NICKEL LATERITES

characteristics, classification and processing options

Charles ButtAugust 2007

CUBA

INDONESIA

AUSTRALIA

LATERITES SULPHIDES

NEW CALEDONIA

PHILIPPINES22oN

22oS

NICKEL DEPOSITS: LATERITES AND SULPHIDES

NICKEL LATERITE

• Regolith, derived from ultramafic rocks, that contains commercially exploitable reserves of nickel (and, commonly, cobalt)

i.e., an economic term, implying high grades and/or tonnages of Ni-rich material

• ultramafic rocks, >~2500ppm Ni Peridotite: 40-90% olivine + pyroxene Dunite: >90% olivine ophiolite, komatiite; layered intrusives (all ± serpentinized)

NICKEL SUPPLY: LATERITES AND SULPHIDES

A: Hydrous Mg-Ni silicate deposits (~35% of total resource)

Altered serpentines, népouite, “garnierite” in saprolite High grade: global mean 1.53% Ni Moderate to high relief; savanna, tropical rainforest

B: Smectite silicate deposits (~15% of total resource)

Clays (e.g., nontronite) in upper saprolite and pedolith Low grade: global mean 1.21% Ni Low relief; savanna, semi-arid

C: Oxide deposits (~50% of total resource)

Fe and minor Mn oxides, in upper saprolite and pedolith Low grade: global mean 1.06% Ni Most environments

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CLASSIFICATION OF NICKEL LATERITES

EAST PINARESCuba

Photo: Mick Elias

Oxide

GORONew Caledonia Oxide; some hydrous silicate

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CAWSEWestern Australia

Oxide

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CRBs021-01

Ni %0.08

0.20

1.26

0.46

0.47

0.19

0.25

Co %0.04

0.07

0.04

0.15

0.16

0.09

0.12

MgO %1.0

0.3

1.1

0.08

29.4

39.5

42.3

Fe %7.6

8.5

44.1

18.1

7.2

5.8

8.3

SiO %2 70.8

82.3

35.9

72.3

26.7

28.3

36.6

DuricrustMottled and

plasmic clays

Ferruginoussaprolite

Saprolite

Saprock

Bedrock

Mn oxides

ShearSilica

Mg discontinuity

CAWSE

Magnesite

Serpentinizeddunite

Shear

Mn oxides

OXIDE NICKEL LATERITE PROFILE: CAWSE

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PRINCIPAL NICKEL MINERALS

OXIDE DEPOSITS

Goethite Fe oxide (Fe,Al)O.OH 2% Ni, 0.2% Co Asbolan Mn oxide (Co,Ni)Mn2O4(OH)2.nH2O 16% Ni, >4% Co Lithiophorite (Al,Li)Mn2O4(OH)2.nH2O 1% Ni, ~7% Co

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PLATEAUNew Caledonia

Hydrous silicate; minor oxide

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PLATEAUNew Caledonia

Hydrous silicate

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CIRCENew Caledonia

Hydrous silicate “garnierite” ore

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C RC LEM EC R B s0 0 4-0 0

0

10

20

30

40

50

Verm iform and pisolitic dur icrust

Red plasm ic clay

Ferruginoussaprolite

Saprolite

Peridotite bedrock

N i %0.3

0.9

1.4

2.0-3.0

2.3

2.5

3.0

0.3

Iron c rust P iso liths

Red lim onite

Yellow lim onite

E arthy ore

Soft sapro lite

O re w ith boulders

Rocky ore

Fresh peridotite

D epth (m )

G arnierite

after Troly et a l., 1979

HYDROUS SILICATE (GARNIERITE) – OXIDE PROFILE

Oxide

Ni lizardite Serpentine (Mg,Ni)3Si2O5(OH)4 6.1% Ni Népouite 32.8% Ni 7Å garnierite 15.1% Ni Nimite Chlorite (Ni,Mg,Al)6(Si,Al)4O10(OH)8 16.9% Ni 14Å garnierite 3.3% Ni Falcondoite Sepiolite (Ni,Mg)4Si6O15(OH)2.6H2O 24% Ni Willemseite Talc (Ni,Mg)3Si4O10(OH)2 27.1% Ni 10Å garnierite 19.9% Ni Pimelite 15.7% Ni

HYDROUS NI-MG SILICATES

PRINCIPAL NICKEL MINERALS

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BULONGWestern Australia

Smectite silicate

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MURRIN MURRINWestern Australia

Smectite silicate

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MURRIN MURRIN Smectite silicateWestern Australia

magnesite

Photo: Martin Wells

SMECTITE SILICATE PROFILE

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SMECTITE DEPOSITS

Nontronite Smectite Na0.3Fe2(Si,Al)4O10(OH)2.nH2O 4% Ni

Minor goethite, asbolan

PRINCIPAL NICKEL MINERALS

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PROCESS ORE PRODUCT COMMENT

Smelting1859, New Caledonia

Hydrous silicate Ferro-nickelmatte

Energy intensive; (smelting ~1600ºC)

Caron process

Reduction & ammoniacal leach1944, Cuba

Oxide; hydrous silicate (Mg <4%)

Ni oxide; Ni briquettes Energy intensive (reduction ~700ºC) low Co recovery

High pressure acid leach (HPAL)1959, Moa Bay, Cuba

Oxide; smectite (Mg <4%)

Ni briquettes; electronickel; oxide, sulphide, carbonate

Less energy intensive. Plant & process problems

Enhanced high pressure acid leach (EPAL)

Hydrous silicate Ni-Co hydroxide Atmospheric leach after HPAL

Acid heap leach H2SO4

Atmospheric leach

H2SO4

HCl/MgCl2

Oxide; smectite

Oxide; smectite

hydrous silicate

Ni-Co hydroxide Lower capital cost;

Lower recoveries

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PROCESSING OPTIONS FOR NICKEL LATERITES

Oxide(or smectite)

Transition

Hydrous silicate

(after Elias 2001)

PROCESSING OPTIONS RELATIVE TO DEPOSIT TYPE

Hydrous silicate ore(“garnierite”; serpentine)Too costly for smectite

e.g., tumbling of boulder ore

1400 - >1600ºC; high energy cost

SiO2/MgO <2 or >2.5= ferronickel

SiO2/MgO 1.8-2.2= matte

~77% of total production in 2000 33% or less of new capacity

NICKEL LATERITE PROCESSING

Smelting

FEED

P ROCEESS

Drying

Upgrading

Reduction roast

Smelting

Converting

P RODUCT

Fe-Ni or Ni matte90% recovery

Ni: >2.0%Co: 0.04%Fe: 20%MgO: 25%

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High grade oxide ore, some hydrous silicate; tolerates more Mg than HPAL. Too costly for smectite.

~700ºC; high energy cost

Complex pyrometallurgical - hydrometallurgical process; high energy cost with lower recoveries than smelting and PAL.

No new plants anticipated

NICKEL LATERITE PROCESSING

Caron process

FEED

P ROCEESS

Reduction roast

Grinding, drying

Leach ammoniacal CO3

Cobalt separation

Ni carbonate precipitation

P RODUCT

Ni:94% recovery

Ni: 1.8%Co: 0.1%Fe: 25-40%MgO: <12.0%

Co:90% recovery

Calcining

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Oxide or smectite ore, low Mg and Al to reduce acid consumption

Upgrade oxide by screening to remove barren silica

High capital costs, with new plants having numerous teething problems in plant and process.

Product options include sulphides: Murrin2, Halmahera hydroxide: Ravensthorpe, Vermelhocarbonate: Cawse

NICKEL LATERITE PROCESSING

High pressure acid leaching

FEED

P ROCEESS

Leach H2SO4

Ore preparation

Acid plant

S

EnergyWash/neutralize

SX-EW or precipitateP RODUCT

Ni:94% recovery

Ni: 1.3%Co: 0.13%MgO: <5.0%

Co:90% recovery

240-270ºC; lower energy costcf Caron process

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Murrin Murrin

NICKEL LATERITE PROCESSING

Atmospheric leaching

FEED

Oxide ore (but, potentially, any ore type, including low grade hydrous silicate)

P ROCEESS

Agitate, heat and leach H2SO4

Ore preparation

Acid plant or excess from HPAL

S

EnergyWash/neutralize

SX-EW or precipitateP RODUCT

Ni (Co) hydroxide~80-90% recovery

Ravensthorpe, Gag Island: oxide, serpentine saprolite (hydrous silicate)Sechol: oxide, saprolite

Enhanced high pressure acid leaching (EPAL); 80-105ºC

Sechol/Jaguar tested HCl/MgCl2 leach at 80-105ºC. Process could also yield MgO and magnetite concentrate as products. Trial discontinued

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NICKEL LATERITE PROCESSING

Heap leaching

FEED

Potentially, any ore type, including low grade hydrous silicate and rejects

P ROCEESS

Heap, irrigate for 12-18 months

Ore preparation

Acid plant or excess from HPAL

S

EnergyWash/neutralize

P RODUCT

Ni (Co) hydroxide ~80% recovery

SX-EW or precipitate

Caldag, Nornico - oxide; Murrin Murrin - smectite

Crush; upgrade by screening to remove barren silica

Neutralize using low grade saprolite ore

Suitable for smaller deposits; low capex and opex

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From top of Heap 2 looking at Çaldağ mountainDemonstration precipitation plant

European Nickel plc 2006

200 m20 km

Çaldağ Heap Leach project, Turkey

Çaldağ

Izmir *

Istanbul

50 km

*

HPAL Atmospheric leach

Heap leach

Capital expenditure

$17-22 $13-16 $8-12

Operating expenditure

$2.50 $2.50 $2.50

$US/lb Ni

Source: Minara Resources, 2006

PROCESSING OPTIONS FOR NICKEL LATERITES

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NICKEL LATERITE PROCESSING: Summary and conclusions

1: Nickel laterites form ~ 75% of known Ni resources

2: By 2010, over 50% of Ni will be derived from NiL

3: Three main ore types: oxide, hydrous silicate, smectite; all products of humid weathering, ± later modification

4: “Traditional” processing (smelting, Caron) is generally very energy intensive

5: HPAL plants use less energy but require high capital expenditure and are yet to be fully optimized; best suited to large deposits

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6: Acid leaching at lower temperatures and ambientpressures offer lower capital expenditure (but lower recovery). Suited for treating lower grade ore and small or remote deposits

7: Better mineralogical characterization is needed tooptimize grade control, beneficiation and processing

NICKEL LATERITE PROCESSING: Summary and conclusions (continued):

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