Falcondo - Dominican Republic
The Falcondo operation
of Falconbridge Dominicana, C. por A. is located near Bonao in La Vega
Province, some 80 km north of Santo Domingo, the capital of the Dominican
Republic. The Dominican Republic occupies the eastern two thirds of the
island of Hispaniola, which is separated from the easternmost tip of Cuba
to the west by the 75 km wide Windward Passage. The operation has a production
capacity of 32 000 tpa of contained nickel as ferro-nickel (40% Ni, 60%
Fe). To date it has produced approximately 620 000 t of contained Ni since
the operation commenced in 1971. Ore is currently taken from six mining
areas, Larga, Loma Ortega, Fraser, Peguera, Taina and Guardarraya. These
six areas occur in a string of hills that extend for up to 15 km from the
processing plant and lie at between 200 and 600 m above sea level. The
lateritic ore below the overburden averages 7 m in thickness, but varies
from a few metres to 40 m. The deposits were developed over serpentinised
ultramafic rocks, with weathering and lateritisation commencing during
the Miocene uplift. Repeated uplifts have led to at least four physiographic
cycles and the development of a mature lateritic profile. The complete
profile is sub-divided from top to bottom into: Zone A - a chocolate-brown
limonite; Zone B - ochre brown limonite; Zone C - soft serpentine;
Zone D - hard serpentine; Zone E - serpentinised peridotite; and
Zone F - ultramafic rock. Zones A and F are rarely ore grade. The rocky
ore of Zones D and E account for 40% of the total ore reserves while limonite
ore of Zone B is 25% of the reserves. Nickeliferous serpentine is the major
crystalline phase of Zone C. In this zone and deeper, crystalline quartz
is found, particularly in fracture zones where it is often accompanied
by garnierite. The proven and probable reserve in 1999 was 68 mt @ 1.18%
Ni, with a further 19 mt @ 1.15% Ni in resource. The original pre-mining
reserve in 1971 was 66 mt @ 1.58% Ni. Annual production capacity is around
2.7 mt of ore. The bedrock is composed of extensively serpentinised ultra-mafics
with 0.15 to 0.35%, but averaging 0.28% Ni, 5.2% Fe, 0.02% Co. Cash operating
costs in 1998 were USD 1.82/lb Ni.
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Cerro Matoso - Colombia
The Cerro Matoso deposit in
Colombia is located some 20 km to the south-west of the town of Montelibano
in the Department of Cordoba on the western side of the Andes, and approximately
400 km north of the capital Bogota. It takes the form of a blanket on a
2500 m long oval shaped hill that rises some 200 m above the surrounding
countryside. The ore is capped by a layer of lateritic soil that is usually
overlain by a variable layer of ferruginous canga. The ore comprises a
zone of saprolite and saprolitised peridotite. The footwall is un-weathered
peridotite. In 1999 proven+probable reserves were more than 35 million
tonnes at 2.3% Ni using a 1.5% Ni cut-off, and up to 60 mt at a 1% Ni cutoff.
As such it is one of the highest grade lateritic nickel deposits in the
world. The mine and ferro-nickel plant are operated by Cerro Matoso S.A.,
a subsidiary of the Billiton group.
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Other Major
Deposits in the Caribbean
Punta Gorda / Moa Bay - Cuba
The Punta Gorda
and Moa Bay deposits are both in the Moa Bay area and are both part of
the same laterite sheet. Punta Gorda is a Cuban mine, while the Moa Bay
Operation is managed by the General Nickel Company S.A. (50% Sherritt International
Corporation - which has been involved in the project since 1990). These
deposits are part of a larger province of nickel laterites in eastern Cuba
that is estimated to contain at least 1200 mt @ 1.3% Ni (also including
Pinares de Mayari and Nicaro below). The total contained Ni resource of
Cuba is of the order of 27 mt. The proven + probable resource at Moa Bay
in 1998 was 60 mt @ 1.27% Ni. Production in 1997 amounted to 26 500 t of
Ni and Co from an acid pressure leach plant. The reserves at Punta Gorda,
which have been quoted at 310 mt @ 1.3% Ni, 0.11% Co, is treated by an
ammonia leach process. The ore is predominantly composed of a thick limonitic
layer that is mined by dragline. It overlies a thin saprolite that is unsuitable
for the acid leach processing (due largely to its high MgO content) and
hence is not mined nor is it included in reserves. In general the profile
comprises a thin (1 to 15 m thick dark brown iron cap of laterite and iron
concretions containing <1% Ni, but 50 to 55% Fe) overlying the main
limonite ore that may be around 1 to 40 m thick, averaging 10 m, of yellow
and yellow-brown ochreous laterite with 1.3 to 1.4% Ni, 0.10 to 0.13% Co,
45 to 50% Fe, 7% SiO2, 2% MgO. This in turn overlies around 1 to 15 m of
saprolite and sap-rock comprising yellow and yellow-green ochreous material
with disintegrated and partially decomposed serpentinite containing 1.5
to 1.8% Ni, 20 to 25% Fe, 30 to 35% SiO2, 15 to 20% MgO. Locally the profile
may be as thick as 50 m. The Moa Bay deposit is located on the eastern
margin of a 1500 km2 mass of serpentinised Cretaceous peridotites. The
original weathering surface had an irregular relief and laterites formed
on rises and slopes were periodically transported to lower zones, covering
earlier formed laterites. These transported laterites are well stratified
and sorted. Similar accumulations on slopes are not stratified and may
have been mud-slides. The lateritic processes have further modified the
layers of re-deposited laterite. This re-deposition resulted in an enhanced
thickness of laterite, in contrast to Pinares de Mayari which was deposited
on a higher peneplain.
NOTE: During the feasibility stage of the tour planning it was intended to include this deposit on the Nickel 2000 tour itinerary. However logisitical considerations precluded it. The details and literature references however were still provided to the tour participants as part of the tour information provided on lateritic nickel. Moa Bay, Punta Gordo and the other lateritic nickel deposits of Cuba were also covered by an expert workshop in Santo Domingo as part of the tour.
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Nicaro - Cuba
The Nicaro deposit
is located to the north of Moa Bay and has a reserve of just under 60 mt
@ 1.14% Ni, 0.1% Co. It lies adjacent to the undeveloped Pinares de Mayari
resource on the western side of the main Cretaceous peridotite mass and
has a resources of around 200 mt @ 1% Ni, 0.1% Co. Nicaro varies from Moa
Bay to the east in that it has a more varied and complex lateritic profile
with more nontronitic saprolite ore having been developed. In contrast
to the Moa Bay and Pinares de Mayari deposits, the main part of the serpentinite
mass at Nicaro was covered during the Tertiary by carbonate sediments.
This resulted in modification of the serpentinite by ground waters and
the development of carbonated serpentinite, but no change in the 0.12 to
0.24% Ni content. After the erosion of the carbonate sediments, lateritisation
proceeded normally near the surface, although at greater depths the presence
of carbonates in the serpentinites produced more alkaline conditions. This
has been interpreted as the main influence of the development of a nontronitic
zone with the bulk of the nickel ore. Iron is less well developed in this
zone with <20% Fe associated with 1 to 3% Ni. No Fe or Ni accumulations
are found below the nontronitic zone. Nicaro is also in a zone of well
developed valleys which have eroded, transported and re-deposited laterites
and saprolite which have an irregular and lensoid geometry. Four generalised
levels are defined at Nicaro, namely an upper 0 to 8 m thick dark brown
iron cap laterite with ferruginous concretions and 0.5% Ni, 43% Fe; a second
layer of yellow and yellow-brown ochreous laterites from 1 to 30 m thick
containing zones of both ore grade 1.3% Ni, 42% Fe and non-industrial 0.8%
Ni, 42% Fe; a third layer of yellow and yellow-green clay saprolites with
1.5% Ni, 16% Fe, containing soft grey-green serpentinite fragments; and
a lower 0 to 40 m thick irregular band of barren soft weathered green-grey
serpentinite overlying fresh bedrock.
NOTE: During the feasibility stage of the tour planning it was intended to include this deposit on the Nickel 2000 tour itinerary. However logisitical considerations precluded it. The details and literature references however were still provided to the tour participants as part of the tour information provided on lateritic nickel. Nicaro and the other lateritic nickel deposits of Cuba were also covered by an expert workshop in Santo Domingo as part of the tour.
![[Laterite Nickel Mining]](graphics/laterite.jpg)
