Nickel Laterite Deposits Research Articles

Dehydroxylation and dissolution of nickeliferous goethite in New Caledonian lateritic Ni ore

Goethite is a major constituent in ferruginous soils in a lateritic nickel deposit on the Koniambo massif in New Caledonia, and dehydroxylation of nickeliferous goethite may occur naturally due to fire and during the processing of lateritic Ni ore. Goethite started to alter to hematite in 2 h of heating at 230–250 °C and had completely altered to hematite at 340 °C and higher temperatures. For most heated samples the rate of dissolution of Fe in 1 M HCl followed the cube root equation with a single straight line describing the data, however for samples where both goethite and hematite were present the data did not conform to this equation. There was an approximately 7 fold increase in the rate of dissolution for samples heated to 340 °C which can be accounted for by the increase in surface area (2-fold) due to the development of micropores and the increase of structural defects in poorly ordered hematite structures (protohematite and hydrohematite) (3.5-fold) formed by partial dehydroxylation of goethite. For heated samples Ni, Cr, Al, Co and Mn showed congruent dissolution with iron indicating uniform incorporation of these metals in the structures of the iron oxides and complete retention of these metals in crystals during the goethite to hematite transition. V and Cu showed only partial dissolution (i.e. noncongruent dissolution) indicating that some V and Cu may be associated with another less soluble mineral (e.g. ilmenite).

Lateritization processes of ultramafic rocks in Cretaceous times: The fossil weathering crusts of mainland Greece

The lateritic weathering crusts exposed in mainland Greece were developed on ophiolitic ultramafic lithologies during lower Cretaceous times. The lateritic profile consists of four zones: bedrock, saprolite clay (nontronite) and goethitic. The profiles show large variations in thickness, continuity, mineralogy and chemical characteristics. They are broadly similar to clay nickel laterite deposits. The uppermost gravelly ferruginous sector was eroded and the material reworked and redeposited partly on the lateritic crust. Silcrete layers, characteristic of groundwater silcretes, were formed into the clay and goethitic zones. Significant supergene nickel enrichments occur in the clay and saprolite zones, indicating that water moved downward to a very low water table. The structure and mineralogy of the weathering crusts indicates that environmental conditions were likely to have been dominated by alternating wet and dry periods.

Clay mineralogy of the nickel laterite ore developed from serpentinised peridotites at Murrin Murrin, Western Australia

Samples from the saprolite and extensive smectite zone (up to 25 m thick) of the Murrin Murrin lateritic nickel deposit, developed from serpentinised peridotites, were studied using optical microscopy, XRD, SEM and TEM-EDX. In the saprolite zone, the initial mesh-texture of the parent rock is still well preserved. The mineralogy is dominated by serpentine, smectite and maghemite. Two kinds of smectites occur in this zone: saponites and smectites with chemistries intermediate between two dioctahedral end-members (Fe nontronite, Fe montmorillonite) and a trioctahedral one (Mg + Ni saponite). In the smectite zone, serpentine and saponite completely disappear, however some relicts of the initial mesh-texture exist. Smectite and maghemite are the dominant minerals and goethite appears at the top of this zone. Smectites from the smectite zone have a complex chemistry which appears intermediate between four dioctahedral end-members (Fe Nontronite, Fe montmorillonite, Al beidellite, Al montmorillonite) and a trioctahedral one (Mg + Ni saponite). Smectites in fissures exhibit a greater variability in Al vs Fe + Cr content than smectites from plasma; this suggests a supply of Al by the percolating fluids. Nickel, essentially concentrated in the smectite zone (1.3 wt%), is located in the octahedral sheets of the plasma and fissure-smectites with Ni content up to 0.30 per half unit-cell. The oxygen and deuterium isotopic compositions of the smectites show that they crystallised at low temperature in contact with meteoric fluids. The δ18O values of Murrin Murrin smectites are negatively correlated with their Fe + Cr content.

Estimativa da abundância de minerais do depósito de níquel laterítico da mina fazenda por espectrorradiometria

The aim of the paper is to develop a method to estimate the relative abundance of pimelite in relation to goethite and asbolan present in the lateritic nickel deposit (Niquelândia - GO), from reflectance spectroscopy data. Spectral mixtures, of macroscopic and microscopic (intimate) type were analysed. The behavior of intimate mixture was analyzed by known amounts of the minerals and its respective measure in the laboratory. The macroscopic mixtures were made by mathematical simulation using linear functions. Both cases were employed index based on the Mg-OH spectral feature present in the pimelite. Mixture index and the band depths were used for spectral analyses. The index values were adjusted with the known amounts found in the sample by linear and not linear regressions according to the case. Thus, extreme situations of mixtures had been established. The results show that the developed model is appropriate to estimate relative concentration of pimelite. This spectral analysis method has the advantage to obtain a remote mineralogical characterization of lateritic nickel horizon profile.

Traditional and New MIP Models for Production Scheduling With In-Situ Grade Variability

Mixed integer programming (MIP) has become a common approach for optimizing production schedules of open pit mines since the 1960s. However, MIP has been found to be limited by: (a) feasibility in generating optimal solutions with practical mining schedules; and (b) inability to deal with in-situ variability of orebodies. In looking into these shortcomings, this paper presents a general production scheduling method for multi-element deposits in open pit mines. The method is subsequently used to optimize the production schedule in a nickel laterite deposit. The application confirms the weaknesses of MIP formulations mentioned above. An alternative MIP formulation is then presented and applied to the same deposit. The results of the new formulations show that the new MIP model can overcome the above shortcomings and generate practical mining schedules with a higher chance of achieving planned production targets than traditional MIP schedules.

Nickel Laterites: A Review

ABSTRACT Nickel laterite deposits are formed by the prolonged and pervasive weathering of Ni silicate-bearing ultramafıc rocks, generally in tropical to subtropical climates. The deposits can be further classifıed as hydrous silicate deposits (e.g., SLN Operations, New Caledonia), clay silicate deposits (e.g., Murrin Murrin, Australia), and oxide deposits (e.g., Moa Bay, Cuba; Cawse, Australia) on the basis of the ore mineralogy. The physical and chemical nature of a nickel laterite deposit is a function of many factors, including the composition of the parent rock, the tectonic setting, climate, topography (specifıcally, laterite morphology), and drainage. Nickel laterite ore is extracted using both selective and bulk mining methods in open cast mining operations. The mined ore has traditionally been processed either by hydrometallurgical leaching technology (pressure acid leach or Caron processes) to produce oxides of nickel and cobalt or mixed Ni-Co sulfıdes for market, or by pyrometallurgical smelting to produce ferronickel granules or nickel matte. However, recent advances in high-pressure acid leaching and continued testing of atmospheric leach technology should lead to a reduction in overall operating costs and increased exploitation of Ni laterite resources in the future.

Comments on the paper “Ochreous laterite: a nickel ore from Punta Gorda, Cuba” by Oliveira et al.

The paper, “Ochreous laterite: a nickel ore from PuntaGorda, Cuba,” by Oliveira et al. (2001) presents acharacterization of oxidized nickel ore from the PuntaGorda deposit in the Moa district (eastern Cuba). Theauthors assume that the nickel ore derives from an ophioliticassociation (serpentinized ultramafic rocks, olivine gabbros,and plagiogranites) strongly affected by lateritization. Theynote that ‘no extensive study has so far been published aboutthe Ni mineralization in regard to the mineralogical andchemical nature of the ore’ and reach the conclusion thatnickel is associated with goethite and cobalt with manga-nese minerals. The authors find two ore types, Ni-rich(1.56–2.06%) and Ni-poor (0.24–0.96%), and infer that thetwo types are related to differences in the parent rocks.Oliveira et al. contend that the Ni-rich ore derives fromperidotites containing Ni-bearing orthopyroxenes and thatthe Ni-poor ore forms from peridotites containing Al-clinopyroxene depleted in Ni. Despite their interestingattempt, we believe these points require some criticalcomments that point to possible alternative interpretations.First, the Moa-Baracoa ophiolitic massif consists of alower unit of mantle tectonites made up of serpentinizedharzburgite with minor dunite, ‘impregnated peridotite’(plagioclase- and clinopyroxene-bearing peridotite), wehr-lite, and pyroxenite and a crustal sequence composed oflayered gabbro (olivine gabbro and gabbronorite) anddiscordant pillowed basalts and sediments of the Quivija´nFormation (Guild, 1947; Wadge et al., 1984; Ri´os andCobiella, 1984; Fonseca et al., 1985; Iturralde-Vinent, 1989,1996, 1998; Keer et al., 1999; Proenza et al., 1999a,b).Towards the top of the mantle tectonites, the harzburgitecontains increasing amounts of dunite, gabbro sills, andchromitite, which form elongated pseudotabular bodiesparallel to the foliation of the host harzburgite, as well asdiscordant dikes of gabbro and pegmatitic gabbro (Fig. 1).This upper zone has been considered as forming part of theMoho Transition Zone (MTZ) (Proenza et al., 1999a,b).Second, Oliveira et al. (2001) ignore many publishedstudies on the geological, mineralogical, and chemicalcharacteristics of the Cuban lateritic nickel deposits(Kudelasek et al., 1967; Vera, 1979; Formell and Oro,1980; Vershinin et al., 1984; Quintana-Puchol, 1985;Ostroumov et al., 1985, 1987; Cordeiro et al., 1987;Rojas-Puro´n et al., 1993; Rojas-Puro´n and Carballo, 1993;Capote et al., 1993; Almaguer and Zamarzry, 1993;Rojas-Puro ´n and Beyris, 1994; Rojas-Puron and Orozco,1995; Almaguer, 1995, 1996; Lavaut, 1998). These studiescontain extensive results about the Ni mineralization in theMoa district and conclude that Ni in ochreous laterite isassociated with goethite and Co with manganese minerals(asbolanes).Third, the differences in the mineralogical and chemicalcomposition of the Ni-rich and Ni-poor ores cannot beexplained by the presence of Ni-bearing orthopyroxene orNi-depleted, Al-rich clinopyroxene in the parent rock, asOliveira et al. (2001) conclude, because the Moa peridotitesare made up of only harzburgites and dunites (Proenza et al.,1999a,b), neither of which contains significant clinopyrox-ene. The average forsterite and NiO content of olivine in theharzburgites is 91.0 and 0.39 wt%, respectively, whereas indunites, these values are 91.5 and 0.38 wt% (Table 1). TheNi content of orthopyroxene is very low (NiO , 0.1 wt%),usually below the detection limit of the electron microprobe(Table 1). However, clinopyroxene-bearing harzburgites arevery scarce in the whole Moa-Baracoa massif. Therefore,the Ni-rich ore can only derive from harzburgite and dunite

Mineralogy and geochemistry of the pliocene iron-rich laterite in the Vatera area, Lesvos Island, Greece and its genesis

A nickel laterite deposit occurs in the Vatera area of Lesvos Island, Greece, and is transgressively developed on serpentinized basic rock (norite). The overlying sedimentary rocks include marls and marly limestones with sandstone intercalations and belong to the Pliocene sediments. The following lateritic zones are defined from the bottom to top layers: a) bedrock (norite); b) serpentinized zone; c) goethitic zone. The bedrock consists of the following primary minerals: basic plagioclase, orthopyroxenes and clinopyroxenes. The serpentinized zone includes clinochrysotile, lizardite, antigorite clinoenstatite, calcite and dolomite while in the goethic zone there are goethite, quartz, pyrite, chromite, dolomite. A12O3, Fe2O3, CaO, Na2O, K2O, Ba, Sr, Ni, C and S are enriched in the goethitic zone. Nickel enrichment is related to the formation of nickeliferons minerals substituting for Mg or/and Fe in the goethite and pyrite. Enrichment of Ni in the matrix may be due to the presence of amorphous Ni-silicates (pimelite). There is a significant change (decrease) in the concentration of Ni from the top to bottom parts of the laterite formation, indicating that there was no tendency to migrate downwards (immature laterite). A second support of the immaturity of the Vatera laterite is the incomplete oxidation of ferrous iron to form ferric iron hydroxides. Under tropical/subtropical conditions, which dominated from the end of Miocene to the Pliocene the norite rocks of the Vatera area altered in response to reaction with acid solutions enriched in CO2. Due to hydrolysis and oxidation of pyroxenes, Mg2+, P4SiO4 and Ni2+ were removed in the continental acid solutions.

AS FASES PORTADORAS DE NÍQUEL DO MINÉRIO LATERÍTICO DE NÍQUEL DO VERMELHO, SERRA DOS CARAJÁS (PA)

In the lateritic nickel deposit of Vermelho, Serra dos Carajas-PA, two types of ore can be recognized: the silicated ore at the bottom of the weathering profile, and the oxidized ore at the top. The mineralogical composition of the silicated ore (average grade = 1.8%wt NiO) consists largely of serpentine, chlorite and spinels, with quartz and goethite in minor amounts. Serpentine and chlorite are the main nickel-bearing minerals, being Ni about equally distributed between the two phases (2-3%wt NiO). The oxidized ore (average grades 1.2%wt NiO) is composed predominantly of goethite, containing also chlorite, spinels and quartz. In this case, nickel is highly concentrated in chlorite (average 12%wt NiO), whereas in goethite it ranges between 0,9 and 1,7%. As a result, the presence of chlorite, even in minor quantities, is important in raising the grade of the oxidized ore. Locally, higher grades of ore can also be due to the presence of nickeliferous smectites.

Lateritic nickel deposits of Brazil

Many nickel deposits are known in Brazil, accounting for about 350 · 106 tons of ore with an average of 1.5% Ni. All are of the lateritic type. These deposits are scattered throughout the country, being rarer in the Northeastern Region and in the South, below 25 °S latitude. They are mainly associated with mafic-ultramafic massifs of large dimensions and ultramafic alkaline complexes, and occur in climatic regions of contrasting seasons. The weathering profile developed over the fresh rock consists, from bottom to top, of the following horizons: altered rock, coarse saprolite, argillaceous saprolite, ferruginous saprolite and lateritic overburden. The thickness of each horizon varies from one deposit to another, the whole profile generally exceeding 20 m. The saprolitic horizons with inherited minerals (serpentine, chlorite) or neoformed minerals (smectites) constitute the silicated nickel ore and are thicker were climatic conditions are drier; the ferruginous upper horizons made up of iron oxide-hydroxides are more developed in more humid regions. In Brazil, the silicated ore generally prevails over the oxidized ore. The main Ni-bearing minerals are serpentine, smectite, garnierite and goethite. The lateritic nickel deposits of Brazil may be correlated with two erosion surfaces, corresponding to the Sul Americano (Lower Tertiary) and Velhas (Upper Tertiary) levelling cycles. The degree of dismantling of the higher and more ancient surface and the consequent development of the Velhas Surface control the position of the nickel accumulation in the landscape. Thus, the deposits may be found either in the lowlands or in the highlands, where they are always covered by a silcrete layer. The alteration profiles in the Brazilian lateritic nickel deposits are broadly similar to those described elsewhere in the world. However, they present two characteristic features: the silicated ore prevails over the oxidized ore, and a silicified layer covers the profies developed on the highlands.

The availability of primary nickel from the market economy countries

The US Bureau of Mines has determined the potential availability of nickel from 36 deposits or districts in 16 market economy countries (MECs). More than 95% of production in MECs was analysed. The study indicates the quantity of nickel available in resources and potential annual production at net production costs and on a total cost basis with a 0% and a 10% discounted cash flow rate of return (DCFROR). The properties included in this study contain approximately 33 million tonnes of recoverable nickel. About 26 million tonnes of nickel is potentially recoverable from nickel laterite deposits, of which 4.5 million tonnes can be produced at $2.50/lb or less with a 0% DCFROR. Approximately 7 million tonnes of nickel is potentially recoverable from nickel sulphide deposits of which about 6.3 million tonnes could be produced at $2.50/lb or less at a 0% DCFROR. Sensitivity studies indicate that the total cost of producing nickel from laterite deposits is most sensitive to increases in energy costs, and that the total costs of producing nickel from sulphide deposits is most sensitive to increases in labour costs and by changes in byproduct revenues.

Metallogeny and tectonic development of the Tasman Fold Belt System in Queensland

The northern part of the Tasman Fold Belt System in Queensland comprises three segments, the Thomson, Hodgkinson- Broken River, and New England Fold Belts. The evolution of each fold belt can be traced through pre-cratonic (orogenic), transitional, and cratonic stages. The different timing of these stages within each fold belt indicates differing tectonic histories, although connecting links can be recognised between them from Late Devonian time onward. In general, orogenesis became younger from west to east towards the present continental margin. The most recent folding, confined to the New England Fold Belt, was of Early to mid-Cretaceous age. It is considered that this eastward migration of orogenic activity may reflect progressive continental accretion, although the total amount of accretion since the inception of the Tasman Fold Belt System in Cambrian time is uncertain. The Thomson Fold Belt is largely concealed beneath late Palaeozoic and Mesozoic intracratonic basin sediments. In addition, the age of the more highly deformed and metamorphosed rocks exposed in the northeast is unknown, being either Precambrian or early Palaeozoic. Therefore, the tectonic evolution of this fold belt must remain very speculative. In its early stages (Precambrian or early Palaeozoic), the Thomson Fold Belt was probably a rifted continental margin adjacent to the Early to Middle Proterozoic craton to the west and north. The presence of calc-alkaline volcanics of Late Cambrian Early Ordovician and Early-Middle Devonian age suggests that the fold belt evolved to a convergent Pacific-type continental margin. The tectonic setting of the pre-cratonic (orogenic) stage of the Hodgkinson—Broken River Fold Belt is also uncertain. Most of this fold belt consists of strongly deformed, flysch-type sediments of Silurian-Devonian age. Forearc, back-arc and rifted margin settings have all been proposed for these deposits. The transitional stage of the Hodgkinson—Broken River Fold Belt was characterised by eruption of extensive silicic continental volcanics, mainly ignimbrites, and intrusion of comagmatic granitoids in Late Carboniferous Early Permian time. An Andean-type continental margin model, with calc-alkaline volcanics erupted above a west-dipping subduction zone, has been suggested for this period. The tectonic history of the New England Fold Belt is believed to be relatively well understood. It was the site of extensive and repeated eruption of calc-alkaline volcanics from Late Silurian to Early Cretaceous time. The oldest rocks may have formed in a volcanic island arc. From the Late Devonian, the fold belt was a convergent continental margin above a west-dipping subduction zone. For Late Devonian- Early Carboniferous time, parallel belts representing continental margin volcanic arc, forearc basin, and subduction complex can be recognised. A great variety of mineral deposits, ranging in age from Late Cambrian-Early Ordovician and possibly even Precambrian to Early Cretaceous, is present in the exposed rocks of the Tasman Fold Belt System in Queensland. Volcanogenic massive sulphides and slate belt-type gold-bearing quartz veins are the most important deposits formed in the pre-cratonic (orogenic) stage of all three fold belts. The voicanogenic massive sulphides include classic Kuroko-type orebodies associated with silicic volcanics, such as those at Thalanga (Late Cambrian-Early Ordovician. Thomson Fold Belt) and at Mount Chalmers (Early Permian New England Fold Belt), and Kieslager or Besshi-type deposits related to submarine mafic volcanics, such as Peak Downs (Precambrian or early Palaeozoic, Thomson Fold Belt) and Dianne. OK and Mount Molloy (Silurian—Devonian, Hodgkinson Broken River Fold Belt). The major gold—copper orebody at Mount Morgan (Middle Devonian, New England Fold Belt), is considered to be of volcanic or subvolcanic origin, but is not a typical volcanogenic massive sulphide. The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusives of the transitional tectonic stage of the three fold belts, particularly the Late Carboniferous Early Perman of the Hodgkinson—Broken River Fold Belt and the Late Permian—Middle Triassic of the southeast Queensland part of the New England Fold Belt. In general, these deposits are small but rich. They include tin, tungsten, molybdenum and bismuth in granites and adjacent metasediments, base metals in contact meta somatic skarns, gold in volcanic breccia pipes, gold-bearing quartz veins within granitoid intrusives and in volcanic contact rocks, and low-grade disseminated porphyry-type copper and molybdenum deposits. The porphyry-type deposits occur in distinct belts related to intrusives of different ages: Devonian (Thomson Fold Belt), Late Carboniferous—Early Permian (Hodgkinson—Broken River Fold Belt). Late Permian Middle Triassic (southeast Queensland part of the New England Fold Belt), and Early Cretaceous (northern New England Fold Belt). All are too low grade to be of economic importance at present. Tertiary deep weathering events were responsible for the formation of lateritic nickel deposits on ultramafics and surficial manganese concentrations from disseminated mineralisation in cherts and jaspers.

The geology and mineral resources of Sierra Leone

Sierra Leone forms the central part of the sundered West African craton whose counterpart forms the Guyana Shield of northern South America. Three Archean to early Proterozoic thermotectonic events and the early Phanerozoic Pan-African orogeny preceded the breakup of the original craton in the early Jurassic by rift faulting and the intrusion of tholeiitic magmas to form new oceanic crust which accompanied the opening of the Atlantic ocean.The Archean rocks of Sierra Leone consist of a granitic basement containing elements of early sedimentary and mafic formations and a group of supracrustal greenstone belts with banded ironstone and detrital sediments. These are mineralized with gold, chromite, tin, copper, nickel, antimony, arsenic, and iron ores and are intruded by molybdenum-bearing granites. Lateritic weathering and alluviation has led to economic concentrations of diamonds, bauxite, and lateritic iron ores and to heavy mineral concentrates, particularly rutile. Prospects for lateritic nickel deposits appear to be good.Little exploration has been carried out in the poorly exposed Rokel River Group of late Proterozoic age. This formation and also the Ordovician (?) Saoinya Scarp Group contain glacial sediments in their lower horizons. The Triassic-Lower Jurassic Free-town Layered Basic Complex lies upon the continental margin and was formed by successive pulses of basic magma which formed a rhythmic sequence of troctolite, gabbro, and anorthosite which in some cases ended with an iron-enriched ilmenite-magnetite horizon and acid veining. Some alluvial platinum has been won from this complex, but the source rock has not yet been identified.Kimberlite dikes were emplaced in the Cretaceous period and have been the sources of the country's diamond mining industry. The Tertiary and Pleistocene sediments are known to contain horizons carrying lignite and ceramic clays and may also contain exploitable concentrations of other minerals.

Criteria and problems in estimating global lateritic nickel resources

Although two-thirds of the present nickel production is derived from nickel sulfides, lateritic nickel reserves are estimated to be around three times as large as those of sulfides. This discrepancy is largely caused by the mineralogical complexity of lateritic nickel which precludes low-cost beneficiation by conventional physical methods. Nevertheless, lateritic nickel reserves are bound to become increasingly important because of expected metallurgical advances. Lateritic nickel deposits were formed from peridotitic rocks on peneplaned surfaces during a tropical or subtropical climate. The most important deposits were formed during the Tertiary and the lateritization process still continues in deposits situated in the present tropical or subtropical belts. Other deposits, like those in East Europe and Greece, were formed during much older periods (Palaeogene-Cretaceous). The various types of lateritic nickel deposits, covered or uncovered,in situ or transported, are listed and their characteristics briefly mentioned. Large differences exist in depth, grade, specific gravity, and mineralogical composition—the latter especially in the nickel silicate section as opposed to the overlying limonitic section. These large differences exist even within one individual mining area. Because of the mineralogical complexities and highly irregular boundaries of lateritic nickel deposits (especially the upper and lower boundaries of the nickel silicate section), thorough studies are required to determine the mineralogical composition and ratios of the components. Only then may it be possible to specify with confidence the most suitable metallurgical process which has a strong bearing on the cost and consequently the viability of the deposit. This condition makes the exploitability rating in the McKelvey classification diagram relatively more difficult. Because of the quickly changing geological attributes of deposits even within limited areas, it seems necessary to develop various deposit models for many, if not most, individual metallogenic regions. It does not seens justified or practical to use estimation methodologies based on straight extrapolation. This is especially the case when dealing with the young uncovered type of deposit which constitutes the bulk of global resources. Consequently methodologies no. I (areal value estimation. Cargill, Meyer, Picklyk, Urquidi, 1977) and no. 2 (volumetric estimation) are not considered suitable. It is thought that methodology no. 3 (abundance estimation) in conjunction with no. 5 (Delphi estimation) would work satisfactorily but, as could be expected, the most meaningful results should come from a combination of methodologies nos. 4 (deposit modeling), 5 (Delphi estimation), and 6 (integrated synthesis). A classification of leteritic nickel deposit types is proposed.

The Exploration of the Nickel Laterite Deposits in Irian Barat, Indonesia

Nickel-bea rin g la terites developed in-situ on nickel-bearing peridotites were examined during the period 1969- 1971 at a number of loca lities in the Cyclops and Waigeo areas in Irian Barat, I nd ones ia . The lateri tes occur in both forested and unforested areas and as plateau and hill-sid e ty pes of deposits. The di stribution of chemical elements within the profile is similar to other tropica l nickel laterite deposits, i.e. , concentration of Al zOa and Fe in the nea r surface layers with an accompanying depletion of Si02 and MgO and concentration of nickel in the low iron portion of the profile. Exploration was by drilling (hand augers, mechanica l a uge rs a nd coring drill s) and tes t pits. Through 1971 more than 50,000 meters of drilling a nd testpitting were completed. Samples were a nalyzed for Ni, Co a nd Fe at PTPNI's chemica l labora tory on Waigeo Island. All drilling information, chemica l anal yses and mining class ifi cations are being analyzed by data processing techniques. In late 1971 a 12,000 ton bul k sa mple was coll ected on Gag Island and shipped to Fort Saskat­ chewan, Canada for testing and eva lu ation studies .

An exploration program for nickel in the southeastern United States

During 1958 and 1959 an exploration program for lateritic nickel deposits was carried out in the Blue Ridge and Piedmont crystalline provinces of the southeastern United States. In the course of the investigation information was compiled on various known and possible ultramafic bodies within the area. An extensive program of field exploration was carried out, including geologic mapping and sampling of ultramafic rocks and their overlying soils. Ultramafic rocks were found to contain primary nickel in amounts up to 0.4 percent and commonly carried about 0.2 percent nickel. Residual soils, lateritic in character, were found to as much as fifty feet or more in thickness, and contained nickel to as much as 1 percent or more. Considerable numbers of ultramafic bodies were examined in outcrop, a few of which would have been large enough for development of economically interesting tonnages of lateritic ore. While the requisite conditions for a lateritic nickel deposit were found to exist in the southeastern United States, they were not all met in one locality, and further search for such deposits was considered to be economically unattractive.