Field guide diamonds 06 re edited-for_checking

1. 1
Diamond DEPOSITS
Mike C.J. deWit
Tsodilo Resources Ltd; University of Pretoria
Gary Dorkin
Rockwell Diamonds Inc.
Dave Morris
Archaeology, McGregor Museum, Sol Plaatje University
Field Trip Guide Pre 6
22–27 August 2016

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1. TABLE OF CONTENTS
2. Timetable ................................................................................................................................... 3
3. Geological and geographical maps ............................................................................................... 5
4. Introduction ................................................................................................................................ 5
4.1 Background ................................................................................................................................. 5
4.2 Drainage history of theVaal–Orange basin .................................................................................. 5
4.3 Diamond-bearing gravels on the Limpopo–Vaal watershed, NorthWest Province ........................ 6
4.4 Evolution of theVaal–Orange drainage ........................................................................................ 8
4.5 Brief history of South African diamond occurrences ..................................................................... 10
4.6 Geomorphic trapsites ................................................................................................................. 12
4.7 Estimates of production of secondary deposits ........................................................................... 13
5. Stops ......................................................................................................................................... 13
6. Bibliography............................................................................................................................... 36

3. 3
Diamond DEPOSITS
2. TIMETABLE
DATE
22
23
24
25
26
27
EVENT
Depart from OR Tambo 10:00. Arrive at
Tirisano alluvial mine north of Ventersdorp
at 13:30
Visit the alluvial digging areas north of
Lichtenburg
Stops at the London run near Schweizer-
Reneke and Klipdam at Windsorton
Drive from Kimberley to the Middle Orange
River
Drive to Barkly West and Kimberley in the
afternoon
Departure from Bloemfontein to Cape Town
Overnight
Lichtenburg
Lichtenburg
Kimberley
Douglas
Bloemfontein
COMMENT
Visit several excavations to examine
the diamond-bearing sediments
These include the Manana run,
Welverdiend, Pienaar’s Pothole,
discovery monument, Malan’s and
MSG potholes
Active diamond operations in the
North West alluvial field and terraces
along the Vaal River
Visit the Rockwell operations along the
Middle Orange River
Visit to Glacial pavements and Dwyka
tillite and associated gravel deposits
at Canteen Kopje, and the Big Hole in
Kimberley

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3. REGIONAL GEOLOGICAL MAP
Figure 1a. Overview of route map on Google Earth.
Figure 1b. Simplified geological map indicating the stops.

5. 5
Diamond DEPOSITS
4. INTRODUCTION
4.1 Background
This field trip provides a general overview of the Lichtenburg–Ventersdorp, Lower Vaal River, and Middle Orange River
systems, which are the major diamond-bearing sedimentary source areas and conduits of southern Africa, draining the
high-lying (>1 000 m above sea level) interior plateau (source) westward into the Atlantic Ocean (sink). The long-lived
Vaal–Orange drainage system was, and still is, the most economically significant waterway in southern Africa, its timeline
andcontributiontomineraldepositsspanningtheLateMesozoicandCainozoiceras.Forexample,someoftheheavymineral
sandsinsouthernNamaqualandowetheirearlyorigintotheCretaceousVaal–Orangedrainage,andthebulkofthegasfound
in the Kudu field offshore southern Namibia derives from the Late Cretaceous Orange River delta. Subsequent epeirogenic
uplift at the Cretaceous–Cainozoic boundary, which persisted intermittently through the Cainozoic, rejuvenated most of this
once-mature drainage basin. Such renewed erosive activity, albeit punctuated, promoted the formation of inland alluvial
diamond placers and, along the southwestern African coast, gave rise to the richest known gem-quality alluvial-diamond
regional placer.
The Lichtenburg–Ventersdorp diamond fields, which were always believed to have been part of the Cainozoic drainage
system of the Orange–Vaal River drainage basin described above, have recently been described as being linked rather to the
Carboniferous–Permian deglacial event that affected large parts of Gondwana (De Wit 2015, 2016 in press). The sources for
these diamonds are likely to have been 500 Ma old kimberlites. Erosion during the Late Mesozoic and Cainozoic would have
reworked some of the diamonds from these secondary deposits into the post-Gondwana Orange–Vaal river system, adding
to those eroded from the large Cretaceous cluster of diamond-bearing pipes in central southern Africa.
TheKaapvaalCraton,underlyingalargepartoftheinteriorplateauofsouthernAfrica,hostsmanydiamond-bearingkimberlite
intrusions — the most famous of which is the Big Hole in Kimberley, where this excursion will end (Stop 18). Since the
emplacement of the kimberlites in the Kimberley area between 120 and 80 Ma ago (Cretaceous), erosion has removed the
upper levels of these intrusions to varying degrees (Fig. 18). Concomitantly, the drainage from the interior primary sources
hasbeendirectedwestward,intotheAtlanticOcean,viaalong-livedandevolvedVaal–Orangedrainagesystem.Thelegacy
of the latter stages of this westward transport is recorded in a number of erosional levels and terrace deposits within the
Lower Vaal Valley. Some of these coincide with ancient landscapes dating back to pre-Karoo times (>300 Ma) that have
been exhumed in post-Gondwana times. In addition, the erosion of older sedimentary sequences, in particular those on
the Limpopo–Vaal River watershed around Lichtenburg–Ventersdorp, believed to be of Permo-Carboniferous age (De Wit
2015,2016inpress)wouldhaveaddedtothepost-Gondwanaerosioncycle.Thequantityofdiamondsthatwouldhavebeen
derived from the Archaean Witwatersrand conglomerates cropping out in the upper Vaal River drainage is not known.
4.2 Summary of the drainage history of the lowerVaal–Orange basin
TheOrangeRiver,togetherwithitsmajortributarytheVaalRiver,isthelargestwestward-flowingdrainagesysteminsouthern
Africa(Fig.2).Althoughlesscompetenttoday,thegeomorphicsettingoftheVaalRiversuggeststhatthisdrainageshouldbe
considered the axial or main trunk stream in this large basin. Nonetheless, the Vaal–Orange drainage is the principal fluvial
conduit (or conveyor) transporting sediment from the interior of southern Africa (source) to the Atlantic Ocean (sink).

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Figure 2.
Main alluvial deposits in relation to the producing kimberlite mines (after De Wit 1996).
Moreover, it has long been recognised that the current Vaal–Orange fluvial system represents a superimposed drainage
network, where an older, mature pattern has been branded into the landscape through rejuvenation by epeirogenic uplift
(inter alia, Du Toit 1910; Maske 1957; Wellington 1958; Partridge and Brink 1967; Helgren 1979; Van Wyk and Pienaar 1986;
Partridge and Maud 1987, 2000; De Wit 1993; De Wit et al. 2000; Ward and Bluck 1997; Partridge 1998). In addition to
superimposition that generally cuts across bedrock strike, the Vaal-Orange system has exhumed — in the Kimberley to
Prieska reach, at least — an ancient, pre-Karoo (>300 Ma old) drainage network that itself was glacially sculptured by the
Dwyka ice in the Late Carboniferous (inter alia, Du Toit 1910; Wellington 1958; Helgren 1979; Visser and Loock 1988).
4.3 Diamond-bearing gravels on the Limpopo–Vaal River watershed
Diamonds were first found in the North West Province, almost on the Limpopo–Vaal rivers watershed, in 1926. These
diamond-bearing gravels of the Lichtenburg–Ventersdorp area are associated with sinuous ridges or ‘runs’, a term first used
by Du Toit (1951) to describe these narrow, elongated, and sometimes sinuous positive ridges that occur at an elevation of
some 1 500 m on a flat to very gently southward-sloping surface, comprised almost entirely of dolomites of the Malmani
SubgroupoftheTransvaalSupergroup(Fig.4).Theruns,referredtoasthe‘oldergravels’(DuToit1951),aremainlycomposed
of gravels and breccias, course sands, and minor clay units. The runs, close to Randfontein in the east, to midway between
Lichtenburg and Mahikeng (previously Mafikeng/Mafeking) in the west (Fig. 3), cover an area of approximately 150 km
(E–W)by40km(N–S).Inthewest,aroundLichtenburg,theyareorientatednortheast–southwest;inthecentralpartsnear
Ventersdorp, north–south; and close to Randfontein, northwest–southeast (Figs 3 and 4). Reworked or younger gravels
occur as terraces to the south along the Mooi River and to the southwest near Mahikeng as a palaeoriver channel (Fig. 3).

7. 7
Diamond DEPOSITS
Figure 3.
Main gravel ‘runs’ (black) in the Lichtenburg–Ventersdorp area. Younger reworked deposits in green. Carlisonia
Mine (CM), Pienaar’s Pothole (PP), Van Wyk’s Pothole (VWP), Tirisano Mine (TM) (De Wit 2016).
Diamond mining in the Lichtenburg area (known as the Northern Field), and around Ventersdorp (the Eastern Field)
started approximately in 1926. Diamonds in the Southern Field (Schweizer-Reneke, Wolmaransstad, and Bloemhof) were
discoveredearlier.Thetotalrecoveriesfromallthreefieldsupto1984was14.4Mct(millioncarats)(Marshall1987),most
of which came from the Northern Field (9.7 Mct), with the Eastern and Southern fields each contributing some 2.7 Mct
and 2.0 Mct, respectively.
Mostresearchershaveadvocatedadepositionaloriginforthegravelrunsbysurfacestreamsinpost-Karoo,andlikelyLate
Mesozoic and Cainozoic times (Harger 1928; Wellington 1929; Williams 1932; Du Toit 1935, 1951; Cooks 1968; Partridge
and Maud 1997; Stratten 1979; Marshall 1990). Stettler (1979), De Wit (1981), and Marshall and Norton (2009) suggested
that the runs were controlled by leached and/or fracture zones in the dolomites and that the gravels were deposited in a
karst system. De Wit et al. (1998) reported preliminary data from mantle zircons and indicator minerals in the runs that
suggest input from local, but as yet undiscovered, kimberlites. Most recently, it has been shown that these deposits are
related to the last deglaciation of the Dwyka glacial period, dating back to the Late Carboniferous (De Wit 2015, 2016 in
press).

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Figure 4.
Elevationmap(3Dandlookingnorth)basedonSTRMdataofthewatershedoftheLimpopo(tothenorth)andVaal
rivers (to the south) basins, underlain by the Palaeoproterozoic Malmani Dolomites of the Transvaal Supergroup.
Main gravel ‘runs’ (black) in the Lichtenburg–Ventersdorp area. Younger reworked deposits in green. Carlisonia
Mine (CM), Pienaar’s Pothole (PP), Van Wyks Pothole (VWP), Tirisano Mine (TM) .
(Google image as background).
4.4 Evolution of theVaal–Orange drainage
Withsuchanactiveandlong-livedhistorytotheVaal–Orangedrainage,anumberofviewsontheevolutionofthisimportant
fluvialsystemhavebeengeneratedsincethecriticalobservationsreportedbyDuToitin1910.Frommoreextensivefieldwork,
supplemented by heavy mineral analyses and terrain evaluation techniques, (De Wit 1993, 1999, followed by Partridge 1998
and De Wit et al. 2000) it was proposed that the Vaal–Orange system originated as two parallel drainages following the
breakup of West Gondwana (Fig. 5). By Mid-Cretaceous times, a larger southern Karoo River debouched off the current
Olifants River mouth in southern Namaqualand and a northern Kalahari River deposited offshore at the current Orange River
mouth.SubsequentcaptureoftheupperKarooRivernearPrieskabythelowerKalahariRiverintheEarlyPaleogenehasbeen
invoked to generate the current drainage pattern (Fig. 4; De Wit 1993, 1999).
In an updated version of the original paper, Ward and Bluck (1997) suggested that by the Late Cretaceous, the
Vaal–Orange system had networked into a major, mature, and largely meandering drainage basin that was feeding
into a major delta represented by the offshore Kudu area of the northern Orange basin. The Orange–Vaal system
evolved from a free-meandering, large drainage system, with a fine-grained (sand/silt) discharge in the Late

9. 9
Diamond DEPOSITS
Figure 5.
Summary of southwestern African drainages (mostly Vaal River) in post-Gondwana times (after De Wit 1993,
1999).
Cretaceous–Early Paleogene, to a superimposed, steeper, bedrock-confined, gravel-transporting channel system
since the Early Paleogene (Ward and Bluck 1997). This change in fluvial character reflected the asymmetrical
uplift of the subcontinent and the consequent downcutting and entrenchment of the Orange–Vaal drainage — a
process that was initiated by Late Cretaceous to Earliest Paleogene times, rather than the mid- to Late Cainozoic
(Partridge and Maud 1987, 2000; Partridge 1998). The major incision phase of the Lower Orange River had been
completed by approximately 17–19 Ma, which is the palaeontological date of the aggradational Arries Drift Gravel
Formation (Corvinus and Hendey 1976; Pickford 1998; Pickford et al. 1999).
Despite varying opinions on the subject, considerable erosion of the southern African hinterland occurred during
the Cretaceous following the breakup of West Gondwana, the products of which lie largely offshore in the Orange
basin (inter alia, Dingle et al. 1983; Partridge and Maud 1987, 2000; Brown et al. 1995; Aizawa et al. 2000). During
this period, the bulk of the kimberlitic intrusions were emplaced in southern Africa (De Wit 1996; Lynn et al. 1998).
Significantly, the widespread occurrence of crater fill facies in the Late Cretaceous to Earliest Paleogene volcanic pipes
in Namaqualand across to Gordonia implies reduced erosion rates for the western area during the Cainozoic (Scholtz
1985; Smith 1986; De Wit et al. 1992).
Continued downcutting through the Cainozoic in response to intermittent, asymmetric epeirogenic uplift, and influenced by
climaticchanges,aswellaseustaticmovementsinthedistalreaches,ensuredthedeepsuperimpositionoftheVaal–Orange
drainage (e.g. Partridge and Maud 1987, 2000). This long-lived superimposition of the Vaal–Orange system is recorded by
the terrace remnants preserved progressively down from higher (older) to lower (younger) levels (Fig. 6 and Table 3) within
the drainage basin (Marshall 2004; De Wit et al. 2000), as follows:

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1. Late Cretaceous to possibly Early Paleogene (mostly >75 m above current river level): Nooitgedacht and Droogeveldt
gravels in the Lower Vaal basin, Terraces A1 and A2 along the Middle Orange, Mahura Muthla on the Ghaap Plateau
(Partridge 1990; De Wit et al. 2009).
2. Miocene (approximately 60 m above current river level): Holpan Terrace and equivalents of the Lower Vaal basin, Terrace
B along the Middle Orange, Renosterkop upper potholes and Daberas potholes in the Augrabies area, Arries Drift Gravel
Formation (incorporating the pre-Proto and Proto-Orange River gravels) along the Lower Orange reach, and Bosluis Pan
and Galputs in the Koa Valley tributary to the Lower Orange.
3.Pliocene(approximately20–40mabovecurrentriverlevel):ProkschKoppieandWedburgterracesoftheLowerVaalBasin,
Terrace C along the Middle Orange, Meso gravels of Renosterkop and Lower Orange Valley (sensu Fowler 1976), and +50
m and +30 m marine packages along the Atlantic coast.
4. Late Pliocene to Holocene (<20 m above current river level): Riet Put and Riverton Formations in the Lower Vaal basin and
along the Middle Orange, fine-grained terraces flanking the Lower Orange River, some of which have been attributed to
large-scale flooding by the river in the Holocene (Zawada et al. 1996).
4.5 Brief history of South African diamond occurrences
From 1867, when the first diamond was found in South Africa on the banks of the Orange River near Hopetown (Table 4;
Williams 1905, Wagner 1914), to 1926 ,and again from the late 1950s to early 1980s, a steady discovery of diamond deposits
occurred, both primary and secondary.
Although some diamonds were picked up along the Vaal and Orange rivers in the late 1800s, it was the 21.25 carat
diamond (Eureka) in 1867 and the 83.5 carat diamond (Star of South Africa) in 1869 that sparked a worldwide interest in
diamond exploitation in South Africa. Active digging operations started near Hopetown and Canteen Kopje at Barkly West
(Klipdrift)between1868and1870.‘Gravels’containinghighconcentrationsofdiamondswerealsofoundnearJagersfontein,
Koffiefontein, and Kimberley. These ‘dry diggings’ were later recognised as weathered zones of primary kimberlite pipes,
which led to the development of the Jagersfontein, Koffiefontein, Du Toitspan, Bultfontein, De Beers, and Kimberley primary
diamond mines in the 1870s. Later, in 1891, the Wesselton pipe was discovered.
Continued digging activities around Barkly West during the 1880s exhausted many of the richer alluvial deposits and the
prospectorsmovedtothe‘dry’diggings,uptoWarrenton,Christiana,andBloemhof,andfurtherintotheNorthWestProvince.
DiamondsweresubsequentlyfoundnearPretoria,whichultimatelyledtothediscoveryofthePremierMinein1903.Thiswas
followed by the discovery of the Voorspoed Mine in 1906 in the Free State Province.
In 1912, the discovery of diamonds near Schweizer-Reneke led to the exploitation of the southwestern Transvaal alluvial
fields.Inthesameyear,intheKimberleyarea,payablehigh-levelgravelswerediscoveredonthefarmDroogeveldt(292)and
many diggers subsequently moved to the Vaal–Orange confluence.
Figure 6.
Schematic section
through the gravel
terraces of the Vaal
River basin (after
Marshall 2004).

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Diamond DEPOSITS
1866–67
1868
1869
1870
1870
1871
1880
1880s
1891
1896
1903
1906
1909
1912
1912
1912
1918-19
1926
1926
1926
1928
1958
1960
1962
1963
1972
1980
1986
2008
2015
Secondary occurrences
Orange River 21.25 ct (Eureka)
Few diamonds near Barkly West
Orange River (below Orange–Vaal confluence 83.5 ct (Star of SA)
Vaal River diggings near Barkly West
Diggers start moving to Warrenton, Christiana, and Bloemhof
Found by geologist HS Harger, bought by De Beers in 1912, opened and closed 1912
Small diamonds at Alexander Bay (Martin)
Schweizer-Reneke (Mooifontein, London)
Droogeveld (Barkly West)
Diggers move to Orange–Vaal junction (Douglas, Hopetown, Prieska)
Lichtenburg diamond fields
Namaqualand (Kleinzee, Port Nolloth)
Orange River Mouth (Alexander Bay)
Mining Area No. 1 (Sperrgebiet Namibia)
Buffels River deposits (Namaqualand)
Nearshore (surf) (Sammy Collins)
Lower Orange River deposits (Octha)
Offshore shelf (90–200 m depth) (Atlantic Ocean)
Re-opening of the mine
Re-opening of the mine
Kimberlites
Jagersfontein Mine (Free State Province)
Du Toitspan Mine (Northern Cape Province)
Bultfontein, De Beers, and Kimberley mines
(Northern Cape Province)
Koffiefontein (Free State Province)
Wesselton Mine (Northern Cape Province)
Lace Mine (Free State Province
Premier Mine (Gauteng Province)
Voorspoed Mine (Free State Province)
Postmasburg Mine (Northern Cape Province
Finsch Mine (Northern Cape Province)
Venetia Mine (Limpopo Province)
The Oaks Mine (Limpopo Province)
Voorspoed Mine (Free State Province)
Lace Mine (Free State Province)
Major ‘alluvial’ fields were discovered in 1926 at Lichtenburg, in Namaqualand, and close to the Orange River mouth. This
resulted in a major increase in alluvial production in South Africa from 1926 to 1930.
However, production declined rapidly after 1930, partly owing to the world depression, but also to legislation preventing
further exploration in Namaqualand. Changes to the legislation in 1958 led to the discovery and subsequent exploitation
of alluvial diamonds along the Buffels River. Continued exploration in Namaqualand resulted in the discovery of major
fluvial deposits along the Orange River from the late 1960s to the early 1970s (Wilson 1972a, 1972b). Furthermore, marine
exploration opened up the continental shelf in 1972.
Table 1. Discovery history of primary and secondary diamond deposits in South Africa

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4.6 Interior geomorphic trapsites
AsmuchoftheVaal–OrangecatchmentisunderlainbytheKaapvaalcraton,diamondiferouskimberlitesarebutonecasualty
oftheprolongederosionofthesouthernAfricanhinterland.Theseinterioralluvialdiamondfieldshaveyieldedapproximately
20 million carat since approximately 1870 (modified from De Wit 1996). Walker and Gurney (1985) estimated — based
on Hawthorne’s kimberlite model (Fig. 30) and associated erosion levels of primary sources in southern Africa — that at
least 3 billion ct would have been liberated in post-Gondwana times. Recently, this level of erosion has been challenged
and reduced (Hanson et al. 2006). Nevertheless, the inland alluvials account for only 0.6% of the diamonds that have been
removed by erosion of the known kimberlite pipes on the Kaapvaal craton.
There are almost no alluvial diamond deposits on Karoo bedrock. Exceptions are the deposits near Aliwal North between
DouglasandPrieskaalongtheMiddleOrangeRiver(MOR),andtheBrandvleiandSetadepositsnearMessina,whichareboth
smallandextremelylowproducers.ThebulkofthealluvialdiamondsoccuralongthenorthernrimoftheKaroobasin.Thisis
related to the asymmetrical uplift of the southern African continent (De Wit 1993, 1996). Additionally, the absence of alluvial
diamonds proximal to the main primary producers (Fig. 2) illustrates the fact that the horizontally bedded finer sediments
of the Karoo are almost incapable of trapping diamonds, except where dolerite dykes and sills produce sufficient riffling, and
where breakdown of the Dwyka produce sufficient boulder and oversize material for some concentration to occur. Where
rivers leave the Karoo base and encounter the pre-Karoo surface, especially where this is composed of resistant Ventersdorp
Supergrouprocks,significantplacerdevelopmentoccurs.Thereasonsaretwo-fold.Firstly,thecompetenceandirregularityof
the pre-Karoo base is sufficient to trap coarse debris that, in turn, acts as diamond traps. Secondly, weathering of the base of
the Karoo tillites of the Dwyka Group and the exfoliation of the Ventersdorp lava produce the pebbles, cobbles, and boulders
that comprise the coarse detritus. This could explain why it has been suggested often that the diamonds could have derived
from the Dwyka tillites (Maree 1987; Moore and Moore 2004).
Many diamonds larger than 100 ct have been reported from the Waldeck’s Gravel Splay, Nooitgedacht and Droogeveldt
deposits, close to the Kimberley mines. The same applies to the area south of Windsorton (Leicester Mine). Therefore, the
presence of large diamonds can, in certain circumstances, be related to the proximity of a primary source. As mentioned
earlier, another interesting observation is that the diamond mineralisation of river terraces seems to improve with increased
age (Van Wyk and Pienaar 1986; De Meillon and Bristow undated; De Wit 1996; Jacob et al. 1999)
Finally, the gravel splay deposits have been identified as major geomorphic features, often structurally controlled, which
are extremely effective diamond trappers. The following main gravel splays were identified: Holpan–Klipdam (130 000 ct)
(R. Cooke, pers. comm.) and Waldeck’s Gravel Splay (530 000 ct) (De Wit 1996) on the Vaal River, the Brakfontein deposits
on the Middle Orange River, and the Skutsekama deposit on the Riet River.
The deposits at Holpan (161) and Klipdam (157) (Stop 10) have been subdivided into three gravel types (Partridge and Brink
1967) and appear to have a stratigraphy similar to those that occur in the Bloemhof area.
The channels (or ‘sluits’) that occur on Droogeveldt (292) are, like Nooitgedacht (66), at least 85 m above the level of the
present Vaal River. The Droogeveldt field has been described in detail by Spaggiari (1993) and Spaggiari et al. (1999). This
deposit,unlikeNooitgedacht,comprisesproperfluvialchannels,whichhaveproducedsome490000ct.Thelargestdiamond
found here was 308¼ ct, with about 18 stones >100 ct.
Thegravelsplaydeposits,WindsortonandWaldecks(VaalRiver)andSkutsekama(RietRiver),areyoungerthanthesediments
on Nooitgedacht (66) and Droogeveldt (292), and occur only between 5 and 20 m above the present river level. These are

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Diamond DEPOSITS
spreadoverseveralfarmsanddisplayacoarsetofinegradationfromtheproximaltothedistalendofthesplay.Itisinteresting
to note that, in general, the diamond sizes and grades follow this fining trend (Mattheys 1990). Both the Skutsekama and
Waldecks deposits have produced a total of 48 diamonds over 100 ct in size between 1872 and 1930. The majority of these
came from the proximal reaches of this gravel splay.
4.7 Estimates of diamond production from the secondary deposits
The North West Province has produced the bulk of the alluvial diamonds. Between 1904 and 1984, the production was
Lichtenburg 9 700.000 ct, Ventersdorp–Potchefstroom–Klerksdorp 2 600 000 ct, and Bloemhof–Schweizer-Reneke–
Wolmaransstad 2 700 000 ct (Marshall 1989, 1990, 1994; De Wit 1996).
The Kimberley area alluvials have produced between 1 500 000 and 2 000 000 ct, although this figure could be somewhat
higher.Depositsthathaveproducedbetween100000and1000000ctincludeDroogeveldt,theHolpan–Klipdam‘run’,and
Waldeck’s Gravel Splay (De Wit 1996, Lynn et al. 1998).
West of the escarpment, the Buffels River alluvials have produced a total of approximately 1 000 000 ct.
To date, the Lower Orange River has produced approximately 2 000 000 ct. The size, quality, and the value of the Lower
Orange River diamonds are superior compared with those from the Lichtenburg field, and compare favourably with those
from the Lower Vaal and Middle Orange reaches.
5. Stops
Monday 22 August 2016
WedepartfromtheORTamboInternationalAirport,Johannesburg(26°8.190’S;28°14.469’E),at10:00on22August.Wewill
be driving in a westerly direction across the Johannesburg–Pretoria area for approximately 210 km in the direction of Koster,
to the first stop at the Tirisano Diamond Mine, north of Ventersdorp. The estimated time of arrival at the mine is between
13:00 and 14:00.
Stop 1:Tirisano Diamond Mine (26’5.218’S; 26’47.121’E)
The Tirisano project, located in the North West Province of South Africa, is approximately 35 km due north of the town of
Ventersdorp,approximately200kmwestofJohannesburg.Untilrecently,themainNooitgedachtgravelrunhasbeenmined
onalargerthanartisanalscalebyseveralcompanies(Fig.7).Upto1984,threepropertiesalongthisrun,Nooitgedacht131IP,
Hartbeeslaagte146IP,andZwartrand145IPproduced36863ct.Fromtheearly1990supto2012,itproducedanadditional47
033 ct (company reports of Etruscan Resources Inc., Rockwell Diamonds Inc., and Transhex Group Ltd) when it was operated
by mid-tier companies (Figure 7).
Thedepositcomprisestworuns,themainorVetpanrun,andawestrun,whichhasbeenlesswelldefined.Thegravelshave
been subdivided into several units (Figs 8 and 9), the most important being the lower gravel package (LGP), followed by a
small pebbly clay package with sand lenses (PCP), and the upper gravel package (UGP) (Marshall and Norton 2009). In the
deeperpartsofthemaindepressionandbelowtheLGP,thereisabasalgravelpackagedominatedbyroundedclastsofwhite
to grey quartzites. The LGP is generally clast supported, with a reddish-brown clay matrix (Dcm lithofacies), but becomes
matrixsupportedandmoreclayrichintheupperpart,whereitisreferredtoasthetransitionzonepackage(TZP).According

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Figure 7.
Aerial view highlighting the structural control of the Tirisano deposit (Marshall and Norton 2009).
to Marshall and Norton (2009), the LGP contains red diamictite clasts that have been assigned to the Waterberg
Group. The intermediate PCP unit comprises clays (white to light yellow in colour) and pebble to small cobble
lenses. The UGP is generally coarse grained, poorly sorted and clast supported, and the matrix is yellow-brown
clay (Marshall and Norton 2009). Parts of the UGP are stratified, with large horizontal metre-scale and low-angle
gravel beds (Gm/Gms). The diamond grades of the LGP are approximately 1.2 cpht, whereas that of the UGP is 0.7
cpht (Marshall and Norton 2010). A large part of the gravels has been preserved in a depression at the intersection
of two major structures, and is overlain by sandy clay that extends beyond the confines of the sinkhole. The LGP is
confined to the deeper parts, whereas the UGP occurs on the western shoulder, spreading beyond the depression as
sheet gravels. The main components are locally derived chert and well-rounded quartzite derived from the Pretoria
Group sediments to the north.
The clasts in the LGP are generally well rounded, whereas those in the UGP are both rounded and angular, especially the
chert. The depositional processes of these gravels have been described as not typical fluvial–alluvial and during periods of
periodicsubsidence(Marshall and Norton 2009).
The average bulk-sample grades were 2.37 ct/100 m³, being the combination of the shallow UGP at 1.77 ct/100 m³ and the
deeper LGP at 2.85 ct/100 m³. The rough diamond price for the Etruscan parcels has continued to drop since October 2008,
with final sales figures at an average of USD520/ct for 2008. As a result, Etruscan considered it prudent to halt production
from Tirisano (Marshall and Norton 2010).
Overnight in Lichtenburg.

15. 15
Diamond DEPOSITS
Figure 9.
Schematic stratigraphic model for the Ventersdorp alluvial diamond deposits (Marshall and Norton 2009).
Figure 8.
General stratigraphy, as seen at the Tirisano Mine (pit 6) (Marshall and Norton 2009).

16. IGC 2016
16
Tuesday 23 August 2016
Thedaywillbespentvisitingseveralsitesofthemostlymined-outareasofthediamondfieldnorthofLichtenburg,between
the famous Welverdiend Mine and Bakerville, as originally mapped by Du Toit (1951).
Figure 10. Main digging areas north of Lichtenburg (Du Toit 1951).
Stop 2: Manana Run (26’5.185’S; 26’12.865’E)
Between the Bakerville (30.8 km) and Twee Buffels (28.9 km) gravel runs are four shorter runs, all orientated almost north–
south.Theseare,fromwesttoeast,theLichtenburg(3km),Manana(7km),Witstinkhoutboom(4km),andSchilpadverdriet
(3.5 km) runs. Together, these have produced nearly 270 000 ct, with most of the diamonds (230 000 ct) coming from the
Manana run. The presence of Rooihoogte Conglomerate and Pretoria Group quartzite clasts in the gravels suggest that the
source area was to the northeast. This is supported by the distribution of andalusite minerals in the soils in the Lichtenburg
district,derivedfromhornfelslocatednortheastofZeerustandSwartruggens,whichdecreaseinconcentrateandincrease in
roundness in a southerly direction (Mayer 1985).
TheMananarunis7kmlongandisorientatedtowardsthesouth-southeast(Fig.11).Thediggingsstartinalargedepression
westoftheroadfromLichtenburgtoWelverdiend.Thereisnosignorrecordthatthesegravelscontinuetothewest.Therun
then swings to the south-southeast and attains a width of between 100 and 150 m over most of its length. It thins in the
south, where it terminates on dolomite just before the Karoo outlier, east of Lichtenburg (Fig. 11). Drill holes into this Karoo-
filled valley intersected Dwyka Group sediments overlying Ventersdorp Supergroup volcanic rocks (Lynn 2014).
Thegraveliscomposedmainlyofsubangularbluechert,someooliticandroundedpebblesofredquartzite,greentogreyand
black chert, and vein quartz. No agates were found. The quartzites derived mainly from the Pretoria Group to the northeast.
Texturally, the gravel is a massive, poorly sorted diamictite (Dmm and Dcm), which is clast and matrix supported, with a
matrix of maroon-coloured clay. It is underlain and grades into chert breccia (BBm) and blocks of weathered chert. Some of
the excavations are up to 15 m deep.

17. 17
Diamond DEPOSITS
Figure 11.
Aerial view of the Manana gravel run meandering across the surface, looking north.
Stop 3: Carlisonia Mine onWelverdiend (25’58.612’S; 26’11.363’E)
Aturn-offtotheeastisafurther10.7kmnorthward,adjacenttosomemajortailingdumpsnexttotheroad,directlyopposite
the Carlisonia Township (Fig. 12). This complicated structure stretches over several hundred metres in all directions. A deep
hole,approximately50mindiameter,hasbeenminedtomorethan30mdeepbyWelverdiendDiamondsLtdbetween1927
and 1933, duringwhich time some 1.6 million ct were extracted. The areawas generally referred to as theJewel Box. Agates
are abundant and some spectacular dolomite pinnacles, or dolines, rise above the excavations on the eastern side of the
sinkhole. The material enveloping these buttresses consists of manganiferous wad, which forms by the progressive solution
of these dolomites, and manganiferous gravel or chert rubble with occasional worn pebbles. In the centre of the Carlisonia
Mine were patches and irregular bands of maroon clay, often closely associated with the gravel, and, in places, these bands
were tilted vertically. These are generally rich in unabraded agates (red carnelians and yellow chalcedonies).
Figure 12. Aerial view of the Carlisonia Mine on Welverdiend looking toward the southwest. Tailings dumps
surround the main digging area.

18. IGC 2016
18
Weathered friable feldspathic sandstone blocks, in places bioturbated and containing highly polished and rounded pebbles
of chert and quartzite, together with small slabs of white, bleached, shaly strata strongly resemble upper Karoo Supergroup
(Triassic)beds.Thelowergravels,nowmainlyminedout,wererichinagatesandsomejasper,gradingupwardintotheupper
gravels, which were coarser and generally poor in agates. Karoo fossil wood has been reported from Welverdiend (Du Toit,
1951).
The diamonds from the Welverdiend area, which produced some 1.6 million ct since 1926, were only valued at some R3.63
per carat (De Wit 2016). This is mainly because most of those diamonds were produced and sold in the late 1920s. It is in-
teresting to note that the diamonds from Welverdiend are different in terms of value to those derived, for instance, from the
Vlakplaats run further to the west.
Stop 4: Pienaar’s Pothole on the farm Ruigtelaagte (25’58.165’S; 26’8.957’E)
This is the deepest known large ‘pothole’, situated on the south side of a gentle depression, approximately 400 m across. It
is situated south of the east–west Welverdiend–Grasfontein run (Fig. 13). It was mined extensively from 1927 to 1933 and
has produced over 0.5 million ct of diamonds. It has been mined to at least 120 m and the bottom has never been reached,
as strong groundwater through the dolomites prevented further excavation (Du Toit 1951). Du Toit mainly derived his basic
stratigraphy from this location (Fig. 14 and Table 2).
Figure 14.
Section across the famous sinkhole (Pienaar’s Pothole) on Ruigtelaagte (after Du Toit 1951).
1 – white sandy clay
1b – yellowish and pinkish sandstone
1c – white to pinkish pipe-clay
1d – black clay
2 – yellowish to red gravel
3 – stratum of maroon clay
4 – lower gravel
5 – upper red gravel
6 – upper gravel
7 – red Hutton ‘Kalahari’ sand

19. 19
Diamond DEPOSITS
Figure 13.
Pienaar’s Pothole from the air looking toward the northwest. Note the additional holes (S1 and S2) dug northeast
of the pothole that were found later by using geophysical methods (Stettler 1979).
Table 2. Summary of the various lithologies within Pienaar’s Pothole, as shown in Figure 13
Lithologies
Red Hutton sands
Upper gravel
Upper red clay
Lower gravel
Maroon clay in places
Lowest yellow to red gravel
White zone
Unit
7
6
5
4
3
2
1
Comments
Can be up to 10 m thick.
Overlapped the clay and rested on dolomite in the
NNE, on the white zone in the E and SE, and on the
lower gravel in the ESE.
Covered the entire sinkhole, 2 to 3 m thick, but
thickened to 25 m in the SW.
Productive gravel 7 to 10 m thick. Particularly rich in
diamonds in the lower part.
Several metres thick, carried agates.
White sandy material with conglomerate lenses. No
agates or diamonds.
Agates are scarce, with angular chert dominating,
with some quartzite, and vein quartz. Diamonds
occur in low grades.
Poorly bedded, with a fossil tree trunk found
within it.
Well-bedded with small- to medium-size pebbles
of green chert, quartzites, and hornfels, abundant
grey, yellow, and red agates.
Unidentifiable plant material has been found.

20. IGC 2016
20
Stop 5: National Monument at Elandsputte cattle dip (25°58.331’S; 26°05.900’E)
It is the year 1924. A very difficult year for the Voorendyks of Elandsputte. John Voorendyk, postmaster of Lichtenburg,
has been dejected for a long time. He cannot get a buyer for his farm, not even for the low-low price of 7/6 (shilling/
pence) a morgen. And his cattle are dying of an unknown illness. On advice of his son Koosie, they start digging a
cattle dip. The dip hole was finished and they are now busy digging the last hole for the kraal poles. Then, suddenly,
the worker’s eye catches a glitter in the gravel. He picks up a small stone and shows it to Koosie. “Dad! Look! A
diamond!!” Not quite sure what to believe, but remembering the diamonds sporadically found in recent years in the
district, they took the diamond to the local science teacher, Mr Bosman, to put the stone through an acid test. It was
December 1924 ... A beautiful stone of 3 carat! Not flawless or blue-white, but, nevertheless, a real diamond!
The remnant of the original cattle dip has been declared a national monument and, although somewhat overgrown, can be
found near the homestead on Elandsputte, south and several hundred metres along the Klipkuil road.
Stop 6: Malan’s Pothole on the farm Grasfontein (25°59.743’S; 26°3.414’E)
Malan’s pothole is one example of a narrow pothole with steep dolomite wall rock. This pothole is located immediately
southofthedirtroad,some4kmwestofBakerville,onthefarmGrasfontein.ThepotholeisdirectlysouthoftheGrasfontein
Township. It occurs as a narrow, almost east–west-orientated ‘yama’, which is a steep-sided karst feature that often merges
into caves at depth. Although typical yamas are vertical shaft features, Malan’s and King’s potholes are more fissure like, and
these may well represent the remnants of kimberlite dykes that have been completely decomposed and gradually replaced
by gravel infill. This normally happens to ultrabasic rocks, especially in a cavernous and karstified host with large amounts of
water flushing through it.
This farm had produced more than 2 million ct by 1945 and 2.5 million ct by the 1960s. North of this hole, the gravels form
sheet-like deposits, which are mainly composed of chert fragments and some rounded pebbles (the remnant material of the
weathering of the dolomites). The famous King’s Pothole (Stop 8) occurs almost 1.5 km north of Malan’s Pothole, also on the
farm Grasfontein.
Stop 7:VanWyk’s Pothole or MSG, Grasfontein (26°0.071’S; 26°2.807’E)
When Van Wyk’s pothole was mined in the late 1920s, the bottom had not been reached at 40 m depth (Du Toit 1951).
Reputedly, on one occasion, 2 100 ct of diamonds were recovered within 24 hours. The upper pale gravel and the lower
red gravel in this part of the digging area are well developed, but this site is underlain by whitish gravel, almost cylindrical
in shape (Fig. 15), which descends into the weathered dolomite (Du Toit, 1951). This gravel has a greyish clay matrix and
contains green chert clasts, diamonds, and agates, with boulder-size ‘polished’ chert found lower down.
A detailed geophysical survey (ground gravity) identified this as a major gravity low (De Wit 1981), and more recent
excavations on this low have indicated high diamond-grade material at depth, with several thousand carat of diamonds
having been recovered. It also contained a high abundance of unabraded kimberlitic garnet and spinel grains. In addition,
the diamonds contained a high percentage of boart and fragile stones, all suggesting a proximal source. Finally, two of the
diamondscontainedclinopyroxeneinclusions(Fig.17),whichweredatedandindicatedthatthekimberlitesfromwhichthey
were derived were Cambrian in age (500 Ma) (De Wit 2015, 2016 in press). These ages coincide with a pulse of diamond-
bearing kimberlites of that age in southern Africa, e.g. Venetia, the Oaks, River Ranch, and Murowa (Jelsma et al. 2009).

21. 21
Diamond DEPOSITS
Figure 15.
Du Toit’s (1951) section of
Van Wyk’s (MSG) Pothole.
1 – weathered dolomite
2 – whitish gravel
3 – chert boulders
4 – lower red gravel
5 – upper pale gravel
Figure 16.
Van Wyk’s Pothole (MSG) excavated in recent times, looking southward. Note the almost north–south-
orientated structure.

22. IGC 2016
22
Figure 17.
Diamonds with
clinopyroxene inclusion,
analysed by Ar/Ar
dating technique.
Stop 8: King’s Pothole, Grasfontein (25°59.084’S; 26°3.330’E)
On the sheet-like gravel deposits on the northern side of Grasfontein is a similar gully or ‘fissure’, this time trending north–
south in the slightly dipping dolomites. It is deep, but not more than 10 m wide on top. Deeper down, the rocky walls
are only approximately 3 m wide. This hole was mined to a depth of approximately 50 m (Du Toit 1951), below which
stronggroundwaterpreventedthediggersdeepeningthepotholefurther.Indepth,theinfillingmaterialwasyellow-greyish
calcareous clay, carrying pale-green chert pebbles, agate, and white quartzite schist, and kimberlitic garnets. In addition,
analysis of this clay suggests it has an ultramafic parent.
Overnight in Lichtenburg.
Wednesday 24 August 2016
Stop 9: London Run, Schweizer-Reneke (27°20.380’S; 25°25.662’E)
A detailed study of the palaeodrainage of the area north of the Vaal River (Fig. 18) suggests little deviation from the
present pattern (Marshall 1986). It has been suggested that the main Vaal channel migrated southeastward with time. The
reconstruction of the palaeodrainage shows how gravel lithologies could have been transported from eastern Botswana to
Bloemhof via the London–Klipbankfontein run.
The basal rocks are lavas of the Ventersdorp Supergroup and isolated patches of Dwyka tillite. The London run is buried
beneath 1 to 15 m of calcrete and consists of pebble- to boulder-size Ventersdorp lava and pebble-size quartzite, agate, and
vein quartz (Marshall and Norton 2012). The gravel varies in thickness between 0.5 and 4.0 m, and has a sandy matrix. In
contrast, the Rooikoppie gravels are developed above and along the flanks of the channel. Pebble- to cobble-size material
consists almost entirely of resistant siliceous material. These gravels are generally shallow (0–2 m), unconsolidated, and
averagebetween0.3and0.5minthickness(Fig.19).NamakwaDiamondsLtdoperatesthemineandhasgenerouslyallowed
access to the site.

23. 23
Diamond DEPOSITS
Figure 18.
Palaeodrainage
reconstruction based on
LANDSAT imagery
(Marshall, 1986).
Stop 10: Klipdam,Windsorton (28°19.478’S; 24°38.865’E)
The discovery of alluvial diamonds along the banks of the Vaal River near Barkly West in 1868 led to the great South African
diamond rush and the development of the diamond industry as it is known today (De Wit 1996). Diggers from Barkly West
subsequently uncovered the ‘dry-diggings’ in the adjacent Kimberley area, leading to the development of the Kimberley
diamond mines. The Vaal River, along with the section of river between the towns of Windsorton and Barkly West, the
Longlands–Gong-Gong gravel splay downstream of Barkly West, and the Riverview splay adjacent to Windsorton, became
famous for the mining of alluvial diamonds. The Holpan–Klipdam properties are located within this area, between Barkly
WestandWindsorton.BothHolpanandKlipdamwereminedfromtheearliestdaysandarewellknownforyieldingdiamonds
as large as 412.5 and 220 carat (Beet 1931).
Figure 19.
Historical production of the
London run and a typical cross
section based on drill hole results
(Namakwa Diamonds Ltd – London
112HO, Technical statement 2008).

24. IGC 2016
24
Because of the regular yield of large diamonds, Holpan and Klipdam have been the site of digging and mining of surface
deflation Rooikoppie deposits since the discovery of the Barkly West diamond fields. Digging operations during the 1880s
and early 1890s exhausted many of the richer Rooikoppie deposits near Barkly West, leading prospectors to move farther
upstream to Warrenton, Christiana, and Bloemhof, and into the then province of Transvaal.
With the strong decline of the South African rand against the US dollar during the 1990s, and the abundant availability
of cheap electrical power, alluvial diamond mining became an attractive option again. Activity along these large drainage
systemsandsmall-scaleminingordiggingoperationsonceagainbecamecommonalongtheLowerVaalRiver,withthemain
areas of interest being concentrated near Windsorton and Barkly West. The stratigraphy of the Lower Vaal River is relatively
simple. The bedrock consists of lavas of the Ventersdorp Supergroup (± 2.7 Ba) overlain by Permo-Carboniferous Dwyka
tillitesandKarooshales(280–250Ma).TheCainozoicfluvialdepositsthathavebeenminedareunderlainbytheseformations
(Fig.6andTable3).TheunconformitybelowtheKaroorockshasbeenshapedbyglacialandfluvioglacialprocessesthatwere
active during the Carboniferous. This, now partially exhumed, old landscape has been exploited by the Upper Mesozoic and
Cainozoic network of fluvial channels of the palaeo-Vaal River, and deposited gravels, sands, and silts in numerous cycles,
ranging from the late Cretaceous to the Holocene (Partridge and Maud 1987).
Table 3. Simplified stratigraphy of the Cainozoic alluvial deposits along the Lower Vaal River and the
Middle Orange River (Modified after SACS 1980; DeWit et al. 2000)
MESOZOIC–
CAINOZOIC
DEPOSITS
Upper Pleistocene
Middle Pleistocene
Pliocene
Miocene
Upper Cretaceous
LowerVaal River
A3 Gravels (Riverton alluvial gravels)
A2 Gravels (Rietputs alluvial gravels)
Intermediate Gravels (Proksch Koppie and Wedburg units)
CALCRETISATION
A1 Gravels (Holpan sequence)
A0 Gravels (Nooitgedacht deposits)
MOR
D
C
B
A
Partridge and Brink (1967) and Helgren (1979) recognised several levels of terrace development above the present Vaal River
and subdivided the alluvial deposits of the Lower Vaal Basin into ‘Older’ (Nooitgedacht, Holpan, Proksch Koppie, and Wed-
burg)terracedepositsand‘Younger’(RietPutandRivertonformations)gravelsonthebasisoflithologicalandtopographical
observations (Fig. 20).
TheWedburgterraceformsamorphostratigraphicmarkerthroughoutthelowerVaalRiverBasin(Fig.5).AtWindsorton,this
terrace occurs on both sides of the Vaal River at +22 to +24 m above the river. Between Windsorton and Barkly West, the
Wedburg terrace is irregularly preserved on both sides of the river. The Riet Put and Riverton formations or ‘Younger Gravels’
at Windsorton are part of a +12 to +14 m terrace. Younger Riverton Formation (IV and V) are located on lower +8 to +9 m
and+4to+5mterraces,respectively.ThegravelsoftheRietPutFormationmostlylieburiedbeneaththeRivertondeposits
and are often thick, and record primary depositional structures, with significant facies variation (Fig. 6).
Geologically,thegravelsontheHolpanandKlipdampropertiesareMioceneinage(±25–5Ma)(MarshallandNorton2012)
andarelocatedontheHolpanterrace,some60mabovethepresentVaalRiver.Geologicalmappinganddrillingresultsindi-
catethatthisriversystemflowedinawidemeander-loopacrosstheKlipdamandHolpanpropertiesandhasincisedsome20
mintothebedrock.Thelocationofthechannelappearstobecontrolledbytwodominantglacialscours,oneinanENE–WSW
direction and another in a N–S orientation (Fig. 21). These scours (filled with Dwyka tillites and younger gravels) were likely
carved out along pre-existing fracture/joint patterns.

25. 25
Diamond DEPOSITS
Figure 20.
Location of
known, mapped
terraces between
Windsorton and
Barkly West
(redrawn after
Helgren 1979).
The two well-developed palaeochannel features (Fig. 15), containing extensive coarse gravel sequences, are capped by
calcretised sand and silt layers and a few coarser gravel lenses (Marshall and Norton 2012).
The gravels are frequently cemented by groundwater calcrete to form calcretised cobble and boulder deposits. The gravel deposit
appears to be massive and is generally poorly sorted boulder gravel (clasts sizes up to 45 cm in diameter). Clasts consist mainly
of Ventersdorp lava, with minor banded iron formation, chert, quartzite, and quartz, and the total sequence could be 1 to 8 m
thick, with the gravel varying from 1 to 6 m in thickness. The fluvial-alluvial gravels typically rest directly on the Ventersdorp lava
bedrock.
Most of the area is typically covered with derived or Rooikoppie gravels that may, or may not, be underlain by varying
thicknesses of fluvial-alluvial deposits and are typically found on Ventersdorp lavas.
Figure 21.
Bedrock
elevation map
of Klipdam and
Holpan (after
Marshall and
Norton 2012).

26. IGC 2016
26
These deposits represent derived gravel and consist mainly of well-rounded and polished siliceous pebbles and reddish
colouredsand.Theclasticmaterialisbelievedtooriginatefromthefluvial-alluvialgravelunits(Marshall2004),butalsofrom
weathered and deflated Dwyka tillites. So-called colluvial Rooikoppie materials are typically 10–20 cm thick and consist of
uncemented, granular to pebbly gravel, with resistant clasts, and composed mainly of quartz, quartzite, and agate, set in a
matrix of dark-red, fine to medium sand.
The clasts are all ‘resistates’, composed of chert, agate, jasper, quartzite, vein quartz, and rare diamond owing to the
decomposition and winnowing of the less resistant clastic and matrix material. Iron staining gives it a reddish colour, from
which the name Rooikoppie derives, meaning ‘Red Hill’. Historically, these gravels were mined throughout the region by
small-scale prospectors using unsophisticated mining and diamond recovery techniques.
The Rooikoppie gravel could form on a karstified surface of a hardpan calcrete that has formed on primary gravel. The top
of the calcrete is subjected to solution weathering, and an irregular surface forms where the resistant clasts concentrate on
the surface and infill the depressions on the karstified calcrete, also called makondos. This eluvial material will be richer in
diamonds than the underlying alluvial deposit.
Similar deposits have been identified on the farm Nooitgedacht 66 (De Wit 2004), located on the east bank of the Vaal
River, just upstream from Barkly West, some 25 km directly south of Klipdam–Holpan. The Nooitgedacht deposit was rich
and contained typical Kimberley diamonds derived from the kimberlites in a shallow and wide depression that formed a
tributary to the palaeo-Vaal River, adding further diamonds to the drainage basin (De Wit 2004). It was suggested that
these Nooitgedacht–Rooikoppie deposits existed in the Cretaceous and, consequently, the Nooitgedacht deposit has been
associated with the African erosion cycle (sensu Partridge and Maud 1987).
During the period February 2009 to April 2012, trial mining on Klipdam and Holpan mines resulted in a weighted average
recovered grade of 1.03 ct/100 m³. The trial produced 40 627.76 ct at a combined average of USD791/ct and a mean stone
size of 1.01 ct/st. Stones +2.5 ct/st make up more than 80% of the value of the Klipdam/Holpan diamonds, although they
represent little more than 10% of the population (Marshall and Norton 2012).
Overnight in Kimberley.
Thursday 25 August 2016
Drive from Kimberley to the operations along the Middle Orange River (±160 km) of Rockwell Diamonds Inc. that has
generously provided access to these unique deposits.
Stop 11:
Brakfontein, Remhoogte, Saxendrift, Wouterspan and others, Middle Orange River (29°19.308’S;
23°15.257’E)
The present Orange River between Douglas and Prieska is generally referred to as the Middle Orange River and displays
a palaeomeandering channel morphology, best developed in areas underlain by the Dwyka Group. The main deposit at
Brakfontein was extensively mined between 1926 and 1936 and again in the 1940s (Fig. 22). Palaeochannel depositional
packages of the Orange River are preserved at different elevations above the present Orange River bed. The ages of the
terraces young with decreasing elevation and, conversely, the probability of preservation decreases with increasing age and
elevation (Fig. 24).

27. 27
Diamond DEPOSITS
Figure 22. Historical diamond production from the Middle Orange River (redrawn from Tefler et al. 2006).
Figure 23. Location of alluvial
mines along the Middle
Orange River operated by
Rockwell Diamonds Inc.

28. IGC 2016
28
The MOR deposit comprises an extensive flat-lying alluvial sequence located on terraces developed on the banks of the
present Orange River, approximately 20–70 m above the river (Fig. 23). The bedrock is well exposed in the workings, and
shale and tillite of the Karoo-age Dwyka Group are common. The fluvial-alluvial gravels comprise a sequence of (basal)
gravels 2–4 m thick, overlain by generally less than 5 m of variably calcreted sands and silts, covered by a thin layer of soil
and scree. The cobble-sized clasts within the gravels consist mostly of lava and quartzite, with significant, variable amounts
of banded iron formation (BIF), and minor amounts of limestone, tillite, and agate. The matrix is sandy to gritty. As is usual
with the deposits of this type, the degree of calcretisation decreases downward, and is characterised by hardpan or laminar
calcreteatthesurfacetolooselycementedgravelsatdepth.Thegravels,whicharegenerallyknowntobediamondiferous,are
typically not well-sorted, and are typical of braid bars that migrate through sections of river channels in response to variable
water speed.
Figure 24.
Interpretation of the various palaeorivers that were flowing at different times in the MOR region. River 1 being
the oldest (courtesy of Rockwell Diamonds Inc.).
Remhoogte Project
Bothcolluvial–eluvialandfluvial–alluvialgravelunitsareknowntoexistontheRemhoogteProject(Fig.25).TheRooikoppie
gravel thickness varies, ranging from 0.4 m to +1.0 m. The thin Rooikoppie gravel is generally pebble to cobble sized in a
sandy matrix. The thicker Rooikoppie ranges from cobble to pebble sized and pebble to boulder sized. The gravel sampled
from the edge of the terrace has a sand to pebble matrix. A high percentage of pebble clasts, with an abundance of banded
iron formation and chert (both black and blue varieties) are observed within the matrix. Other minerals observed include
jasper, quartzite, Ventersdorp lava, quartz, agate, and a variety of fibrous crocidolite, locally known as “Tiger’s Eye” because
of its golden-brown to red-brown colours.

29. 29
Diamond DEPOSITS
Figure 25.
General cross
section through the
Remhoogte deposit
along the Middle
Orange River (courtesy
Rockwell Diamonds
Inc.).
The nature of makondo development varies throughout the property. Both deeper, well-developed makondos and shallow
makondosareobserved.Thegravelfilloftheshallowmakondosisgenerallyfinercomparedwiththatofthedeepermakondos,
which is coarser. The shapes of the clasts infilling the makondos typically range from rounded to subangular, with pebble-
sized clasts dominantly rounded. The makondo observed can be connected or disconnected and also form channel-type
features. The depths of the makondos generally vary from 0.2 to +1.2 m.
The fluvial-alluvial gravels have not yet been characterised.
Saxendrift Mine
The Saxendrift Mine comprises processing plants and in-field screens, responsible for de-sanding and scalping of material,
which is subsequently processed through 4 x 18 ft (1.21 x 5.48 m) pans, coupled to final-recovery flowsort X-Ray machines.
Figure 26. Treatment
plant consisting of
scrubbers and pan
plants (‘wet plant’),
operated by Rockwell
Diamonds along the
MOR at Saxendrift
(courtesy Rockwell
Diamonds Inc.).

30. IGC 2016
30
The Saxendrift property consists of a number of different terrace levels (Terraces A–D; Table 3). Each terrace has its own
distinctive characteristics, which have been defined by the varying influence of the Vaal River and the Upper Orange River.
ThegravelsoftheUpperTerraces(TerracesAandB[CretaceoustoMiocene])compriseboulder-gravel,overlainbyanupward-
fining alluvial sequence of upper gravels and sand lenses. The lower terraces (Terraces C and D) of the Middle Orange River
are typified by an up to 30% sand matrix, with a high proportion of zeolite-rich sand lenses and a high proportion of red
Drakensberg basalt clasts.
The Middle Orange River alluvial deposits have yielded many large diamonds over 100 ct/st and several over 200 ct/st.
Overnight in Douglas.
Figure 27.
Some of the large
diamonds that have
been recovered from
the MOR. The diamond
at the top right is 287 ct
and was recently found
by Rockwell Diamonds
Inc.
Friday 26 August 2016
Drive from Douglas to Barkly West.
Stop 12: Panoramic view of theVaal River, and exfoliatedVentersdorp lava (28°36.463’S; 24°36.852’E)
In many places, the morphology of the Lower Vaal Valley is controlled by the pre-Karoo palaeotopography that was further
shaped and moulded during the Dwyka glaciation. Many sections of this valley are, in fact, glacial in origin and the flow
direction of the present-day river coincides with the Permo–Carboniferous ice-flow direction, i.e. to the south-southwest.
Stop 13: Glacial pavements, Nooitgedacht (28°35.962’S; 24°36.707’E)
OnaprominentmeanderoftheVaalRiver,some24individualglacialpavementsoccuroverseveralacres.Thesiteisanational
monument and no specimens may be taken. Pre-Karoo surfaces, which have been stripped of their Palaeozoic cover, can be

31. 31
Diamond DEPOSITS
found almost continuously along the modern channel of the Vaal River. Similar features can be seen along the pre-Karoo
bedrockreachesoftheRiet,Harts,andMiddleOrangerivers.Therefore,thebulkofthemodernrivervalleysintheLowerVaal
River basin are exhumed, glacially modified pre-Karoo valleys, as was first noted by Du Toit (1910), and subsequently well
documented by Helgren (1979).
StriatedsurfacesarepreservedinareaswheretheDwykasedimentshaverecentlybeenremoved(Fig.28).Themostfamous,
perhaps, are the ones exposed on the farm Nooitgedacht. Not only can two ice-flow directions be observed, but the rapid
lateral sedimentary-facies changes are also striking. In addition, the glaciers have sculptured the bedrock extrusives of the
VentersdorpSupergroup.Striations,chattermarks,pluckededges,anddrumlinoidcomplexesareprominent.VisserandLoock
(1988) supplied the most up-to-date description of this area. Concentric fractures found on these pavements have been
referredtoasHertzianfractures(Master2012)andhavebeeninterpretedtohavebeenformedbylargeerraticbouldersinthe
tillites under pressure from the overburden Karoo. These have been used to estimate the thickness of the Karoo Supergroup
that existed in the area to be 5 860 m (Master 2012). This is much higher than the estimates provided by Hawthorne (1975)
of 1 900 m and by Hanson et al. (2006) of 1 350 m of erosion since the early Cretaceous.
Figure 28.
The Nooitgedacht
pavements, showing
not only the groves and
striations as a result of
the Permo–Carboniferous
glaciation but also the
petroglyphs made by
ancestors of the San and/or
Khoe people.
Rock art on glacial pavements
Rock art occurs on the glacial pavements at Nooitgedacht (declared a heritage site in 1936), in the form of engravings (also
called petroglyphs). They were produced by pecking out the outlines or silhouettes of animals or ‘geometric’ designs with a
pointedstone(thereisnoevidencethattheartistsusedmetaltools,norindeeddiamonds,asissometimessuggested).These
images were made by the ancestors of the San and/or Khoe people (the authorship of the geometric images in particular
is subject to current debate), probably during the past 1 500 years. The engravings include depictions of humans, eland,
rhinoceros,ostrich,giraffe,andanteater(Fig.28).Themoreabstractformscandepictbagsandaprons,aswellas‘geometric’
designs,suchasarecommonatothersitesintheregion,particularlyDriekopseiland.Onescenariosuggeststhatwhereassites
such as the nearby Wildebeest Kuil, with its profusion of engravings of animals and some human figures, is quintessentially
San/hunter-gatherer in character, sites such as Nooitgedacht and Driekopseiland, where geometric engravings occur in great
numbers, could belong to a separate Khoekhoe herder rock-art tradition. A different perspective does not discount this

32. IGC 2016
32
possibility,butquestionswhetherassigningvariabilityintermsofethnicorculturaldistinctionsinthefirstinstance,doesnot
overlook other factors, such as ritual. At Driekopseiland, it has been argued (Morris 2012) that the ‘geometric’ engravings,
bags, and aprons could have been made as part of girls’ coming-of-age rites, which, in terms of beliefs and ritual practice,
exhibitsimilaritiesacrossthespectrumofSanandKhoekhoecontexts.Thelandscapesetting(avalleynearwater)mightitself
have been ritually significant, whereas hilltop sites could perhaps be more strongly associated with rain-making rites.
Stop 14: Nooitgedacht diggings (time permitting) (28°35.852’S; 24°38.309’E)
Followingthediscoveryofdiamondsin1869–70,variousclaimsandcounterclaimsweremadetoownershipofthisterritory.
Nooitgedachtfeaturedearlyon,whenthepresidentsoftheFreeStateandTransvaalrepublicsmetherewiththeGriquaChief,
Waterboer,andhisagent,DavidArnot,on18August1870.TheGriquarepresentativeswithdrewindisputeandtheFreeState
proclaimed the territory theirs. The disagreements were settled eventually by the Keate Award (in favour of Waterboer, who
placed himself under British protection), and the proclamation of the Crown Colony of Griqualand West on 27 October 1871.
The gravel deposits associated with the Lower Vaal River basin have been subdivided into older and younger gravels on the
basisoflithologicalandtopographicalcharacteristics(summarisedrecentlyinDeWitetal.2000;Table2,Figs6and29).The
rudaceous deposits on Nooitgedacht and Droogeveldt are of the highest elevated and, therefore, assumed oldest (Helgren
1979). These oldest post-Gondwana deposits in the Lower Vaal basin are assigned a Late Cretaceous age, based on their
siliceous clast composition and weathered status (De Wit 1999; De Wit et al. 2000).
Figure 29.
Schematic cross section
of the Vaal Valley
showing the relative
positions of gravel
platforms and terraces.
The Nooitgedacht ‘gravels’, which produced almost 100 000 ct, are spread across a pre-Karoo platform of Ventersdorp lava,
approximately 85 m above the glacial pavements on the same farm. Typical ‘gravel’ exposures are between 10 and 20 cm
thick,butcanincreaseto100–200cminplaces.Theyconsistofuncemented,granulartopebbly,subroundedtosubgranular
resistant clasts, mainly composed of quartz, quartzites, and agates set in a matrix of dark-red, fine to medium-grained sand.
All the larger boulders are locally derived core stones of Ventersdorp basalts. The deposit is extremely extensive laterally and
follows the bedrock irregularities with even thickness. The ‘gravel’ unit is overlain by dark-red, fine-grained sand, which is
analogous to the Hutton sands that could have derived locally from weathering of the underlying volcanic bedrock. It has

33. 33
Diamond DEPOSITS
been suggested that this deposit is a chemically weathered residue of an earlier diamondiferous alluvial deposit that drained
as a tributary from the Kimberley pipes into the axial Vaal drainage (De Wit 1988, 2004; De Wit et al. 2000). The presence
of a highly abraded population of diamonds and well-rounded exotic clasts suggests that this was mixed with sediments
of palaeo-Vaal River and Dwyka tillites, respectively. This deposit has produced one of the largest diamonds (the Venter
diamond, 511 ct) in the history of South African alluvial mining.
Exposures of these sediments are best illustrated at Koevoet Koppie and in the latest Dwyka diamonds mining faces. Large
core stones form the base of this deposit. Extremely few foreign pebbles are present here and manganiferous nodules are
the main component in the heavy mineral fraction. Kimberlitic heavy minerals (garnet and ilmenite) can be found in the
concentrate.
Stop 15: Canteen Kopje, BarkleyWest (28°32.504’S; 24°31.878’E)
Canteen Kopje, a national monument of historical value, is situated 1.3 km SE of Barkly West on the north bank of the Vaal
River. One of the hills near Canteen Kopje is said to be the site of the first actual diamond diggings on the diamond fields of
South Africa, which precipitated the rush of fortune-seekers to these parts in 1870. Diamonds were discovered there in 1869
anditbecamethe firstalluvialdiamonddiggingsinSouthAfrica(DeWit2008). AnAmerican,JeromeBabe,describedthese
events in 1872. The digger settlements that mushroomed along the river and at the ‘dry diggings’ that became Kimberley,
wrought changes in the local social and political landscape, with the new-found mineral wealth, and ensuing system of
labour migrancy transforming South Africa’s economy. It spurred the pace of conquest and colonisation.
Diamond digging, by way of shafts and tunnels radiating below the surface, continued intermittently at Canteen Kopje in
the years leading up to 1948, when the site was proclaimed a national monument. The sediments occur in a structurally
controlledandglaciallymodifieddepressionwithintheandesiticlavasoftheArchaeanVentersdorpSupergroup(Fig.30).The
fluvial gravels were deposited and mixed with the colluvium in the downstream end of a palaeoloop of the Vaal River as a
splay deposit, where the channel abruptly widens as it exits this narrow palaeoloop.
Figure 30.
Digital terrane map of the Barkly
West area. The positive feature
attached to the northwest side
of Canteen Koppie and inside the
circle is the main terrace deposit.
The arrows are aligned along the
major structural trends
(De Wit 2008).

34. IGC 2016
34
The gravel accumulation has been described as the 12 m to 16 m terrace package linked to the Younger Gravels of the Vaal
basin,andcorrelatedwiththePleistoceneRietPutFormation.Therearetwomaingravelandonesandfacieswithinthesplay
unit. Colluvial facies are dominant, particularly in the upper part and are composed of large andesite fragments, which are
generally subangular and lacking obvious abrasion features, suggesting that these are of local derivation. The gravel of the
fluvialfaciesofthisdepositconsistsofsmalltomedium-sizeexoticsubroundedpebblesthathavebeenmixedwiththe local
andesite boulders in the toes of the scree deposits. These facies are more prominent in the lower part of the succession. The
red sand facies occurs as thin cover, particularly in the distal part of the gravel units and increases in thickness in the lee of
the gravel splay.
The source of the fluvial gravel and its exotic clasts is threefold; firstly, by river transport of the palaeo-Vaal, secondly, by
erosion of nearby Dwyka sediments, still partly forming the north bank of the loop, and, thirdly, by reworking of higher level
and older gravels, remnants of which are still present on the hill at Canteen. The input of the coarse andesite clasts are linked
to scree slope deposits fed by exfoliation of the local bedrock on the hill at Canteen, filling the valley, particularly during the
latter stages of the occupation of this palaeoloop by the Vaal River. The upward-coarsening trend of this infill reflects the
gradual abandonment of the loop by the palaeo-Vaal and its inability to remove the coarse colluvium during those final
stages. A climatic change to drier periods, when the slopes were subjected to less frequent, but more intense floods, might
have had some influence on this textural trend.
Earlier Stone Age artefacts were noted in the area by early travellers, Colonel Bowker and Mary Elizabeth Barber, at the time
of the earliest diamond diggings. Subsequently, eminent prehistorians, including C. van Riet Lowe, the French archaeologist,
Abbé Henri Breuil, and J. Desmond Clark, visited and described the site. Breuil famously remarked that, “...not only are there
enough specimens [there] to fill a museum to overflowing but to build it of them also.” A portion of the site, known as Erf
91, was fenced off and declared a protected area in 1948, and an open-air display was created. It was not before the late
1990sto2000s,however,thatsystematicresearchonthearchaeology,nowknowntospanAcheuleantoHistorictimes,was
undertaken by Beaumont (1990, 2004), McNabb (2001, 2011), Forssman et al. (2010), Lotter et al. (2016) and Chazan et al.
(2013), among others (Beaumont and Morris 1990).
Figure 31.
Peter Beaumont showing a large Acheulean Stone Age artefact from Canteen Koppie.

35. 35
Diamond DEPOSITS
Cosmogenic burial-age dating has been used to establish a chronology that dates back at least 1.7 million years. The site
is phenomenally rich in artefacts, with Leader’s excavation through 7 m of deposit in a few squares producing over 15 000
artefacts.AparticularfocusofresearchonthearchaeologyoftheVaalgravelshereistheVictoriaWestmethod,whichallows
fortheproductionoflargeflakesthatareshapedintocleaversorhandaxes.TheVictoriaWestisapreparedcoremethodand
thereforecouldanticipatetechnologicaldevelopmentsfoundintheMiddleStoneAge.Itslimiteddistributioninwest-central
South Africa points to a role in the emergence of cultural behaviour in early hominins. Other noteworthy features include
the finding of a cache of specularite nodules in a Fauresmith context (at least some 300 000 years old) at the surface of the
gravel unit (Watts et al. 2016). The nearest source for this pigment is approximately 170 km west of the site. This find has
implications not only for the exceptionally early use of pigment as a behavioural practice but also for social networks across
thelandscapeatthattime.IntheHuttonsands,attheverytopofthesequence,areLaterStoneAgeandLateIronAgetraces,
testifyingtothepresenceofKhoe-SanandTswanacommunitiesincontactwiththenineteenthcenturydiggers(Chazanetal.
2013).Analysisandre-assessmentbySmithoftheenigmaticCanteenKopjeskull,foundatthesitein1925,showsthatit”falls
within the range of variation of Holocene Khoesan” (Smith et al. 2012), and is not archaic, as was previously thought.
Finally,ananalysisoftheminingrecordssuggeststhatthissplaydepositcouldhaveproducedbetween10000and15000 ct
of diamonds, equating to approximately 3 to 5 ct per 100 ton. The oversize clasts of the scree deposits would have acted as
important traps for the diamonds (De Wit 2008).
Figure 32.
Model of a kimberlite pipe
showing the schematic erosion
levels of selected pipes (after
Hawthorne 1975; Lynn et al.
1988).

36. IGC 2016
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Stop 16: Big Hole, Kimberley (28°44.348’S; 24°45.523’E)
AvisittotheBigHoleanditsassociatedMineMuseumprovidesanopportunitytoappreciateaprimarykimberliticsourceofthe
diamonds. Erosion of these ultrabasic volcanic plugs (kimberlite) released the diamonds for incorporation into the secondary
deposits. It is estimated that some 14 million ct have been mined from the Big Hole since its discovery (De Wit 1996; Lynn et
al.1998).Indeed,themodelofakimberlitepipe(Fig.32),asdescribedbyHawthorne(1975),isbasedonthediamondmines
inKimberley.Morerecently,andbasedonKarooxenolithswithinthesepipes,Hansonetal.(2006)havesuggestedareduced
level of erosion from the Kimberley pipes, which is more in agreement with the regional geomorphological analysis.
Drive from Kimberley to Bloemfontein.
Overnight in Bloemfontein
Saturday 27 August 2016
Flight from Bloemfontein airport (29°5.646’S; 26°18.029’E) to CapeTown.
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