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September 2015
MODERN MINING
47
DIAMONDS
the south of the Jwaneng diamond mine.
In his presentation at
the conference, Daniels
recounted how De Beers in
the 1950s and 60s, under
the guidance of the late Dr
Gavin Lamont, changed
from panning samples to
grid samples. This change, he
said, initially resulted in the dis-
covery of Orapa and Jwaneng.
Falconbridge introduced aero-
magnetic surveys over areas
where there were indicator
anomalies but with thick sand,
an approach which subsequently
resulted in the discovery of the
Tsabong and Kokong kimber-
lite fields. This was followed
up by large scale regional
soil sampling using a heli-
copter over the central parts
of Botswana which resulted
in the discovery of the Gope (GO25) pipe in
1981 (which has now been developed by Gem
Diamonds as the Ghaghoo diamond mine).
According to Daniels, the discoveries of the
KX36 kimberlite in the Central Kalahari (by
Petra) and the Thankane-01 kimberlite to the
west of Jwaneng (by De Beers) were a result of
increasing the sample sizes from the standard
20 litres to 200 litres and 100 litres respectively.
He pointed out that the easy days of finding sig-
nificant concentrations of kimberlite indicator
minerals (KIMs) were probably over. He also
showed (using examples from Botswana) that
the minimum lead time from commencing an
exploration programme to making a kimberlite
discovery was five years, and often much lon-
ger. The only exceptions to this were GO25 and
the Martin’s Drift (Lerala) kimberlites.
Refuting the conventional wisdom that
geophysics and drilling were the most signifi-
cant aspects of diamond exploration, Daniels
predicted that future kimberlite discoveries
would largely depend on soil sampling rather
than the application of regional geophysics.
The key to future discoveries he said would be
a greater understanding of the surface textures
of individual KIMs as opposed to significant
numbers of KIMs in individual samples. He
commented that a single KIM with primary
surface textures constituted an anomaly that
warranted following up.
Four historical KIM soil anomalies of sig-
nificance in Botswana remained unexplained,
said Daniels. He told conference delegates that
Pangolin Diamonds held the exploration rights
over three of these anomalies and was currently
conducting extensive soil sample programmes
over these areas. He noted that Pangolin had
announced the recovery of four diamonds,
numerous picro-ilmenites, garnets, clinoprox-
enes and a mantle xenolith fragment from soil
samples from the Malatswae project, which is
situated to the south-east of the OKF.
The recovery of diamonds from soil samples
in Botswana is a rare occurrence and Pangolin
believes it is on the right track for the discov-
ery of diamondiferous kimberlites. Speaking
to
Modern Mining
at the conference and elab-
orating on his presentation, Daniels said that
a large number of the KIMs recently reported
had primary surface textures suggesting close
proximity to source. He said the chemical com-
position of the ilmenites recovered from the
Malatswae area was distinct from the ilmen-
ites from Orapa and indicated that Pangolin
was sampling a different kimberlite field. He
told
Modern Mining
that he was “quietly confi-
dent” that the detailed sampling grids currently
underway at the Malatswae project would lead
to several kimberlite discoveries in the near
future for Pangolin.
Since the Gaborone conference was held,
Pangolin has provided further updates of
its progress at Malatswae, the latest (dated
12 August) reporting that it has received posi-
tive results from a ground penetrating radar
(GPR) survey over its palaeo-alluvial diamond
target within the project area and from two GPR
surveys over two kimberlite targets.
Photos courtesy of Pangolin Diamonds
Selection of picroilmenite
from a single Malatswae
soil sample, showing fragile
reaction rims partially to
completely preserved on the
grains. The largest grains
exceed 2 mm.
The key to future
discoveries will
be a greater
understanding
of the surface
textures of
individual KIMs
as opposed
to significant
numbers of KIMs
in individual
samples.