminished quantity of kyanite and the conspicuous appearance of actinolite in fan-like groups or‘or' as well-foliated crystal?crystals half an inch long. In one' consisting almostalmOst entirely of actinolite. a few flakesflakes of graphite are associated.assoeiated. (n)Quarrzites(a) Quartzites are found as thin beds representing metamorphosed silts in the otherwise argillaceous group. They contain hornblende. biotite, garnet and plagioclascplagioclase . as accessory minerals. One such rock (I(lli.89.Sl.|39)lI.89.Sl. 139) may be. taken as a type. It is of a friable nature, light grey in colour. and finelyfinely laminated containing conspicuousconspicuous, graphite flflakes,akes, and spangled with small idioblaslicidioblastic garnelsgarnets which are replaced by.by irregular flakcsflakes of hornblende along certain bands. The graphite is distributed fairly evenly throughout the rock. Graphite dust enclosed in the quartz is irregularly distributed, some grains being crowded with graphite granules, othenothers almost free of them.them..~heThe felspar. felspar which is generally not twinnedtwinned. has a refractive index higher than balsam and is no doubt oligoclase.oligoclase.' . l9-

This rock resembles aa. hornblende-plagioclase-quartzite(111.93.SI.l,l(Ill. 93.SI. I) I) from the sa5‘1esame locality, inIn which hornblcndchornblende isIs distributed evenly as small ragged fl flakesakes throughout the section and shows a faint,faint tinge of blue in its plcochroism.pleochroism. Another quartzite (111.96.Sl.134).(lll.96.SI. I34) originally a_a finefine silt, from Mgange,.showsMgange, shows a littlelifilr. intcrstitialinterstitial microclinemicroclinc wedged between the quartz grains. This is apparently the onlyor)!)' felspar and may,may be a product of metasomatism.*metasomatism.‘ The grains are of fairly uniform size unlike those of quartz which vary considerably and show strain shadows. White fi filmylrny mica, probably developed along slip planes, a red-brownred-brown strongly pleochroic mitamica (length,(length .006 in.) in small rectangular, well-well-foliatedfoliated flakes.flakes, a few crystals of graph9egraphite and a.a considerable nurnber.ofnumber of minute crystals which may be.be zircon, are accessoryaccessaj)' minerals. dB . (b) Graphite-kyanite-scIzis/s.-AGraplu'Ie—kyam'te-sclrisls.—A large variety of schists similar to those of thetbc ' Mzima bend occur, and many are of argillaceous constitution, carrying graphite aii‘da$d kyanite. The graphite,'graphite," apart from dusty inclusions, typically forms.flakesforms flakes having in31‘" average length of about .012 in. and breadth a tenth of that. Their edgesedges. are seen %o{.0 be serrated in thin section. In one rock (111.88a.Sl.126)(Ill.88a.Sl.126) the section consists almas~almost entirely of graphite (say 60 per cent) and quartz slightly clouded with graphite dustdust. Seen with the naked eye it has a uniform dark Ironiron grey colour. Small almost colourleSScolourl&s !:: garnets, with graphitic inclusions are apan accessory constituent. A second example (111.97.Sl.128)(llI.97.Sl.I28) is a massive graphitic-schistgraphitic-sehist with marked foliation ' amounting almost to lamination. It contains kyanite which shows as lath-shaped crystals as much as .2 in. in length set in a pale yellowish matrix consisting oflquart-zof quartz and a partially altered, colourless allotriomorphic mineral forming thin irregular betsbebs or aggregates parallel to the foliation. This second constituent is probably untwinned cordieritecordierite. The kyanite shows relatively few inclusions and has a pale blue tortctr greenish tinge. The rock contains as fairly common constituents flflakesakes of graphite and non-no;- idiomorphicidiornorphic pyrites. Minute idiomorphic crystals of deep redred-brownbrown rutile and minute zircons are rare accessories. In a third specimen (111.84.Sl.121)(Ill..84 Sl. l2-1) a colourlesj'colourless' amphibole is sometimes closet).closeliv associated with the kyanite as a felted mass. Such groups alternating with layers pre-prs- dominantly composed of quartz produces characteristic lamination and a thin slabbi.slabby habit. The rocks are dark grey in colour, the foliation being marked by porphyroblastsporphyrablasts of kyanite up to a quarter of an inch long. As a rule the matrix is unresoli‘zableunresohable by eye or lens—inlens-in the slide the quartz grains barely average 11l/IOO100 in. long. Graphite . flflakesakes are fairly uniformly distributeddistributed. * (c)(c)CanIpact Conzpact Grapl~iticGraplII'II'c RocksRacks wi111with Garnet.--InGarne!.—In these rocks (IlI.79.Sls.l25,125a).(Ill.79.Sls l25.1255). all occurring as far as yet seen near Mgange Camp, foliation is absent in the harirlha$ specimen and the fracture has a dull black almost silky lustre. inIn thin sections, tractrack of foliation can be made out here and there, marked by thin laminae and streagsstrca@ . consisting forfor. the greater part of quartz. Slide 125 consists mainly of very fifinene dusg.du , granules and flflakesakes of graphite with a few conspicuous porphyroblastporphyroblasts of idiomorphicidiornorph~3 red garnet, containing only a few rare specks of graphite. In one instance the garnet is considerably cracked yet retains its form and is nearly a quarter of an inch across. A few crystals almost obliterated by graphitic dust show an elongated outline and such indications of cleavage and double refraction as indicate kyanite, kyanite. while here and there an unmistakable crystal occurs.o'ccurs. Between the graphite specks,specks. irregular pin pointspoiny of quartz, .001 in. across or slightly over, are detectable with crossed nicols. Another specimen (lll.79.Sls.130,132a)(III.79.Sls.130.132a) is essentially similar to the last but rathernthqr fifinerner in grain. It is dull black in colour, sparkles‘withsparkles with minute flakesflakes of graphite and containscontains well-foliated crystals of kyanite. A few rusty. rusty, red spots are probably remnants ‘ofof garnet. The quartz occurs in narrow approximately parallel streaks relatively free from graphite and thus indicates a foliation not otherwise visible. Graphite flflakesakes forming a close mixture with it, seldom exceed .01.O1 in. in length. “GhOsts”"Ghosts" or incipient crystals of kyanite are found as before and may attain a length of .2 in.iq. A much more schistoseschistox rock (IlI.88.Sl.131)(Ill.88.SI. l31) is thinly slabby in habit and conspicuously garnetiferousgametiferous in some laminae. It contains approximately 33 per cent of

' *In’ln ordinary light the felsparIelspar has Ia flintfaint pinkish tinge which allows it to be picked out easitycarily from thelhc quartz. Thus seen it gives theIhc impression of a residual mineral in many cases. . t 20

graphitcgraphite flakes,flakes, which arearc rathcrrather more lumpy in o'utlineGutline than usual.~~sual.The thin elongated crystals of kyanite. not always easy to distinguish from the matrix. are markcdlymarkedly foliated. As before thcthe pale red garnets contain little graphite and are here only partially idioblastic. - .Inin 'anotheranother specimen till.11 11.82.Sls.I82.Sls. l32-32-1l33) 33) a rapid alternation between graphi~icgraphitic and » aluminous laminae.laminae sliawsshows rl~ntthat it is isscntinllyigsscntinlly thethc same as those already described,descrihcd, nanielynamely a compound of quartz and graphitcgraphite containing incipient kyanite crystals full of inclusions. With the exception of a few spaces occupied by predominant quartz, the .graphitegraphite is scattered evenly throughout the rock. The kyanite layers representing a differentdifierent source of material consist of a felted aggregate of that mineral in a quartz matrix containing accessory flakesflakes of graphite. Rare granules of zircon and brown-red rutile are found. Another specimen (111.85.Sls.109,109a)(lll.85.Sls.109,lO9a) is a compactCompact rock, iron-grey in colour and possessing but little schistosity,sc'histosity, which has small brownish-red garnets (about .07 in. in diameter) in a close-grained niatris.matrix. the constituents of which are irresolvahlcirresolvable to. ‘thethe naked eye. The whole sparkles with specks of graphite. It has the appearanccappearance of , being crushed. The exiguous translucent matrix in which the garnets are closclyclosely sctset is composed of quartz and probably felspar and crowded with graphite flflakesakes and . dust. It shows evidence of bending in conformity Withwith the outlines of the garnets. The garnets are practically free from graphite flakes.flakes. althoughaltho~~ghcontaining very numerous minute inclusions of an unidentifiedunidentified' translucent mineral in characteristic blebs. There is also a noticeable quantity of a constituent with prismatic outline, now almost * opaque with greenish- greenish-brownbrown decomposition .products,products, which may be kyaniic.kyanite. The habit and double-refraction as far as can be seen agree with this mineral, which is common in many of the associated rocks. The garnets are greatly cracked- cracked and the cracks.cracks fifilledlled with opaque 'matter.matter. Crystals of mineral considered as kyanite occuroccirr as oriented-oriented feebly translucent inclusions in 'some of them. (If)(4AcII'IIolileActitiolile Sc1ti.rt.r.-OneSclII'.rr.r.-—One specimenspecinien (lll.9l'.$|.|l5l(111.91:S1.11.21 is a heavy dull-grey. well laminated'llminated schist, the constituents of which are us~~allyusually too small to determine by the naked eye. Some layers, rather under half an inch thick. are seen in thin section to be coniposedcomposed practically entirely of tremolite or actinoliteac!inolite associatedasso~iatedwith a Pcwfew flakcsflakes of graphite. The principal mineral mineral, builds long lath-shapedlath-shaped colourlesscolo~~rlesscrystals,crystals,. and has ' a masimummaximum extinction angle of about 20'. ' - Other rocks contain kyanite and tremolite in a:a‘ fclledfelted mass,mass. the two minerals bein'gbeing . not always easy to distinguish from one another. One example (111.80a.Sl.14(lil..80a SI. MD 1) is .macroscopicallymacroscopically greyishgreyish-black,black, heavy, well-laminated,well-laminated. with thin”~hin"stony- ‘stony ‘ layers.layers .AIIotherAnother specimen (lll.90.Sl.l40l(111.90.~1.140) is an iron-grey schist, in which the foliation is marmarkeded by numerous well-formed crystalsciystals of kyanite, up to .2 in. long, with sil19erysilvery lustre on the planes. of cleavage due to the presence of graphite. The greater part of the slideSlide consists of kyanite with graphitepaphite dustdustsegregatedin segregated in strcaksstreaks and zones parallel to !hethe vertical axis and in lines along the partings almost at right angles to it. Crystals have in several cases separated at the partings and the .cracks,cracks or fifissuressSures thus formed have become fifilledlled with graphite and other minerals. Alteration in the direction of the principal cleavage indicates movement after the 'kyanite at least had crystallized. The matrix consists of a fifinene quartz mosaic crowded with graphite specks. Locally it exhibits patchy polarization due to re-crystallization, recalling a ."fruchtschiefer". Now and again .part-part of the outline of such an incipient individual can be distinguished as a definitedefinite boundary and the po1arizatio.npolarization colours areare, then those of kyanite. There is also some evidence of the replacement 'ofof kyanitekyanite'.bybv quartz,quartz. In the felt of kyanite crystals characteristic lozenge-shapedlozenge-shaped cross sections of hornblende cancan' be distinguished. A second slide (IIl.90.S1.151)(lll905l.l51) cut from this specimen shows show; some slightslight. but interesting differences. The same rectangular "ghost"“ghost" crystals are visible here and there in polarized light, and as before areare, much masked by graphite dust. .TheThe larger kyanite crystals contain conspicuous lu.mpslumps and flflakesakes of graphite.graphite, but show a fan-fan-likelike structure, with apparent local replacementreplacement- bxby_..,q quartz uartz between the. kyanite fifilaments.laments . TheseThese. are frequently much bent. A few ..acicuJar,acicular honey-brown hon~y-brown.. .. crystals of,of: rutile .ateaie noteworthy. ' . -. . . :': '7r.. -.-. . -. (w * . . --. :': .:‘ft- - "‘- . 21

(5) THETue CRYSTALL~ECRYSTALLINE LIMESTONES Marbles arcare found, either as isolatcdisolated cxposurcsexposures or in belts consisting of scvcralseveral 'i scparateseparate bcds,beds, at scveralseveral places in thcthe arca.area. They arcare pcrhapsperhaps best developcddeveloped near the .. Voi RivcrRiver whcrewhere it crosses the TavctaTaveta Road near the junction with the MbalcMbale Vaita(Taita .: Hills) Road. The marbles from here have been shown by Miss Hitchins, GovernrncntGovernment .{ Chemist and Assayer, to contain a considerable amount of magnesian carbonate, :i: " .- varying in samples analysed from 38.79 per cent to 42.56 per.per_ cent. The most northerly

., oulcropoutcrop seen in the Taita Hills, north of Msau, contains 5.8 per cent of iron, aluminn,alumina, < ;x _ etc., [hethe highest shownshOWn in any of the analyses made. The section, as is common on the ;;. steep slopes of the Taita Hills,Hills,. is considsrabiyconsiderably slipped,slipped but [hethe marble appeaisappears to be $ . about six feet thick and intercalated between mica-schistsmica--schists strung with acid veins. The ;?, dip is apparently almost due north. 5 ' .. Marbles were also found on the.the- Tsavo River traverse about four miles west of

1.3~a:‘.-'<,-e.='¥.'r':-‘-r'-'1.~“-‘,=E§§au Tsavo where the section, much obscured, appeared to be:-be:— ..

Fine-grained biotite-gneiss. . .-.;-: Marble traversed by a pegmatite vein. Binary gneiss. Marble. ,. Biotite para-gneiss. Marble. ?Quartzite7Quartzite. An ortho-gneiss. The beds are vertical, and [hethe strike conforms with the usual direction, i.e.,I..,: slightly west of north. Small marble beds closely associated with kyanite-schists cross the Longa-Longa track running south from the western part of the main Tsavo traverse. .Magnesian~Magnesian and calcareous carbonates in one sample were found to be 42.83 per cent and 55.88 per _, cent respectively. The.rockThe- rock contained only fractions of 1l per cent of either insoluble material or of oxides other than lime and magnesia. .TheThe marble on the main road south of Kenani Station contains a marked proportion . .ofof graphite which .probablyprobably accounts for the high percentage of insoluble material, viz.viz 7.20 per cent. The magnesian content is slightly lower than the other specimens . analanalysed—33. ysed-33.15 15 per cent. ,

~akenTaken as a whole the marbles are rather coarse, grains averaging about .2 in. .:4 .

. across. w VI-COMPOSITEVl—COMPOSITE GNEISSES OF THE TALTATAITA HILLS .i.

The essential compasitioncomposition of the TairaTaita Hills results from the impregnation of a ,?§fmgtl. great thickness of sedimentary ~ocksrocks of, in general, an argillaceous type by an acidacid, .;fi magma and its volatile constituents, which accomplished a completecomplete'renovation 'renovation of 5'23.¢- the original deposits (cf. Parkinson, 1943 and 1944). ;i9 The intrusive relationship of the invading rocks can be seen in two exposures on

.e-‘teav‘nrz

;; . the Bura Road—~atRoad-at the west end of the Meruga Road and at the hairpin bend of the '

Wusi Road south-west-south-west- of the C.M.S.CM5 station. b a———- lBinghes18 inches : .—--——'I.

Flo.FIG. 4 - IntrusionsImusions ofor biotite-gneissbiotite gneiss and pegmotpegmntitcs, it&. McrugaMeruga Rpnd.Road. near Yale.Yale, Taita HillsHills: : I.I, Biotite-gneissBiotite-gneiss; ; 2, PegmatiticPegmatitie aggregate of quartz and felspar: 3, very dark grey biolitebiotite hornblende gneiss.gneiss, —>

"LII”! .lflltluti' BFeec llIt'lll

“—-

\

FIG. 5 . Section at the west end of the MerugrMeruga Road, Tnita.~oitr'Hills, showingsh&ing the composite naturenaturc of the gneisses:; (u)(rr) biotite augen-gneiss;; (b) acid gneiss, with somelbiotite;; (c) biotite gneiss. becoming - gneisses biotite augen-gneiss acid gneiss. with, some biotite bio~itegnciss. hccoming ' porphyritic at e'.cl. - At these localities the intruding rock is (a) a compact fifine-grainedne-grained gn'eissgneiss speckled with biotite flflakes,akes, and (b) a rather coarse quartz-felspar aggregate with large phenocrysts of felsparfeispar and occasionallyoccasiOnally small nests of mica, occurring as veins or ovoids parallel to or slightly transgressing the general direction of foliation.foliatiorr. Although innumerable variations occur, the essentially consanguineous nature of the intrusions is apparent throughout.throughout..'rheThe road sections show these hard resisting rocks alternating with more extensive exposures of fifinene buff or terra-cotta soil wherein frequentlyfrcqucntlp the bands and foliation of the now decomposed host rock can be plainly discerned. In some instances, fracture of a part of the host rock took place when it was almost in a solid state and was accompanied by the breaking olfoff of fragments,fragmcnts, now _ represented by wisps and filmsfilms of micaceous material, which have been drawn out in the direction of movement and frequently partially absorbed. Such action mayItlay be very local, though variations in the basicity of the mica-schists are doubtless due to s'uchsuch assimilation. Presumably the earliest phase was that of.of..thethe introduction of volatile ' constituents from an underlying magma. The intimate relation existing between the two principal types of acid intrusion militatesmilitate: strongly against the earlier or compact quartz-quartz-lelspar-felspar schist being a felspathic quartzite, for which it might be mistaken. The late .i.J. W. Evans suggested the term . "pegmatoid"“pegmatoid” for such quartz-lelsparquartz-felspar aggregates as are characteristic of these composite gneisses. Partially disintegrated remnants of them can often be seen clearly when other traces of the original structure have entirely disappeared. Excellent examples of this state can bcbe seen in cuttings on the Bura Road where the original rock is reduced practically . to a sand, sufsuffiCientlyficiently compact to stand in a vertical face,face,' but in ,whichwhich‘ "ghosts"ghosts‘ of the all but destroyed micaceous xenoliths are clearly visiblevisible. The writer believes that“thaic'-\ far more of the soil of suchsi~chareas is decayed.schistdecayed schist than would be thought probable at firstfirst sight. . . . Itit is noteworthy (hatthat there is no transition zone from hard to soft rock. The *harder’harder rocks form definitedefinite ridges which extend for miles and form-forrn.thethe highest ground. As an explanation. it is suggested that they occupy positions of original easy permeation by an acid magma or of fluidsfluids derived from it, the introduction of new material in , the form of lit-par-litlit-par-II'! injection producing a reinforced condition capable of resisting stress. On the whole the process was charactdristicallycharactelristically gentle. Uniform grey gneisses and occasionally augen-gneisses are the almost perfectpcrfect hybrids, and show no trace of permeation or intrusion except in the nati~renature of the rock fifinallynally produced. The most characteristic topographical feature of the district are the massive “beds“"beds" of "hard""hard“ rock which form, for instance, the Vuria and Yale ridges, and it is possible that, if a contour map ofo€ the hills were available, the "tectonic" structure of the . whole would become much clearer. A sketch map based on prismatic compass traverses with added form lines has been prepared on a scale of 62,500 and shows this possibility. 23

It shouldsholtld bebc notednolcd that no granitic massn~asshasha; beenbccn seensccn in the tbc area representing the batholith from which the apophyscs ofor acid gneiss and pegmatoids have been derived. An interesting distinction betweenbctwecn this area and the valley ofol the Tsavo is thethc abundanceabundi~nccofor vein and flfloatoat quartz in the latter, Whereas whereas in the formerrormcr both ‘ are rare. VII—SUMMARYVII-SUMM ARY 0FOF GEOLOGICAL CONCLUSIONS I..The The rocks dealt Withwilh in this preliminarypreli~ninary'st~rveysurvey are mainly metamorphosed sedimentssediments. of thethc Basement System.Systeni. ' In Kenya, similar rocks are found in:—in:- (a) the Suk Hills; (17)(b)westwest of Bi]Eil Wait;Wak; (1:)(c) south of .Marsabit;Marsabit; (min(coin the Machakos District and probably elsewhere in the Colony. These various basins of deposition cover collectively an area of approximately 120,000 square miles and one would imagine, failing contrary evidence, that they were lain down in a continuous sheet ofol water, or, that the barriers between adjacent basins were narrow. 2. Throughout this great area the degree of metamorphism was uniform. 3. Volcanic rocks are scantily represented.represcnted. 4. Arenaceous gneisscsgncisscs predominatepredoniinate overovcr much of thethc area. 5. Crystalline limestones, usuallyust~allywith a high magnesium content, occur sporadicalfysporadicalb ' throughout and the argillaceous and calcareous beds tend to be thin and lenticular,Icnticular, indicating quiet deposition in influencedfluenced by currents. 6. It11 is considered probable that the Basement System rocks as seen in Kenya, and their doubtless very extensive southern extensions form a roof pendant, which was partly immersed in a batholith of earlier date thantha? the emplacement of the great Central Batholith of Tanganyika. . 7. It is put forward, but as a suggestion only, that the intrusive orthogneissic dykes exposed near Mtito Andei, along the lower reaches of the Tsavo River, west of thethe railwayrailway bridge, and inin many places Inin thethe Taita Hills, may indicate propinquity toto one wall of the encasingcnasing batholith. 8. The altered sediments ofol thethe Tsavo Basin have beenjdividedbeen.divided intointo two two groups, which have not-not been seen togethertogether inin natural contact. They comprise an earlier group of arenaceous facies,facies, originally probably arkoses, and, a later group largelylargely formed formed of argillaceous sediments. ItIt would appear possible thatthat the the former former has been subjected toto thethe process known as "penetration by soaking".

a Further work may prove an unconformityrlnconlormity between thethe twotwo groups, showing thatthat thethe lowerlower arenaceous sub-sub-divisiondivision formed thethe surface upon which thethe argillaceous .. sediments Werewere lain down. The petrological .characters of thethe twotwo groups which are markedly didifferent,fierent, as well as thethe typestypes of deposition, indicateindicate physical changes which give some support to to this!his suggestion. VIII—ECONOMIC\'III-ECONOMICMINERALS KYANITE KyaniteK.yanite isis chiechieflyfly foundfound on thethe western side of thethe southern part of thethe area. e.g., at Mzima (Longa-Longa)(Longa-Longa) 'andand inin thethe LoosOItoLooso~toand Murka Hills. The mineral occurs inin quantity at thesethese localitieslocalities but isis always fullfull of inclusions.inclusions. Large white crystals with blue centres were not'seen save inin exceptional instances.instances. Microscope examination shows thatthat usually it isis littlelittle more thanthan a skeleton skeleton, thethe principal impurityimpurity being fifinelynely divided iron,iron, or graphite. The outcrops are within about tenten miles of water and transport.transport. ASBESTIFORM TREMOLITE _ Narrow veins of'of thisthis typetype of asbestos have been foundfound inin actinolite-schistactinoiite-schist on .I thethe north sideside of thethe Taita Hills inin thethe Mgange district. It.It isis quite probable.probable thatthat intensiveintensive prospectingprospecting inin thisthis neighbourhood iieighbourhood would resultresult inin more extensiveextensive depositsdeposits beingbeing found. found. - 24 ,

GRAPIIITEGRAPHITE GraphitcGraphite as ;Ia rock constittlcntconstituent is widclywidely sprcadspread in.in thcthe ArgillacconsArgillaceous Group in schistsSchists of various sorts and as specks in qryst;~llinccrystalline limcstoncs.limestoncs. Contamination with flakesflakes of mica is common. If sr~Ciicicntsuflicient tonnage coi~ldcould be foundfound-inin localities favourably situated with respect to transport and watcrthcwater the mincnlmineral wotlldwould probably be worth working. TheThe- -graphitegraphite gneisses extending along the right bank of the Athi are at - present (194])(1941) under exumlnnilanexamination with na vicwview to lltcirtheir ccortorniceconomic exploitation.exploit~tisn. MIC/I PegmatitcsPegmatites are widelywidely. distributed but scldomseldom show mica in sufficientlysufficiently large books to be of value. Rather more favourabltfavourable indications Werewere seen near Mgange in the foothills of the Taita and it is possible that additional prospecting might prove successful.successful IX-REFERENCESIX—REFERENCES d Cilenday.Glenday, V. G. and Parkinson, J.,1., 1926.-"TheI926.—-"The Geology of the Suk Hills." Qlrarr.Quart. Jorrrt~.Journ. Gcol.Geol. Soc. London.London, LXXXII,LXXXll, partpart4. 4, pp. 586-614.586—614. --——- and -—,, 1927.2'~heI927.——"The Kateruk Series and Associated Rocks of the Northern~ohhern Suk Hills (Kenya Colony)."Colony) “ Quart.Qrrorr. Jocrrt~.loam. Geol. Sdc.Soc. London, LXXXIII,LXXXllI. pp. ..790—799.790-799. Grantham,Grantham. D. R;,R.. Temperley, B.B N.N and McConnell,McConnell. R. b.,l3.. 1940.-*'Explanationl940.—-—-"Explana_tion of the Geology oEof Degree,Degree. Sheet No. 17l7 (Kahama)."(Kahama)," Bull. No. [5,IS, Department o€of Lands and Mines,Mines. Geol.Geol Div.,Div. Tanganyjka..Tanganyika. Harker,Harker,A A.,,l939 1939.-Mefan1orpl1ism.—-Metamor—pIIIsm. London. Parkinson,Parkinson." J.,1., 19l9l3.—“On 13.-"On a group of ~etarnor~hosedMetamorphosed. Sediments .situatedsituated between . Machakos and Lake Magadi in British East Africh."Africa " Quart. Jouitl.Jour‘n. Gcol.Geol. Soc..Soc. London, LXlX,LXIX, pp. 534—539.534-539. -—— , l.920.———'Report1920.-"Report on the Geology and Geography of the northern part of the Elas[Easl African Protectorate."Protectorate. Col. Rep. Misc.,Misc" NO.No. 91.9|. Cmd. 729. . -—- ..l943. 1943.-"A——"A note on the Taita Hills, Kenya Colony.*'Colony " Geq.Geog. Jorrrn.lourn. C.I..C...l NO:No. 4, , pp. 161-162.i61-l62. --—— . 1944.-"Discussion1944.-——“Discussion (p. 153) on Yu Chi Cheng'sChengs paper-Thepaper—The Migmatite area around Bettyhill, Sutherland.’Sutherland." Quart. Journ. Geol. Soc. XCIX, parts 3 &Pc 4, pp. 107-148107—148 (paper read 1942).l942) Stoekley,Stockley, G. M., 1943.-"The1943.—"The Pre-Karroo Stratigraphy of Tanganyika'Territory."Tanganyika Territory." Geol. Mag. LXXX. No. 5;5. pp. 161-170.161—170. Tyndale-Tyndale-Biscoe,Biscoe, R.. l940.-—“The1940.-"The Geology of the country around Gwanda." Bull. No. 36,36. Geol.Geol Surv. of S.S Rhodesia. Wade, F. B. and Oates,Qates, F.,F. 1938.-"AnI938.——"An explanation of Degree sheetSheet No.No.52 52 (Dodoma),(Dodoma),"" Short Paper No. 17,l7, Department of Lands and Mines, Geol. Div,DivaiTanganyikaTanganyika.

APPENDIX I ' GRAPHITEDEPOSITS. TSAVO It~trod~rctioti.-DuringIntroductions—During the course of his geological survey of the Mtito Andei- Tsavo area, Dr. Parkinson discovered an extensive belt of graphitegraphitc gneisses west of the confluenceconfluence of the River Tsavo and thethc River Athi, and near Tsavo station on the Kenya~UgandaKenya-Uganda Railway. 'ThoughThough the gneisses are low grade ores several considerationsconsidcra~ions suggested that they were worthy of more detailed examination. PreliminaryPreliminary. work had shown that several graphite bands are present and thatlhat the group extends over at least 15I5 miles. Bands containing sufficientsufficient graphite to be probably workableWorkable appeared to vary from 20 to 50 ft. in thickness, so that sufficientsufficient quantities of ore for large scale-..scale’“--. . operations could be anticipated. Other factors were favourable for mining operations,operations. ' viz..viz., ample perennialperennial. water supplies are available from the River Tsavo, the deposits ' 'arearc close to Tsavo railwayr-dilway station which is only 136 miles by rail from klombasa,Mombasa, and the orcore appcarcdappeared to contain no white mica and little dark mica, thcthe principal.principal "gangue"“"gangue minerals being quartz and felspar. . At one locality a graphite-quartz vein cross-cuttingcrosscutting the gneisses was found. The graphite Inin it is massive and made.made up a considerable partpar1 of the vein, whichwhich' Is,is, how/ever,howcver; of too restricted extentexlent to be of n~orcmore than mineralogical interest. 25

Pro.rpccling.—FurtherPro.rpccrittg.-Further investigationinvestigation of thethe deposits was considered advisable, but ; Dr. Parkinson waswas unfortunately compelled toto relinquishrelinquish his appointment owing toto 4;;: ill-health.ill-health. Field work was, however, carriedcarried on by a prospector, inin thethe north-Westernnorth-western 5 angle of thethc Tsavo-AlhiTsavo-Athi confluence, as thatthat isis thethe most advantageouslyadvantageousIy situated portion of thethe belt.bclt. The graphite-rich horizons werewcre tracedtraced and mapped,mapped, and severalscveral cross-cross- 3. trencheslrenches wtrewkre dug toto a a depth of tenten feetfeet forlor samplingsampling and and to to determine thethe width of thethc bands.bands.

'0 moo Imoo 310004000 15900,"; MA.

1.T FormForm lineslines 1394' ""'\ SpotSpoL height:heighbs byby aneroidaneroid \\\ 'GraphiceGraphite bear-inbearing ' '. \\\ Formations-ForrnaLions - A.B.C.D-E.EG,&A.8.C.D-E.f.6.L H.H. .. 411'Am CrossCross branchestrenches :3rl Paragneisse‘s,P8raqneisses. -.

' 5.“’V9Y€dS.~veyedbyby 6.A.Branh5£rom8-~.6rannstrorn . . ' FIG.FIG.6 6 _ ‘ GraphiteGraphil~deposits,deposits, Tsavo.Tsavo. 26

This investigation revealedrevealcd the prcsenccpresence of eight graphite-rich bands, bands. indicatedindicatcd by letterslettcrs A to H on Fig. l.1. The strikestrikc of the bands was found round to be generallygcnerally about 335' and the dip steepstcep to vertical.vcrticql. SomeSomc bands were wcre traced continuously over an distancedistancc of tWotwo miles. Over much of the strikcstrike the overburden was one foot or less in depth, and in many placesplaccs the gneissesgncisscs werewcrc exposedexposcd at surface.surfacc. At otherothcr places they werewcre decomposed to depthsdcpths of up to six feetfcet and yielded friable ore. At greatergreatcr depths blasting wasWas necessary to pcnctratepenetrate the rock. though it was obvious that it would be readily amenable to crushing. By aneroid it was determined that the highest parts of the bands.varied bands .varied from .20 to ZQO240 feetfcet above the river beds. . SanrplittgSampling andund AssayAS.YCI>*reslr1t.r.-lnresults—In all 15 trenchestrefiches were excavated,cxcavated, and samples, taken in horizontal cuts over lengths ofoE 10 feet, were obtained from 10 of them. The samples were crushed and the graphite flfloatedoated off and the approximate percentage of carbon in the concentrate determined. The results were as follows:follows:-— "l:/, orOF EmAcrumaESTRA~ABLEGRAPHITE. -..-- - EastEast. End of Trench. , West\VPS$ End of Trench.Tmncll.

. ' . Average TRENCH. 0-10 11-. 10-2010—20 ft.ft.. 20-30 ft. 20-4020-10 ft.ft.. 40—60&O ft. for Trench.

AI . . 6.26 3.83 2.85 3.70 3.47 . 4.0 A.III 5.50 4.87 1.87 . 5.146.14 —- 4.3 8-8- A.IV . . 6.97 9.03 7.77-1.1 I —- —- 7.9‘ BI . . . . 5.83 . —- —- —- —-- 5.8 0.1 . . 6.24 t 7.68 — — —- 6.0 CJT . . . . 4.75 I 4.19 — — —- 4.4 DJ . . . . 6.93 ; 5.70 ——- l —- 6.3 ‘ DJI . . 5.66 l 9.47 6.72fi.72 I a5.1616 (0.64) 6.7 D.III 8.12 I 8.018.94 1I 55.84S4 j 0.6464 —- 7.4 13.11 . . 6.62 ' 4.67 I —- ..I- ——- — 13.6 Weighted ow-rnl] Iwnmgn vnluo ...... =1 5.8 per cent. TheThese resultsresulls were obtained by fl flotationotation of —30-30 meshniesh materialmateriaj in a smallsniall laboratory cell using pine oil 3sas frothcr,frother, the concentrate beingbeing' washed. dried.dried, ignited at a low temperature (about 400°C.)400T.) and finallyfinally ignited at 900‘C.9W°C. to burn off the carbon. No great accuracy can be clainiedclaimed Torfor the results, butb~ttthey were sufsufticient.forficient‘for the purpose. Perrograp1ry.-ExaminationsPerrngraplry.—Examinations of thin sections by Dr. C. S. Hitchen disclosed that the principal constituents of the ore are quartz. felspar and graphite, the latter in . characteristic flflakes.akes. attaining in some cases a diameter of fifiveve mm. Subordinate biotite. some of which is bleached, was noted and minute amounts of sericite. The felspar was found to be of potash and soda lime varieties,*varieties,‘ mainly fresh but in part affected by kaolinization that has spread along cracks and cleavages. Zircon is present as an - accessory. , ExpcrinrerrtsExperiments otton tlrcthe e.rtroctiorrextraction of the graphitegrap1rite.-Experiments.-—Experiments were carried out by Hitchen to determine the amenability of the ore to fl flotation.otation. It was found that a good scparationseparation could be affected using pincpine oil (up to 1 lb.Ib. per ton, a fifiguregure that was - .'considered considered to be considerably in excess of what would be required in mill practice) as a frother,irother, and 1-3 Ib.lb. per ton of sodium silicate as a depressant. With ore crushedcrushcd to -40—40 mesh an initial separation of 98 per cent was obtained, using pulp densities ofol 7-107—10 per cent solids. Using -30~30 mesh ore the separation appeared to be about 90 per - cent. Further tests shOWed showed that if the froth was allowed to stand for a period of a half to one hour a considerable amount of gangue fell away from it,ii, suggesting that the use of shallow settling tanks between rougher and cleaner cells would be advantageous. - _. Inin addition it was found that on cn~shingcmshing the ore to about —10-mesh- 10-mesh the greater&eater part of the graphite and felspar was reduced to a fifinergrade,ner’grade, the coarser fraction consisting of quartz grains containing little graphite. From this it was judged that partial reduction followed .by screening prior to flflotationotation would materially reduce the cost of extraction.

' *Dr.‘Dr. Parkinson found only oligoctaseoligoclrse in his slides, Ihoughthough in one caseasc it‘wasiiwas slightly perthitic. 26

This investigationinvcstiption revealedrevealcd the presence of eight graphite-rich bands, indicated by letters A to H on Fig. l.1. The strikestrikc of the bands was found to be generally about 335°335' and the dip steepstcep to vertical.vcrtic?l. Some bands were wcre traced continuously over a distance of two miles. Over much of the strikcstrike the overburdenovcrburdcn was one foot or less in depth, and in many placesplaccs the gneissesgncisscs werewcre exposed at surface.sitrfacc. At other places they were wcre decomposed to depths of up to six feet fcet and yielded friable ore. At greater depths blasting was necessary to penetratepcnctnte the rock. though it was obvious that it would be readily amenable to crushing. By aneroid it was determined that the highest parts of the bands.van'edbands.varied from .20 to ZQO240 feetfcet above the river beds. . ' SamplingSorrrplittg undand As.mpAssay results—1nreslr1l.r.-In all 15IS trenches were excavated, and samples, taken in horizontal eutscuts over lengths of 10 feet, were obtained from'from- 10 of them. The samples were crushed and the graphite fl floatedoated off and the approximate percentage ofsf carbon in the concentrate determined. The results were as follows:follows:-— IV or EXTRAOTABLE GRAPHITE.

EaatEast End of Trcncli.Trench. , West-\V~,st. End of Trench.Tmticli,

‘ ' . AverageAvcrnpc TRENCH. 0—10 h. 10—20 ft. 20-3020—30 ft. 20-40 ft. 40—60 ft. for Trench.Trcncl~.

AI . . 6.26 3.83 2.85 3.70 3.47 4.0 A.III 5.50 4.87 1.87 5.14 — 4.3 11.1" 6.97 9.03 7-1.1 77.-- 1 — — 7.9‘7.9 BI . 5.83 — —- — — 5.8 0.1 . . 6.24 7.68 — I — — 6.0 CJT . . . . 4.75 4.19 —-- I — — 4.4 - I 6.3 D.I .. .. 6.9.1 , 6.70 — i — -— 6.3 -- DJI . . . 5.65 i 9.47 17.726-72 0.16 (0.64) 6.7 13.111 8.12 I 8.94 5.345.81 j 0.64 — 7.45.4 13.11 .. 6.62 5 4.67 _- ''1 — — 6.6 WI-iglitcrlWeighted a\-rmlloverall nvom~onvnrngn vnliirvnhir- ...... =-= 5.8 per cent.eont. TlicseThese resullsresults were obtained by flotationflotation of —30-30 meshnicsh materialrnateriaj in a small laboratory cell using pine oil as frothcr,frother the concentrate beingbeing' washed. dried, ignitedigniled at a low te~nperaturetemperature (about 400°C.)and finallyfinally ignitedignitecl at 900'C.90°C.to burn off the carbon. No great accuracy can be claimcdclaimed for the results, but they were sulsuficient.forficient'for the purpose. Pelrograp1ry.-ExaminationsPelmgraphy.—Examinations of thin sections by Dr. C. S. Hitchen disclosed that the principal constituents of the are ore are quartz. felspar and graphite, the latterlatler in characteristic flakes.flakes. attaining in some cases a diameter of fifiveve mm. Subordinate biotite.bioiite. some of which is bleached, was noted and minute amounts of sericite. The felspar was found to be of potash and soda lime varieties,'varieties.‘ mainly fresh but in part affected by kaolinization that has spread along cracks and cleavages. Zircon is present as an accessory. . . ExperinrerrlsEcrI'nIenIs on [liethe e.rlraclionextraction of rlrethe graphite.grop1rite.-Experimen—Experiments were carried out by Hitchen to determine the amenability of the ore to fl flotation.otation. It was found that a good separation could be affected using pine oil (up to 1 lb.Ib. per ton, a fifiguregure that was - ‘considered,considered to be considerably in excess of what would be required in mill practice) as a frother, and 1-3 lb.Ib. per ton of sodium silicate as a depressant. With ore crushed to -40—40 mesh an initial separation of 98 per cent was obtained, using pulp densities of 7-107—10 per cent solids. Using -30-—30 mesh ore the separation appeared to be about 90 per - cent. Further tests showed that if the froth was allowed to stand for a period of a half to one hour a considerable amount of gangue fell away from it, suggesting that the use of shallow settling tanks between rougher and cleaner cells would be advantageous. - ._ Inin addition it was found that on crushing the ore to about —10-mesh- 10-mesh the greaterireater part of the graphite and felspar was reduced to a fi finer'grade,nei‘grade, the coarser fraction consisting of quartz grains containing little graphite. From this it was judged that partial reduction followed .by screening prior to flBolationotation would materially reduce the cost of extraction. - *Dr.‘Dr. Parkinson roundfound only oligoclascoligoclase in his slides, though in one caseuse it‘iiwas slightly perthitic. 27

A sample of concentrates containing 84.884.8 per cent carbon produced by thethe method described was scntsent together with samples of the ore to the JmpcrialImperial Institute.institute. ThcscThese Were submitted to a refractories company who reported that the deposits were worthy wcrc submitted to a refractories company who rcported that the deposits werc worthy , of exploitation and suggested that, if available, friable surface oreare should be workedWorked and treated in launders as has bccnbeen the practice on some MadegnscarMadagascar minesmines. Itit was ; latcrlater staledstated that thcthe Tsavo rnatcrinlmaterial was the most promising Colo~lialColonial grnphitcgraphite that had i becnbeen examined. CommercialConuttercia1 r.rpluilution.-Asexplanations—As the deposits appeared worthy of serious considera- tion applications were invited from the publicubtic in May, 1942, to work a concession in I: ,! . the north-west angle betweenbeIWeen the River Athi and the River Tsavo. In January, 1943,I943, '::; a special liccncelicence was issuedissired to Messrs. Kitmag, Ltd., covering an area of 160 square miles, and including all tllcthe known deposits. Preliminary sampling had indicated that over the area tested oreare averaging about seven per cent graphite could be expected. As a result of &erimentsexperiments it was decided that-thethat 'the following method of extraction '’ should be adoptedadapted provisionally:—provisionally: - 1.l. Crush to 14 mesh. 2. Soak 12 hours in water. 3. Flotation (in hatchbatch tests the proportions found most satisfactory were: ore,ore. ~ 4+ 1b.,Ib., water, 2+2% gal..gal., pinepihe oil, 10 drops). 4. Dry concentrate. . 5. Screen dried concentrate on 20, a,40. 60(10 and if'necusaryif'necessary on 90 mesh sieves. 6. Roll each grade, to flattenflatten graphite and comminute quartz and felspar. . 7. Re-screen each grade, when most of the gangue is passed, graphite being retained and yielding concentrates of 85 per cent or more'more‘ carbon content.

The undersizes from the. -60 mesh or -90—90 screenings were to be retained for further ,' Ireatment.treatment. The screen analyses of products obtained bymihisby'this process was:-was:— Per cent ++20 20 meshmestM T.M.M.M. 15.7l5.7 —201.M-20 I.M.M.+40M. +40 mesh BUSB.S. 37.4 ~40-40 B.S.8.8. ++60 60 mesh BUSB.S. 46.9 .. (Complete sets of screehsscree‘ns of one system wereWere not available). When work was begun on the concession a pilot plant capable of dealingdcaling with one

'!-.,.

ton of oreare per day was erected. SubsequentlySubsequently a further sdecialspecial licence was granted !L

to Messrs. Kitmag, Ltd.,Ltd. forlor a period of two years over. an area of 44 square miles, k:4.- -. i? covering the deposits north of the River Tsavo. li Plant was erected including a two head stamp battery, flotatib~flotation cells, rolls, vibrating ,$," ;:.e-.-.'-:P4.:z' . screens and driers. Provision was also made for obtaining an air-floatedair~floated fraction during screening. The stamps proved urisatisfactoryunsatisfactory and it waswasréalized .realized that rolls would give a moremere satisfactory.comminutionsatisfactory comminution of the ore. Full scale rolls were not obtained, however, and the mine continued to operate as best it could with the inacientinefi‘icient plant already installed. . . . The grades of graphite obtained, in relatively small quantities, are indicated by -1 the following test results:-results. ——

Grade of Concentrate. Treatment. % C. % Moisture. . Remarks. ' -. - .1..i._ , +20 mesh 88.1 —— — ' .. -20+40—20+40 ,;,, ... Once 85.1 — ’—-. ..~ 40+60.,,-—40+60 . ,, .. tolled _ 75.3 —— -—— 2. '..‘. . +20 ,,., .. I 92.6 -— --- -20+40-—-20+40 ,...... Twice 01.091.0 -— --— 40+60 rolled 83.0 .——40+co ,.,, ... . . rolled 83.9 ,—- -.— I 3. '--20+40~20+40 ,.,, .. 9L101.1 . 0.24 ‘ . 40+00~40+00 ,,,. . . Thrice 88.8 i::0.24 ._ ibricantLubricant' : , . . -60+80—-60+80 ,, .. _ rolled 95.3 ' 0.32 > typc.type. C ' , . . 4.4- +20 ,. ... . ltoicorolJedTwieo rolled 94.3 0.810.61 Crucible grade.gmde. . . i . ,.:,

;:I :1' 28'

The size gradinggreding of some of the concentrates (crucible grade)gi-ade) is shown by the resultsr&ults of three tests detailed below:below:-— -

8611mm8m~mGit/mum.Gnhbmn. - Wmon-r %. \'.. - - *- 1 TestTest 1I. Tm. 2. Tests.Tpnl. 3.

+204-20 meshmmh I.M,M. 4.4 5.7 4.4 -.—20.-20 I.M.M.1.W.M. +30 ,,.. B.S...B.S.. . “J 21.6, 19.8 —20-20B.S.13.3. +40+NI ,,.. B.S...B.S. .. . . 30.2 34.6 —4013.s.40B.S. +60- ,,. B.S...B.S...... 35.0 35.4 33.7 —60-GO 15.8.B.S. +90+go ,,.. .na.RS...... 15.7 51.8 5.0 - —9n-90 as.n.s. ,.,* ...... 3.3_3.3 2.2 _2.2 99.509.6 99.9 99.7 - CarbonClubon Content ... . . 90.4% 1 ' 84.7% 1 34.6%84.6%

ItJl is reportedrcport;d that thethe mine has been closed for production since April,.l945.~~ri1,'1945. Interest in Europe is, however, still maintained inin the deposits, and in the latterlatter part of 1945 a bulk sample of the oreore. presumably for extraction tests, was sent to England.

Production—TheProduction.-The production from the mine according to returns inin the fifilesles of the Mining and Geological Department Isis as follows:follows :'-—

Ore CrucibleyeFoundry/";;" Lubricant Stove BhlishinWlish. in Mom. Treated Grade in .I"" Grade in Grade in Ntunber ol‘or Tons. lb. lb. . lb.Ib. Blacks.Blo&s. - 1944. . JuneJurx . . . . No recordrecord 336 — .g — —- July-July . . .. ,, ,, 145 56s — — AugustAUFW . . - ,; ,, 3,360 8,960 — —-‘ September . . ,, ' ,, — 8,960 2,390 —- October .. -, 220 ' -— —- 2,630‘ ~— November . . 390 —- 11,300" — 576‘ December . . 432 6,319' -— — ——

19451946 ' January .. . . none — 1 1,200 _— 800’ FebruaryFebn~ary . . . . 2302 30 20,160 (lb; concentrates) — MuchMarch.:. .' . . . . none 3,920 1,120 1,120 - 2,690 (1,730‘) May ‘' '...... none . —- — 1.120 -

" Denotes ealee., The value of these.these products isis not known but isis probably. of thethe order of £1,500.f 1,500.

Constitution of thetl~eashas18 residue—Theresidue.-The ashes obtained by calcinationcalcinatibn of samples submitted forfor carbon determination were examined under the.the. microscope. Minerals identiidentifiedfied were generally small grains of redred ironiron ore, quartzand quartz .and felspar,felspar, occasional grains of cf. ilmenite,ilmenite, white mica, cf. clinozoisite and rutile, scattered largelarge fl5aksakes of biotite and abundant plates of aa, colourless feebly birefringent mineral thatthat was thought toto be probably a dehydrated kaolinite. The latterlatter frequently occurs as skeletonskeletop plates, and evidentlye\$dently itit isis inin the the rock intimatelyintimately intermeshedintermeshed with thethe graphite flflakes,akes, so thatthat itsiis elimination by ordinaryordinary processesprocesses of ore-dressiingore-dreslng isis impracticable.impracticable. -- Partial analysisanalysis of aa samplesample of ashash gavegave thethe followingfoJlowing result:'—result:- 29

At1oiY.r;sAnalysis of ad:ad^ frontfrom -20-'20 arrdand --20+ 20+ 40 nreslrmesh samplessorrlples in equal amou~lh.amounts. (Ash 10to per cent) Per cent ' SiO,SiO3 ...... 64.29 ...... _ .. .. 21.13 AIzO,Al,0a ...... •...... 21.13 Fe,O,I-‘e,0a ...... 5-145.14 MgO ...... 1.86 CaO ...... 2.78 Na,ONa=0 II.. .II. .II. I:.. .CI' . 22. . .II. .I.’. 0.58ofss _ < K,OK_,0 ...... ‘ ...... 3.16 - ' ,.

T10,TiO, .... f ...... 0.84 2' he»? - 4: Total ...... -99.78 Analyst, Miss A. F. R. Hitehins,Hitchins, ClrenristChemist and Assayer. Apparently no petrographic examination was madcmade of the sampltssamplbs before analysis, and it is difficultdifl'icult to derive from it any reliable idea ofof’ the proportions of the minerals present. Assuming, however, that it had the constitution of ashes previously examined, it appears probable that the platy colourless mineral forming the greater part of the residues, is more akin to pyrophyllite than kaolinite or at least to a more highly silicated member of the hydrous aluminium silicate family. The optical properties of the dehydrated mineral in no way suggest pyrophyllite, though correspondence wouldwould? not be expected after the mineral has been subjected to calcination, at a tempemuretemperature sufficientlysufliciently high to allow the elimination of the total carbon content. APPENDIX 11 KyANrn-zKYANITEDEPOSITS. MURKA Infrod~~cfior~.-ItIntroduclion.——It will be apparent from Dr. Parkinson’sParkinson's report that he discovered pumerousnumerous occurrences of kyanite-bearing rocks among'his Argillaceous group ofof“ the Basement System. Itit is clear from the description he gives that he realized that.thattlie tlre deposits most likely to be of economic value were those on Murka Hill in the south-sauth- westernWestern part of the area. InJn 1942, Messrs. Markham and Co., beeamebecame interested'interate& in the production of kyanitekya‘nite refractories and _Sir.Sir Charles Markham who was prospecting thcthe area concluded that the deposits on Murka are extensive, including considerableconsiderablc

~ tonnagcs of readily worked boulders at the base of the hill, and worthy of exploitation. '

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As a result mining claims covering the deposits wereWere ‘pegged'pegged in October.October, 1942. SinceSincc fi then.then the deposits havehaVe been worked discontinuously according to demand, and research has been carried out in connection with calcination to convert the kyanite to mullite for ‘ use in refractories. Messrs. Markham and Co. announced the production of mullite vireyfb-L’VL' refractories in January, 1943,l943 and at a latcrlater period they have been made by the JfidustrialIndustrial Management Board. Geology of rltethe Deposits—Dr.Deposits.-Dr. B. N. Temperley of the Geological Survey of Tanganyika visited Murka in October.October, 1942,I942, while acting as geologist for the East African IndustrialTndustrial Research and Development,Devclopn~cnt.Jioard.Board. HcHe was able to spend only :ta few hours at the I-litylocality but determincddetermiacd that the kyanitekyanile deposits occur as interbeds in a series of siliceoussiliceor~sgncisses, wilhwith :I:1 clipdip dof abor~tabout 30" to the north-east, i.e., thcthe western face of thethc hill is a scarp slope. and the eastern facelace adip-slope.a. dip-slope. He found that one ofqf the kyanite-rich beds forms the crest of !hethe hill which extends, at an altitude ' ‘ of about 300 feet above the surroundingsurcor~ndingplain, over about l,0001,000 yards, and as a low ' ridge that continues loto the north of the hill. Huge segregations of almost pure kyanite ranging up to several hundreds of 'tonstons in weight were noted, particularly at the southern end of the hill, where they werewcre considered to have fallen from the outcrOpsoutcrops on the ridge. Temperley considered that the segregations have survived disintegratiopdisintegration owing to their lack of foliation and freedomfrcedoni from easily disintegrated minerals. He concl\ldedconcluded that reserves are extensive. .. In June, 1943, the deposits werewerc re-examined by Dr. E-E. Parsons.Prirsdns. He confirmedconfirmed generally 'thethe findingsfindings of previousPrevious investigators, and noted that the kyanite segregation:segregaGons vary from a few inchainches loto six or seven feet in diameter, andaod have “skins”"skins" of kyanite 30

k11c;ssgnciss containing quartzQuartz and rutile. The kyanite of the segregations is ofor bluish type.type, and bctwccnbetween contiguous masses then:there are felts of white kyanite that were shown micro- scopically to be remarkably pure. Dr. Parsons found that segregations of workable size wcrewere rare at points more than 250 yards north of the southern end of the hill. On its ' south side liehe discovered two extensive pockets and was able to trace at least threcthree .'indistinct indistinct bands on the west ~PCC.face. the bands thinning and fingeringfingering out to the north. He mapped three zones of massive dctritaldetrital kyanite on the low ground south of thcthe hill and considered that they represent the remains of more readily weathered kyanite gneiss bands rather than‘materialthan,material fallen from the massivcmassive kyanite zones on the present hill. . Kyanite deposits that appear toto: be closelyc105ely similar to those of Murka have also been described from Nyasaland (B11ll.(Bull. Itrtp.Imp. It~sf.Inst. XXXVI, No. 4, 1938;~.l938,-p. 495). Cor~r/i(utionCorminm‘au ,andand contpositioncomposition of tlrethe om.-Separationore—Separation in heavy liquids olof ground samples of the ore yield heavyhe'avy fractions consisting mainly of kyanite with a few rutile grains, and light fractions consisting mainly of quartz but sometimes with a little mica . and felspar. Separations made at various times gave the following results:-results:— 121 2 3 4 5.5 Moisture ...... _ . .. 0.25 -—— ' -—'- ' -— -—— Light fraction ...... 2.8 . S8 16.8 0.6 0.88 KyanitcKyanite and a ' . - littlclittle rutilc ...... -----96.9590.95 p 9292_ 82.8 99.4 99.12 TolaTotals Is ‘ ...... 100.00 100 1 99.6 100.0 100.00 -- --- I. A hand-pickcdhand-picked sample,sample. broniorornibromoform separation. 2. AvcrageAverage hand sample.sample, bmmoformbromoform separation. ~3.3. Run-of-mine ore, bcrorcbefore hand-picking, bromorormbromoform scparation.separation. ‘ 4. BroniolorrnBromoform sepiaratio11separation of a sample from.from.a a shipping consignment: dried and crushed to -—60 60 mesh. 5. Separation by washing'washing Inin water of i~notheranother portion of the same sample, as No. 4, dried and crushed to —60- 60 mesh. It was roundfound that with a Iitllclittle hand-picking.hand-picking. orcore orof YO-9590—95 per ccnicent. purity coitldcould be consistently obtained. Two chemical analyses of thc malerial are available (analyses of otllcrother kyanites arcare quoted for comparison):—comparison) :- I 2 A B ' C SiO,SiO: ...... 37.38 35.88 36.8 34.66 31.07 _ A1,0,A1._,0J ...... 59.65 61.00 63.2 60.8160.84 65.52 FezO,Fe=OJ ...... 0.56 0.30 -—- ' 0.07 1.50 MgO ...... 0.07 0.0s0.08 -— 'n.d. 0.04 CaO ...... 0.27 0.12 -— n.d. 0.34 '‘ Na,ONa=0 ...... n.d. 0.24 ,-,— n.d. '‘ n.d. ' K,OK,o :. . . . . n.d. 0.12 -- 11.d.n.d. n.d. Loss on ignition ..... - 0.60 .0600.60 ---— 0.90 -— TiO,TIO, ...... _ 1.09 1.48 -— I.1.18 1.431.43 . - - - - - Totals ... . 99.62 99.82 100.0 97.65 99.90 - - - - - I. Representative sample taken from a 300 t0nton consignment. Analyst,Analyst Miss A. F. R. Hitchens, Government Chemist and Assayer. 2. Hand sample, analysed inIn London.Landon. Firing tests on this material at 1,300°C.,1,30OoC., gave . . satisfactory results. )4.A. Pure kyanite. . 8.0. Indian kyanite. Quoted from Jorrrr~.Journ. AtrreiAmer. CerorrricCeramic Soc. 19, No. 1, ,.l9261926. . . C.~..AverigeAverage analysis of calcined indian~ndiankyanite. Quoted fromfrom B~dl.Brill. Itnp.Imp. Ins/.Inns! . ..XXXVl,XXXVI, No. 4, 1938, p. 497. 31

ThcscThese rcsultsresults indicate approxiniatclyapproximately 94 and 96 pcrper cent. p~~ritypurity in the twoIWO i(cnyaKenya saniplcssamples rcspcctivcly.respectively. It is noteworthy that thc bulkbi~lkof thethc inipi~rityimpurity is TiO, (as rutilc), that has no adverse cffecteffect inIn use, so that tlicthc kyanite can be considered as virtually one or more per cent purer than the figuresfigures quolcd.quoted. Cottver~ionConversion ro(0 tr~rtllitc.-ExtensiveIIIIIlII'le.—Exlensive experiments on the conversion of kyanitckyanite to mullite havchave becnbeen carried out.out' by the East African Industrialindustrial Research and Management Boards, and by the end of 1944 consistently high ritesrates of conversion were being obtained . in the commercial kilns of the latter Board. It was also found pOSsiblepossible to produce a grog with mechanical strength comparable. with that of commercial samples of mullite. High grade refractories are being manufactured by the Management Board from this mullite. Prodrrcriot~.-TheProduction—The production between January, 1943, and January,January,. 1945, according to records in the filesfiles of the Mining and Geological Department was a littlelittlc over 936 tons. The value of this in KcnyaKenya rnuslmust be of the order of £3,500.f3,500. APPENDIX 111III . MAGNESITEMAGNESlTE DEPOSITS, KINYIKI . In~rodrrc~io~r.-TheIIIIrorIIIcII'on.—The gcologygeology of Kinyiki Hill which lies a few miles north of Mtitohitito Andci station is not dealtdeal1 with by Dr. Parkinson in his report. So far as is known thcthe occurrenccoccurrence of valuable minerals there was fit-stfirst appreciated by a prospector who, in 1936, pegged mining claims coveringcovcring the hill on behalf of the KcnyaKenya Asbestos Co. The claims were kept extant by various peoplcpeople under the same company namoname until’ until May 1940, when theythcy were transferred to Kenya MagnesigMagnesitc Ltd., who are the present holders. . . A sample of n~agnesitemagnesite from lhcthe claims was examined and analysed by thcthe Imperialimperial Institute in 1939 and was pronounced loto bebcmof_of .high quality (Imp.(Itnp. IIIII.Ituf. Ann.AIIJI; Rep. for 1940, p. 37). . . . GculogyGeology nJof KitryikiKI'IIyI'kI' Ifill.-The[ML—The hill and its surroundings Werewere examinedexanlined inIn 1936 and again in 1940 by C. S. Hitchen who reported that it stands about 250 feet above bhcthe surrounding plain and consists of a pipc-likepipe-like intrusion of dunite piercing hornblende schists. He foundfoi~ndthe dunite to be freqllcntlyfrequently carbonated at surfacc,surface, but when freshfre..h unusuallyun~~suallyfreefrec from scrpentinizationscrpentinizalion and spinel segregations. The intrllsionintrusion is the host of extensive rafts'ral‘ts of hornblende schist, grading into hornblende granulites and amphibolites. it is cut by pegmatites in the eastern part of the hill (Fig. 7). Maplesire.-DepositsMagIIesire.—Deposits of amorphous magnesite are present-present almost everywhere on the hill, and occur as anastomosing veins and veinlets running in all directions through the dunite. The veins vary in size from stringers to bodies 12 to 18 in. inin' thickness. One seen on the hill top .hadhad a thickness of about a foot and could be traced over a distance of 75 ft. On the west side of the hill several veins are 6 to 8 in. in width and persist laterally for 20 to 30 ft. - During his second visit Hitchen had the he opportunity loto measure sections in adits and opencasls,opencasts, and found that the magnesite-richmagnesitc-rich dunite appears to occur in layers or zones 10 to 15 ft. in thickness. The average of 42 measurementsn~easurementsmade at intervals in one aditedit showed that approximately 2616 per cent of the wall-rocks consistedcousisted of magnesite. This was presumably on a magnesite-rich zone and cannot'be'cannot be taken as representative of the hill as a wholc.whole. It appears that magnesite veinlets arearc less frequent on the northern -. part of the hill. In trenches on the south~westsouth-west of the hill, dunite was exposed containing about 10 per cent of magnesite, bulbut mostly in veinletsveiplets from a half to three inches wide. During working thehe total magnesiternagnesite content was found in places to "diminish'diminish to six per cent with low silica ore constituting about one half. y . During his earlier visit Hitchen noted that asbestos veins which are also emplaced in the dunite were capped by magnesite, and that'that inIn some of the thinner magnesiteaagnesite veins a relictrelic! eross-cross-fibre-fibre structure could be seen. He sUgge#edsuggested that thethe'latter‘latter may represent replacemeqtsreplacements of asbestos veinlets.Veinlets...... I 32

ChemicalC'ltenricaf compositionconlgosiliol~andnrrd mineralogyntirtcmlogy of IIIctltc ranyncsire.-~everalite.everIIIagIIcsI‘Ie.—Severa.1 partialpartiai. anajyst3analyses of the magnesite are available and are arc quotedquotcd below: —- I 11I! 111III IV V A B - . % X7t- % 'XI76 'x'76 % % SiO,5i0._. .. . . -— 2.48 10.75 0.29 -’T 0.43 -—— . AI,O,AI,0, .. ,0.l90.19 0.71 .O.IS0.18 . -— -— 0.10 Fe,O,Fe.O ...'.. ) "3‘IS8I 0.28 0.64 0.280.28 — 0.06 }) 01° MgO . . .. 40.36 -— - -— -— 46.28 47.10 MgCO,Mgco, .. . --— A., 96.41'96.41‘ 86.07 97.47 --- -T —- CaO .. . . 3.39 -— . -~—_ -—- 0.62 -—- 0.40 CaCO,Caco, .. __- 1.02 1.89 0.29 —-- -— —- Moisture ,.. . —- 0.36 0.14 0.060.05 —- -—- —-- P,o,P,O, ...... ——- nil nil nil ——- -—— —-- . 0,, ...... ——- —- —- —- —-- 51.72 52.90 ZosolubleInsoluble .-. . 8.8.022 -—- —- -— —- -—- trace A'- .- - ---

Totals .... - 100.74100.74'1QO.20'100.20 100.09'.100.09 I —- 98.49 ,‘ 100.50

I. A grab sample. The MgO content is equivalent to 84.84.3939 per cent.cent MgCO,, and » the CaO to 6.41 per cent'%aCO,.cent CaCO,.‘ , 1].II. Grab sample from an adil.adit. Analyst,Analyst. C. S. Hitchen. ‘ III. Sample from quarry on south side of hill. Analyst, C. S. Hitchen. ~uchMuch of the silica is present as encrustations and Inin druses. IV. Sample from upper quarries. Analyst, C. S .Hitchen. Y.V. Sample from Kinyiki Hill, exact locality unknown. A. .Magnesite, Transvaal. Quoted from "‘Magnesium,'"Magnesium, magnesite andand dolomite'f, dolomite^, . Imp. Itlsl.Inst. Rep., 1939, p. 51. ... . ' B. Mysore magnesite, "trade“trade sample".sample“. Quoted from I'bI'd,,ibid,, p. 64. Hitchen judged from the samples he analysed that silica in an “inherent""inhereds state usuallyusua'lly constitutes less than one per cent of the ore, the remainder being quartaorquartzor chalcedonicchalccdonic silica in veinlets, encrustationsencriatations and vugs. Later he formed the opinioaopinion that much of the ore would be found to contain 10 to 15 per centccnt of silica, but believedtielieved it coirldcould bebc reduced loto 6G to 8 per cent by cobbing and suggested that it could bcbe decreased generally .to'to 3 perpcr cent or lessless by flflotation.otation. Operators have been inclined to consider the presence of silica as a surface phase that would disappear as the hill was pierced. This, however,however, .. is unlikely—éhemimlunlikely--chemical considerations indicate that some silica must be expected, though portions of course may have migrated in solution. The reaction leading to the formation of the magnesite may be conveniently expressed by thethe‘ simplisimplifiedfied equation:—equation:- ‘ MgSiO.,MgSiO + C0-CO, = . MgCO,M&O, + SiOz magnesium olivineolivinc +.+ carbon dioxide = magnesite + silica. By selective working parcels a€ magneaitc have been extracted from the. deposit that.that‘ By seleclive working parcels of magnesite have been extracted. from the. contained 3.5 per cent SiO_SiO, or less. . Prod11criorr.-RecordsProductioIn—Records indicate that ubol~tabout 327;327;. tons of Kinyiki mamesitemagnesite has been shipped or sold, though it is certain that considerably largerlarger'tonnagestonnages have been taken . from the ground in attempts to obtain supplies conforming with ,high-standardhigh-standard and - rigid specifications.specifications. In 1940 theIhc price realized was Sh.Sh 55 per ton at the coast.coast The total value of production is not known,. but Isis probably of the order of £1,300.f 1,300. Serious production ceased in the early part of _ 1941. APPENDIX 1"1Y Owen MINERAL Darosrrs AT KINYIKI b—AsbestosI.-Asbestos Several veins of asbestos have been foilndfound inIn the dunite of Kinyiki Hill. They ramify - through thethc intrUsiveintrusive and consist of two main_types,,main. types, (a) irregular deposits withwilh irregularly arranged shortshort' 'fibresfibres and (b) cross-fibrecross-fibre veins with long fibredfibred asbestos. .q

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4 33

TheThc latterlatter are are ofof lessless frequentfreqircnt occurrence.occ~~rrcicc.andand are arc bestbcst seenscen onon thethe south-westsouth-west fl flankank "-e".- hill.hill. FibresFibres asas muchmuch asas 88 in.in. inin length length have have beenbecn seenseen inin thethe larger larger deposits.deposits. wins-..iris onon thethe westernwestern slope slope unusuallyunilsually silkysilky fiRbrcsbres 22 in. in. inin lengthlength have'beenhave .been : ...-- It isis reportedreported thatthat goodgood quantities ofof asbestosasbestos suitablesuitablc forfor lagginglagging occur occur ?non theIllc suulhel'tt'slopes.suulllcrrl slopes. ItIt isis believed believed thatthat therethere areare sixsix veinsveins ofof thethe longerlonger fifibredbred material,material, usuallyusually twotwo to‘threeia ,~hrccfeetfeet inin width.width. TheThe depositsdeposits werewire examinedexamined byby C.C. S.S. HitchenHitchen inin 19361936 whowho concluded concluded that that thethe asbestosasbestos waswas formcdibyformed: hy thethe metamorphismmetamorphisni ofof partsparts ofof thethe hornblendichornblendic rafts rafts thatthat areare emplacedernplaced inin thethe dunite.dunitc. From'From chemicalchenlicnl andarid opticalopticdl teststests heIle identiidentifiedfied thethe mineralmineral asas thethe amphiboleamphihole anthophyllite.anthophyllile. AtAt surfaces~lrfaceitit isis frequentlyfrequently replaced replaced byby magnesite,rnagnesite, andand HitchenHitchen believedbelieved thatthat thesethese magnesitemagnesite veinsveins withwith relictrelict cross-cross-fibrefibre structurestr~lcturepossiblypossibly representrepresent originaloriginal asbestOsasbestos veins,veins, perhapsperhaps ofof chrysotilechrysotile variety.variety. ChemicalChet~iical('otttpost'tion.—One~o~~iposiriotr.-One analysisanalysis ofof thethe mineralmineral isis availableavailable andand isis quotedquoted belowbelow beside beside a a comparativecomparative analysis.analysis. .. - , . . l1._ AA ' .l’erPer centcetif PerPcr centccttl SiO3SiO, .....‘...... - ...... , 48.7248.72 56.1656.16 16.1.0aA120, '...... ' ...... '' 0.760.76 2.652.65 - Fe:0JFezO, ...... 7.057.05 .—. - ‘FeOFeO ...... n.d.n.d. 14.1314.13 : . Mn0..MnO ...... trace,trace. 0.910.9 1 M30MgO ...... ‘...... 27.2327.23 23.19 23.19 Ca0'..CaO...... -...... , .... 4.934.98 1.511.51 H,OH20 ...... n.d.n.d. 2.382.38 LossLoss on on ignitionignition ...... _ . 10.8210.82 —- - - TotalsTotals ...... 99.56:99.56' _ 100.93100.93 . -t -

I.I. Asbestos,Asbestos, Kinyiki.Kinyiki. Analyst,Analyst, MissMiss A.A. F.F. R.R.-Hitchins, itchi ins, GovernmentGovernment ChemistChemist andand I Assayer.Assayer. (This(This analysisanalysis waswas incorrectlyincorrectly statedgated inin thethe AnnualAnnual ReportReport 'ofof thethe MiningMining andand GeologicalGeological Department.Department forfor 1936.1936, wherewhere (p.(p. ‘25).25) silicasilica 'was'was quotedquoted 1010 perper centcent inin excessexcess ofof thethe correctcorrect fifigure,gure, andand FeFe waswas quotedquoted asas Fe,0,.)Fe,O,.) A.A. Anthophyllite,Anthophyllite, Kong-sberg. Kongsberg. QuotedQuoted fromfrom Dana Dana “System"System ofof Mineralogy",Mineralogy", sixthsixth edition,edition, 1892,1892, p.p. 385,385, analysisanalysis No.No. 2.2. FromFrom thethe analysisanalysis itit mayniay bebe judgedjudged thatthat thethe samplesample usedused waswas contaminatedcontaminated byby magnesitemagnesite i oror dolomiticdolomitic material.material. ' ConductivityCotiductivity n.d.—Therest.-The KenyaKenya and and UgandaUganda RailwayRailway conductedconducteb anan insulationinsulation testtest on.asbestoson. asbestos fromfrom Ki‘nyiki Kinyiki inin 1935.1935. UsingUsing 2525 perper centcent limelime asas aa bondandbond and canvas canvas . wrappings,wrappings, aa steam steam pipe pipe (4} (4f in.in. diameter,diameter, 4646 in.in. longlong and and lf in.in. thick)thick) connected connected byby aa l1 in.in. coppercopper pipe.pipe, 1010ft. ft. 44 in.in, in in length, length, toto aa boilerboiler underunder aa constantconstant pressurepressure.of.of 105105 lb.Ib. perper sq.sq. in..'of in. of steam steam andand fifittedtted withwith aa draindrain cockcock fifixedxed onon the. the. openopen position,position, waswaS laggedlagged withwith the the asbestos asbestos toto givegive anan outside outside diameterdiameter ofof 66 in.in. TheThe temperaturetemperature inin thethe 'pipepipe farthestfarthest from from the the steam.steam entry entry waswas taken taken byby aa pyrometer‘ pyrorneter andand thethe externalexternal temperaturetemperature ofof thethe lagginglaiging byby aa thermometer thermometer suspendedsuspended ._1f in.in. fromfrom thethe pipepipe lagginglagging andand protectedprotected fromfrom draughts.draughts. TheThetest test waswas repeatedrepeated with with thethe pipepipe unlagged,unlagged, thethe thermometerthermometer beingbeing loweredlowered to40 thethe samesame distancedistance fromfrom the the pipe.pipe. TheThe resultsresillts obtainedobtained werewere as'as' follows:—follows :- i . ' ThermometerTlrernion~eterreadingsreoditi~.~ PyrometerPyrotneter reading:readings °F.OF. - . °F.'F. (a)(a) withwith lagginglagging ...... 97'97 _ ‘ ; 275275 (b)(b) withoutwithout lagging lagging ...... - 144144 . , 265265 Production.—TheProdrrcrion.-The bulkbulk ofof .the.the outputoutput hashas beenbeen soldsold locally. locally. ItisIt is estimatedestimated fromfrom .departmentaldepartmental records records that!hat betweenbetween June,June, 1936,1936, andand thethe end end ofof 1939,1939, approximatelyapproximately 8080 . VlOns'weretons were produced.produced. BetweenBetween the!he latterlatter partpart ofof 194]1941 andand thethe earlyearly months months of of 19451945 ProductionProduction waswas considerablyconsiderably increasedincreased andand recordsrecords indicateindicate anan outputoutput ofof aboutabout 800800 tonstons . 0‘ powderedpowdered asbestosasbestos andand 2424 tons.tons ofof asbestosasbestos Wool.wool. ’ ‘ 34

II—Quarlz Quartz of two kinds has bccnbeen workcdworked on.Kinyikion‘Kinyiki Hill—~massiveHill-massive quartz and quartz crystal for piezo-electricpiezo-elcctric purposes. The former has been derived from the pegmatitcs that cut the soilthernsouthern part gfof the hill. Itit is estimated that the production has been of the order of 95 tons;tons, all of which has been consumed locallylocnlly for ceramics purposes. Pieza-electricPiezo-electrie quartz was discovereddiscovcrcd at Kinyiki by a prospectorprospecior in 1936 while pitting gravels underlying three to six feet of red soil on the west flflankank of the hill. (See Annual Report for 1937, p. 29.) A remarkably perfect crystal. about 2f Ib.lb. in weight, was unearthed and forwarded to England, where it was reported to be of very good quality. The deposits were examined by C. S. Hitchen who concluded that they were water-borne gravels and that the source might be some distance away. Prospecting continued below the hill and it was found that possibly usable crystals were of rare and sporadic occurrence.Occurrence. A second large crystal was fou'ndfound and on examination in England was stated to be free of electrical and optical twinning and internal fractures and as good as medium quality Brazilian material. This crystal was 9 cm. high, 6.565 cm. diameter, and weighed 825 grams.grams.- Plates cut from it gave excellent results.

It became necessary to definedefine the sburce of the crystals, and in February;February, 1938, the deposits were re-re-examined-examined by W. Pulirey'whoPulfrey who concluded that the gravels are not water-borne, but eluvial, and that the quartz crystals are derived from quartz-richquartz~rich pegmatite veins, one of which was located by trenching.trenching In I940,1940, a further examination was carried out by Dr. Parkinson. He found that the crystals occur in a restricted area on the low ground at the western foot of the hill and are derived from latevhydro-late hydro- thermal quartz veins that have been deposited in fifissuresssures in the Basement ,System,system rocks. Extensive work was carried out in the search for workable deposits fi$eludingicluding thethe. clcaningcleaning of old trenches and the excavation of more than 46,000 cu. tilt@ of ground. St~bsequentlySubsequently three cross-strike trenches were dug and as a result two moreWre sv‘eins>veins ofd quartzosequartzose‘ pegmatite were uncovered. Pits were sunk in the three veinaeknown,veinsknown, but the two southernmost petered out at shallow deplhs.depfhs. Attention was themthen>concentrated on the northern vein and three shafts were sunk on it to depths of 32, 22_and&? and 212| ft., and connected by about 120 ft. of driving at depths of 20 to 30 ft. In al‘b'alN3.0003,000 cu. ft.It. of'of ground were excavated but no pockets of quartz crystals were found.foud. The wo~kWork ' showed clearly that the pegmatites arearc invaded by later quartz veins, jcontainingmntaining in places epidote and chlorite, and presumably of hydrothermal origin. The hydrothermalfiydrothermal nature of the crystals recovered is perhaps also indicated by the fact that some of themthein were found to be naturally etched. Though nolcrystalsno‘crystals Werewere found in the underground excavations,excavations. a parcel of 17 Ibs.lbs. of crystals was decovered{ecovered from a portion of the collapsed ._ outcrop of the same vein. Work was discontinueddiscontinded in 1942.

. 'Producrion.—ItProd[rcrion.-It will be obvious that. the production has been small. In addition to the two crystals mentioned abovehproductionabove, .production included: (1)a(l)a finefine crystal weighing 2 kilos. that was retained by claims operator; (2)(Zia a parcel of 12[2 crystals with weights ranging from 580 to 149I49 grams (June, I938).1.938). . Of these, three only wereWere found to be usable.usable but it was noted that from the 14 crystals submitted by this time. time, fivefive had proved usable—ausable-a ratio comparable with that found elsewhere; (3)(3)a a parcel of 26 crystals shipped in 1940. The largest of these.weighedthese .weighed 18a}18+ 01.,oz., 16fl6+ oz. and 13flli or.oz. (approximately 524. 467 and 382 grams respectively). All were found to be relatively free from optical twinning and in most cases without serious electrical twinning;twinning: (4.a(4)a fourth parcel of 26 crystals.crystals totalling six kilos in weight, shipped in 1941.19!“. . They included a crystal of 2,084 grams weight which. however, was too flawed 12to be.ofbe of use. The bulk of the remainder were-of.smal1were‘of‘small size, but several of them were found to be remarkably free from twinning, and were stated to be of-of. quality equal to the best BrazilianBmzilian material. Ten crystals from the parcel were fotrndfound to be about 100 per cent useful for pe'izo-electrical purposes.'purposes.‘ . 35

Ill-Ill—Felsprir Felspnr 3 Fclspar has beenbecn sporadicallyspor;rdically worked in the pegmatitepcgmatite lenseslcnscs that cut thcthe southernsol~thcrn'7‘ part of Kinyiki HillHill. Occasional spccimcnsspecimens that have been examined in-in thinthin section proved to be microcline-microperthite.microclinvmicropcrthite. It has also been recorded (Annual Report for:for.“ 1936,l936, p.p.25), 25), hOWever.however, that cleavlanditecleavlanditc (a lamellarlamcllar variety of albite) ISIs developed in thethe- outeroutcr ielspathicfelspathic zones of some of thethc pcgmatites.pcgmatites i

Production—RecordsProdrrc(ioti.-Records indicate that approximately 115“5 tons wereWere produced between"between October, 1943. and March,March 1945.I945. It is believed that the whole was consumed locally for:?for-'3'ii B'

I:

ceramics purposes.purposes '4‘~’

11‘3”.“4 IV— Ve‘rmic”lite I Itit waswas early recognized that deposits of vermiculite are associated with the other'$other‘l minerals of Kinyiki Hill. They occur in two forms (a) the less valuable,valuable. as large:large; plates of-of vcrmiculitized mica in the pegmatites and (h)(b) as veins and pockets in most}most!: of the magnesite and asbestos workings. The latter are closely associated with the raftsfraftf' and xenoliths of hornblende-schistshornblende-schists enclosed in the dunite,dunite and presumably OWeowe their origin to metamorphic and metasomatic action by the dunite.d11nite. They are stated to bebe; well developed on the southern side of the hill. -

Samples from the deposits were sent in 1937 (At~nual(Annual ReportReparr farfor 1937, p.P. 25) 10to' London and it was reportedreparted that they were equal in quality, when cleaned,cleaned to material then being imported from the U.S.A. and Russia.Russia The samples were crude material - and had not been treated or benebeneficiatcdficiated in any way inin' Kenya. Tests on them gave the following resultsresults: :—--

. SattrpleSample A ' SantpleSample B SanipleSample'C ' C Crude,rude, weight in lb. . - per Cri.cu. /I.ft. . ‘ ... . _ Undried ...... -. . 42.5 Almost no moisture MoistureMoisture. . '! . 1.2 per cent

,. . Dried ...... 40.5 40.67 ‘ .~ 73.17 ' E-rfoliafed,Erfolzaled weightweigh! it1in lb. per crr.cu. fi.fI.. . . 8.8 7.147.!4 16.25I625 ., It was considered that by treatment the bulk density of the exfoliated produetprodlnt couldcoilld .- I be improved by a1at least one pound per cu. it.ft. . .'?. ti"-. 8 In 1944, more tests of the material Werewere carried out in the laboratory of ~h$mg Mining and Geological Department.Department Again crudecri~dcunprocessed material was used for thtthy.l tests. The bulk density of samples inclt~dingincluding +}+ f in. material was found to be 77j77} {$5tfir 78j78} lb.Ib. per cucu. ft.ft and excluding the +-.l+ f in. fraction,fraction. 68+68j lb.Ib. per cu. ft. The moistur‘moistuf content was 6 to 7 per cent corresponding with dry bulkbulk. densities of 63+63j to 64+64j lb. pyperf cu. ft.It. The —l-4 in. fraction,offraction of the sample when screened yielded the following results.results:+4?.“-

Screen. Weight. % :

. , +20 mesh LMM. . . . . 27.4 (dry(tlry sckwnin,:screening of air drieddrictl snmplc).samplel. -—2o I.M.M. +30 ,. 13.8. . 1313.11 ' ' f —-30 13.8. +12II ,, 13.3.. 42.2 —,120 as 17.2.172

99.9 I | The coarsest grade was found to contain somesonle magnesite and dunite grains and the -~30 30 mesh grades contained much olivine, magnesite,magnesitc. anthophyllite, etc. The finestfinest grade incorporated 30 to 40 per cent of such impurities. 36

The cn~decnlde sample and fractions screened from it wcrcwere expanded in a mumemuffle furnace at a temperature of I,OOO0C.1,000'C. Periods of ten minutes wcrewere allowed ‘forfor each heating, which was cirtainlycertainly far[in in excess of the optimum exfoliation peribd.period."l1Ie The ex- foliated products were gently screened, the results being as fol10w~:-follows:—

SanrSamplr plc .Bulknulk Density ' Screet~Screen Grading ‘ .

Ih.lb. per r~t.cu. ft.II. + 20 -20 4-+ .to m -—'30 30 + 120 - 130no Turn1Tum! Total ...... 17l7 63.2 17.8|7.8 17.4”.4 itsI. 100.0l00.0 -4-4- in. + 20 mesh ... . 13-174I5—I74 " 25.8 ’ 17.3”.3 44.6 12.0 99.7 ._-—- 20 .t.—l- 30 ,... . . 18I8 28.128.] 54.0 15.4l5.4 1.8L8 99.3 -30+120— 30 +120 3,,. ... . 21 g Q50.5 8.2 . 88.3 2.6 99.6 -— 120 ,,.. . . 25925% 0.2 0.4 29.9 . 69.2 99.7 meThe -30 mesh material consisted in all cases mainly of thin flakesflakes or non-micaceous mineral. Expanded flakesflakes had a bisc~~itbiscuit colour with silvery reflections.reflections.

Prodrrcriot~.-ThePradIIerI‘on.—The total outp~~tputput of cr~~decrude material. has beenbee'n of the order of 25 tons. ,

V--Corrrti~l~r~trV—Corm'ulmn am]a~rd SapplrircSapphire The ,discoverydiscovery of corundum at Kinyiki was announced 'in the Annual Report for 1936I936 (page 26). Itit was found as surface blocks on the west side of the hill. Subsequently when soils and gravels from excavations were being washed gem-quality sapphires. derived from disintegrated corundum crystals, were obtained in small quantities. Inin I939I1939, in.in a pit sunk on the western contact of the dunite,dunite. carundumcorundum was found in sit'u.situ. Itit occurred as a nest of long hexagonal crystals with gently curved faces, associated with vermiculite,vermiculite. ilmenite and granular hornblende.hornblende, and may reasonably be ascribed to the desilication of the schist wall-rocks by the dunite. oneOne of the crystals was about three feet in length. RareRare‘ small patches of sapphire quality were found inside the crystals when they wereWere broken open. The corundum crystals were considerably intergrownintergrOWn with cortmdophilitecorundOphilite and pink margarite.margan'te. Other occurrences of co~ndumcorundum might be expected atat‘the the extensive dunite contacts ‘ I on the hill-bothhill—both at the major contact and those of the numetousnumerous xenoliths. Large plates of corundophilite have indeed been found some distance away from the known » occurrence of corundum, and suggest other depositi.deposits. Itit is probable, however, thatthat any deposits found will be of small extent. It is likely too,too. that sapphires would not be recovered from corundum .depositsdeposits in situ, but only where,naturalwhere natural disintegration and cleaning has haq liberated gem fragrneritsfragments and allowed .themthem' to become part of eluvial deposits. ProduclianProdrrction.-The--The production of gem sapphires in 1937 anc!and. ‘9381338 realized £236.E236.

Vl—Miscelianeous Minerals Copper.-TracesCopper.—Traces of copper in the form of carbonate staining have been found inin. the schists around Kinyiki Hill. Itit appears to have no economic significance.significance. Begy1.--CrystalsBeryl —Crystals of beryl have been reported as occurring in the pegmatites (innual(Annual Report for 1.936,1936, p. 25). They are presumably of occasional occurrence only. 1lmenorurile.-HitchenIImenoruIile.—+Hitchen has recorded"recorded (Annrral(Annual Report for 1936, p. 26) the presence of eluvial ilmenorutile on the lower western slopes of the hill. ‘ Uvarovire (Chronre(Chrome Garner).-SomeGarner).—Spme years ago, Sir EdrnundEdmund .TeakTeale found a small fragment of uvarovite'onuvarovite on Kinyiki Hill. So far as is known this isIs the only record of the occurrence of chromium minerals there. . . 37

APPENDIX V MICA Mica has been workedworkcd inin pegmatites pcgmatitcs near Rhodesian Hill inin thethe Tsavo ValleyVallcy and nearnear Mgange Camp. north-west of thethe Taita Hills. 1.I, Rhoda-rid"RlinAcrinrr Hill.==C.laimsffi/b<.laims were peggedpeeecd inin 1938.1918, buthut apparentlyepnerentlu littlelittle work waswaa carried out-untilout until 1940, while no production was recordedrecorded until 1943. During thethe 12401940 prospecting two opencastsopencasts were excavatedexcavated and micamica samplessamples fromfrom themthem were pronounced jj by London authorities as of goodgood quality. quality. At depths depths of threethree feetfeet mica 'waswas foundfound toto bebe [ plentiful and inin largelarge books,books, but usually Weathered. weathered. In 1943,1943, assistanceassistance renderedrendered byby thethe ' Mining andand Geological Department, ledled to to thelhe discovery of another pegmatite containing ' pockets of rubyruby mica.mica. ItIt was Provedproved over a strike ofof 50 it.It andand thethe mid:mica pockets were : foundfound at aa depth of 10 ft.ft. OnOn anotheranother pegmatite,pegmatite, selvages selvages ofof micamica were were found found ranging ranging fromfrom 11 in.in. toto 1212 in.in. inin ' width.width. TheThe micamica was was palepale green green andand reasonablyreasonably freefree fromfrom spotting,spotting, thoughthough muchmuch waswas - badlybadly striated. striated. TheThe pegmatitepegmatite was was excavatedexcavated overover a a distancedistance ofof 150I50 ft.fi. byby thethe Govern-Govern- 1’ mentment ProspectorProspector andand toto ,aa depthdepth ofof 1515 fift.,t, butbut thethe micamica atat lowerlower depthsdepths waswas foundfound toto bebe , striatedstriated andand more more spottedspotted andand stainedstained than than thethe surfacesurface crystals.crystals. TwoTwo parcelsparcels ofof micamica submittedsubmitted toto thethe Ministry Ministry ofof Supplies'Supplies' purchaserspurchasers 1nin 19431943 werewere '_ gradedgraded asas follows:follows :-- . . Firs!First consignment,co~rrig~rrr~e~~t, SecondSecond camignment,coruignment, SizeSize gradegrridc approx.approx. wt.wt. perper centccrlt ' approx.approx. wt.rut. perper centcent

22 .';...... a.. 22 ..: . - . . . . — ’ ' 33 ...... 55 ...... 1.5' 44 .... .'. . . 8 C . 7 u. . . ‘7.4 ' 55 ...... 20 ' ...... 14.5 515+ ...... s ...... 511.6- 66 ...... 45 .. 46.5 77 ...... 10 14.1 ThinsThins ... . ’ . . 5 ...... —-

ThinsThins andand unspottedunspotted -

cleaningscleanings ... . —~—- ...... 4.34.3 -.;—* .,

rmy

TheThe fifirs1rst consignmentconsignment waswas reportedreported asas containingcontaining muchmuch spottedspotted andand greengreen micamica withwith :, as“:

smallersmaller proportionsproportions ofof brownbrown andand rubyruby type.type. TheThe laterlater consignmentconsignment contained contained a a goodgood -. proportionproportion ofof rubyruby mica.mica. Production—FromProdrtclion.-From recordsrecords inin departmentaldeparlrnental fifilesles itit. appearsappears thatthat productionproduction beforebefore 15- November,November, 1943,1943, waswas aboutabout 120120 poundspounds of of cutcut mica.mica. BetweenBetween November,November, 1943,1943, andand March,March, 1945,1945, workingworking waswas sporadicsporadic and and aboutabout 560560 poundspounds ofof cutcut micamica werewere sold,sold, the?the totaltotal valuevalue beingbeing aboutabout Sh.Sh. 1,900..1,900.. OneOne consignmentconsignment realized realized anan overalloverall priceprice ofof Sh. Sh. 4'4 perper j pound,pound, butbut thethe estimatedestimated averageaverage forfor allall consignmentsconsignments was was aboutabout $11.Sb. 3/503/50 perper pound.pound. 22. Mgange.Mgange.-A—-A singlesingle prospectorprospector workedworked mica mica inin pegmatitespegrnatites duringduring 19441944 nearnear MgangeMgange Camp.Camp. Production Production waswas smallsmall butbut the the micamica realizedrealized pricesprices in in excessexcess ofof thosethose' obtainedobtained forfor.mica mica fromfrom otherother localities.localities. AA bookbook sentsent toto thethe purchaserspurchasers forfor anan opinionopinion weighedweighed 2222 1b.Ib. andand yieldedyielded 31}3) lb.Ib. ofof cutcut micamica (an (an extractionextraction ofof 1717 perper cent)cent) ofof goodgood stainedstained rubyruby micamica typetype thatthat realizedrealized moremore thanthan Sh.Sh. 99 perper 1b.Ib. TheThe remainderremainder ofof thethe bookboo& waswas cross-grainedcross-grained andand describeddescribed as as useless.useless.

TwoTwo subsequentsubsequent consignments consignments ofof (1)(1) 1616 113.14lb. 14 oz.oz.. andand (2)(2)' 125I25 'lb.lb. 3}34 oz.oz. ofof cut;cut:; ! micamica yieldedyielded Sh.Sh 178/94178194 andand Sh.Sh. 1,087/571,087157 respectivelyrespectively-(i.e. (i.e. approximateapproximate averagesaverages of;-of-; Sh.Sh. 8/708/70 andand Sh.Sh. 10/5010/50 perper pound).pound).

. .

'2 38 The'the gradinggradings of the Motwo consignnientsconsignments werewerc as follows:—follows:- Cnnsigmncn!Cnttsigt~trrrttf Il . '- Cur~,rig~~ri~e~rtConsignment 2 PrrPer cct!fcent Per cent Extra specials ...... , , -—— ...... l.l1.1 ' ' Specials ...... 4 -—- ...... 0.6 ...' Il -- ...... 11.9ll.9 ...... 6.4

2 ...... 24.12-H .. 0...... 13.7l3.7

3 ...... ".14.8' 14.8 .. .'... .. 'j9.3, 9.3 . 4 ...... 17.4I7.4 ....-..'I. .... 18.l18.1 5 ...... 10.4 ...... ”21.2' 21.2 5St ....._ ...... 2.9 ' ...... 9.6 6 ...... —- ...... 7.5 Thick thins ...... (3-5) 12.5 .... .: '* (3-6) 6.0 Thin thins ...... (3)3 5.9.5.9 ...... (3-6) 6.4 FS.ES...... —--...... 1.5 .-G.S. G.S...... l0.010.0 . . , .-‘...... 24.9'24.9 \. S.s. ...; ...... 30.7 ...... '. .. 17.3 H.S...... ' ._... 40.7 ...... ‘ .... 43.343.8 Thick thins ...... 12.6l2.6 .....' .. . . 6.0 Thin thins ...... 5.9 ...... ' 646.4 It will be noted that the proportions of sinsize grades was more than usually biased3owardsbiased-"towards larger sizes. The pegmatites were not carefully explored and it‘it'isis considered that the prospector closed down prematurely. The total value of mica obtained from the pegmatit‘epegmatik during the short Limetime it Was was worked was aboutaboitl Sh. l1,300.7-300 t . APPENDIX VI ' . MISCELLANEOUS DEPOSITS 1. Liti~e.rtone.r.-TheLI'IIIe.rtmIes.—The various occurrences of crystalline limestones are described in Dr. Parkinson's report. In addition there artare depasitsdeposits of kunkar limestones at several localities, especially south of the Taita Hills.Hills, near Makindu, and east of Kinyiki;Kinyiki‘. It is believed that limestone from the.Mvlakinduthe-Makindu deposits will be used for the preparation of lime at Kinyiki. . 2. Clays.——-ClaysClays.--Clays suitable for the manufacluremanufacture of bricks and tiles have been dis- covered by Markham dc& Co., in the MtiloMtito Andei area.area:In I-n the past clays near Voi were used by the B.E.A.RM Corporation for the manufacture of mangalore type rooroofing.fing. tiles. They.... were reported to be of good quality. . . _ 3. PoseRose Quartz.~uarfr.-~'p&matite—A pegmatite containing rose quartz wasw& found several years ago north-westndrth-wcst of Tsavo.TSavo. So far .asas is known no produdi??production was made...... 4.4. Copper.Copper.--Capper—Cppper carbonate. staining has been noted.innoted in se~ralseveral places northnorih.i"dand south of the RiverRiVer Tsavo near Tsavo.Tsavo it appears prohableprobable that the carbonates are deriVed'dt~ived from chalcopyrite contained ia.pegmatites.in -pegmatites. '.'. '5s Kaolin.~iroliri.-~weiveL—Twelve 'deposits of kaolin.kaolin .werewere discovereddifcwCred, :gridand mapped inin. the hills . a .@wf‘e'w_ 'miles'mild 'WestWest of Ndi. They arcare difcontinuoysdiscontinuous and scattered over a .highlyhighly &odede‘rdded ' arearea a little’litt1e"inore'thanmore 'than one square mllcmile inin- extent. Other occurrences we*,were notednot+ in the‘the hiHshills further west. - ...... Inipectidh.~.bfInspections 'of sampleisamples showed that, in mostmosl caseSJh'qcasli,?~i.kaolinkaolin has bee'nbee" dCrivedderived fromfrOm the decomposition of para-gneisses and schists',schists; and, in somesome-.instahccs;-.perhaps"insta'nces', perhaps from granite. The .prospectorprospector :foundfound that some of the deposits are underlain by red clay and earth;earth and it appears likely that SUChsuch'.occurrenccsoccurrences pre..slipp'cdare slipped masses. The .kaolinkaolin itself was not typical of redeposited material. .. -. . . 39

~radin~Grading anaIysCsanalyses showed lhatthat the kaolin varies considerably from deposit to deposit, ... viz.viz.:— :-

NIII~Numberbez SandSum! . of Moist.“ re + 60 it.Fines. l(eolir~.Kaolin. TOTAL. ICEMARKN.Reunite. or h1oisbr11-c +GO I r Deposit. "/,% 1nes11mesh ' ‘ ‘

% - . . -e- 1 ,

I v.1" 1. -— --— -— '— a‘I -— ' VcryVery impum.impure. f 3.2. 1.3"1.3 66.155.4 . 10.930.9 ,.. 1 i1.811.8 00.499.4 Off-whib.Off-white. Derived from 8 - I p~uascllist.paraschist. ', 3. 0.5 63.6 25.0 10.0 00.009.0 ' PnloPolo buff. DorivdDerived lro~llfrom 2 coarsocourse gneiss. Quartz C:, Tins-131mg; iiron-stained. ron-shined. i' 4. 0.9 60.050.9 32.632.5 15.6.15.5 1| 99.8 ' Urownish-buff.Brownish-bufi. UerivwlDerived 3mam . -' ' from paregneiss.paragneisa. - i:' i Quartz non-stained.non9tsined. .-' i . . -5.5. -——' ‘ -— -—— -—- I -— Very impure. 6. . 1.6 49.0 31.631.5 17.1 j Q0.290.2 White.\Vhite. Derived from ., - ‘ ' . firanitogranite or granitoid :L I gneiss.gneise. 7. 0.6 88.068.9 44.024.9 5.6 i 1~0.1)100.0 Wl~ite.\Vllite. Derived from. . I parognciri'i.parugneisi. _‘ .. . 8. 1.3 133.8153.8 . 24.02-1.0 10.7 09.899.8 Pinkisll-buff.Pinkisli-bufl. ~crivilDerived . from com-soccrarjo pink ,' . - . granjtegranite or gncisu.gnoiss. 0.9. 1.8 61.7 22.622.5 13.7 1 09.799.7 Off-wh~te.Off-white. Derived from . 1: ‘ coersecoarse granite or '_ panitoidgranitoid gneiss. 10. 0.60.5 61.8 29.9 . 7.G7.6 1 '09.899.8 White.VVhito. Derived &omfitom ;', : ‘ .. paragneiss.pnmgneiss. ' 11.ll. 1.1 60.560.7 28.523.5 9.09.1) , i $9.209.2 PalePelebu buff.fi. Derived tidmfi'om ' . - ' . p~~qneis.paragneise. 12. -— -— -— -— I-i — Pink. Very impure: - To test the refractory qualities of the various sa'mplcssamples small cylinders of the "fines'.'"fi'nes'-'

obtained were made, thoroughiythoroughly dried, and then firedfired in an oil furnace.furnace, maintained at .

_ ‘

1,400eC.1,.400’C for several hours. All the test-pieces proved to be refractory at that temperature,temperamre - = . and yielded generally white or mottled "biscuit'“biscuit types of refractories:-refractories: —— ., .. Deposit No. 'ResuItRead: ‘ i'. 2 . . . . . Buff.Bufl'. Medium sGengthstrength "biscuit"“biscuit" type. . $ . $rmmnm

3 . . . . . White. Stony, due to incipient fusion. .$fl iiwr 4 .. . . Mottled. Medium strength “biscuit" "biscuit" type. Vi h 6 .. . . White. Medium strengthstrength"'biscuit" "biscuit" type. . , , 7 .. . . White. Soft "biscuit"“biscuit" type. ' k 8 .. . . White. softSoft "biscuit" type.:type; . . 9 .. . . White. Medium strength ”biscuit" "biscuit" type. 10 .. . . ' Light grey. Hard stony type. 11 .. . . Mottled. Medium strength “biscuit" "biscuit" type. . , .40 _

ADDENDUM MmznALM~ERU ~ODU~ONPnonucnox FIOURERFmimzs FORrun THRrun Mmo-ANDEI-TFIAVO.Mme -ANDEPT8AVO AREA SVUYEQUENTSunsuqunu'r 1‘0TO THE COMPILATIONCommunion orOF mTtlP: RE~RT.Enron-r. THI~Tm: qnzsFICIURP,S ARE BAHEDBump ON0N DEPARTMENTALDennizna-AL RETIIRNRETURN RECORDSEsconns

Mineral- ' Period- Quantity ' AproximnktAproximnm Mmaral . . Del-nod Produced I ,. Value . ‘ _ . . Tor18Tom .~ 2%.:S'li. Asbestos ... . June--December,June—December. 194519-15 ...... ' - . . 8,2158.215 . '‘ 1946 .. . . .'; Powder . . 17-40 2,62,516 1ti -. .- Wool . . 2.602-50 . 908 JJanuary--June.sunny—June. 1947 . . PowderPowdex . . ' 6-766-75 - 2,1452.145 - ' '_ . Wool . . 2-50 812 Grap11it.cGraphite -:‘ . . October. 19461945 . . .. 1.501-50 -_ FclspsrFclspar .. . . 1945 _ ...... ' 108.00103'00 ' 7.0207,020 - . ~ 1946 ...... 13.0043.00 . 2,808 Kya~lito*Kyanite‘ . . 1945 ...... - .... . 444.00 .1.6Z4x.1,62a L1 ' 10461946 ...... , 2.380002,350.00 9,426x9,42S'£ . - January-Aup~~qt,Janumy—Augmt,1947 1947 . . ". .- 9,777'009.777.00. 781.600 AIsgneviteMagnesite .... . - JJune-December!uric—December, 19461945 ... . 14-30 1.1201,120 ' 1946 ...... GO-OOt60-001" 13,46013.450 . Januuy—Jmle,JanuaryJune, 1947 ...... 40.3640'35 3,280 Pegmatite.Pegmatite ... . JJune-December,une—December, 1946,1945 ...... 10.0010-00 660650 1946 ...... 20.002000 1,300 Quartz . . . . JJune-December,une—-December. 104G1046 . . . ' 96:OO96:00 -. 0.2406,240 1946 ...... 136.60135'50 8.8248,824 VermiculiteVermiculitc . . Jime-December,flaw—December, 194619415 . . 10.0010-00 . 750 ' 1946 ...... 0.600'50 89 _

t"f The percentagepcrcentRgc distribr~tiondistribution of thothe kynnitckyunite midsold bet\vernbet“ eon JsnueryJanuary and August.,August- 1947 was cisas follow?,follows *-:— U.S.A.,U.S.A.. 64.954H9 ;, U.5..1.1.5., 23.723-7 ; Ddgium.Belgium. 13.213'2 ; Frmicc,France, 3'03.6 ; Austruliir,Australia, 1'51.6 ; Palastine,Palestine, 1-5;1.6 ; hctll.Local, 08;0.8 ; Holland, 0.7.0-7. .. .- t1’ Includes 10 tomtons calcincdcalcined megnesite.'magnmite.