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August 2015
MODERN MINING
27
RUBIES
Haulage operations
underway at Montepuez.
The Gemfields-operated
mining fleet consists of six
excavators, 17 ADTs and 18
tipper trucks.
total rock handling amounted to 3,16 Mt, with
the ore mined amounting to 675 000 tonnes.
The stripping ratio is estimated at 3,4:1. Ruby
production to date is just over 16 million carats
at an average ore grade of 38,1 ct/t.
Although Mozambican rubies reportedly sell
for about half the price of comparable Burmese
(Myanmar) rubies, Gemfields says market rec-
ognition of Mozambique’s rubies has steadily
risen in recent years and the value has tripled.
Over 4 million carats have been sold in the
four auctions held so far by Gemfields, gener-
ating US$122,2 million with the average price
achieved for high quality sales being US$688/
ct and for low quality sales US$4/ct.
Montepuez has produced some exceptional
rubies, notably the 40-carat ‘Rhino Ruby’,
whose recovery was announced in November
last year. It was successfully sold at auction in
December 2014 although the price achieved
remains undisclosed (given the principles on
which Gemfields’ auctions are conducted).
More recently (in June this year), Gemfields
announced the discovery of a rare pair of match-
ing rubies with a combined weight of 45 carats,
which it described as an “extraordinary find”.
In terms of its Life of Mine (LoM) plan,
Montepuez is progressing from the bulk sam-
pling phase to full scale production. The
principal targets are achieving an annualised
processing rate of 1,3 Mt/a of ore by July 2016
and increasing the total mining capacity to
5,6 Mt/a by July 2017, objectives which SRK in
the CPR considers to be achievable and appro-
priate for the orebody as currently defined.
It is envisaged that a contract miner will be
brought in to provide sufficient waste strip-
ping capacity for 3 Mt/a with the balance of
waste movement being handled by Gemfields’
owner-operated fleet. The planned expansion
will also require upgrading the existing plant to
150 t/h capacity (operating at 120 t/h) plus the
construction of a new, permanent 250 t/h (oper-
ating at 200 t/h) process plant incorporating
washing, screening and DMS/optical sorting to
recover the rubies.
The new plant will produce a significant
quantity of fine tailings and will therefore
incorporate a fines thickening circuit. The
concept for tailings slurry handling includes
a number of concrete ponds into which the
thickened slurry will be deposited to allow
further settling and water removal. The ponds
will be used in continuous rotation. The intent
is that the settled muds will be excavated and
transferred to the old worked-out pits for final
disposal with the coarser waste material.
The projected LoM of Montepuez is 21 years
producing a total of 432 million carats. Projected
real cash flow (no discount rate applied) over
the LoM is estimated at US$2,76 billion. The
independent technical economic model pre-
pared by SRK shows a post-tax NPV of US$996
million based on a 10 % base case discount rate
and an IRR of 311,7 %. Required capex is esti-
mated at US$64 million over the first two years
and US$305 million over the LoM.
Regarding exploration, Gemfields has a
substantial programme planned for the next
few years in its 336 km
2
concession area.
Exploration to date – a total of 1 090 drill
holes, over 15 000 m in total, as well as 823
small-scale exploration pits – has only covered
around 36 km
2
of the concession. Two core
drills and one contracted auger drill are cur-
rently on site.
Apart from the Montepuez mine, Gemfields
– which is based in London – also has a 75 %
interest in the Kagem emerald mine near Kitwe
in Zambia (covered at length in our April issue
this year) and a 50 % interest in the Kariba ame-
thyst mine, also in Zambia. It is also the 100 %
owner of the Fabergé luxury goods brand.
Photos courtesy of Gemfields
Montepuez has
produced some
exceptional
rubies, notably
the 40-carat
‘Rhino Ruby’,
whose recovery
was announced
in November
last year.