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Ore from the Jinzhulong Ta–Nb deposit was processed using a combination of gravity concentration and magnetic separation to upgrade the columbite–tantalite fines. Two flowsheets, namely for gravity concentration–magnetic separation (the conventional flowsheet) and magnetic separation–gravity concentration (the novel flowsheet), are proposed herein, and the factors affecting the performance of gravity/magnetic separation were studied to optimise the flowsheets. Compared with the conventional flowsheet, the novel flowsheet was more effective for columbite–tantalite beneficiation and beneficial to the comprehensive recovery of nonmetallic minerals. In the novel flowsheet, the sample is ground to size of P80 = −74 micron then fed into a combination of a low-intensity wet drum magnetic separator and pulsating high-gradient magnetic separator to reject nonmagnetic gangue minerals while preconcentrating the paramagnetic columbite–tantalite; the high-gradient magnetic separation concentrates were screened into three size fractions and further upgraded by gravity concentration. The enrichment ratios for Ta2O5 and Nb2O5 were 403.8 and 385.6, respectively. (Authors.), Ore from the Jinzhulong Ta–Nb deposit was processed using a combination of gravity concentration and magnetic separation to upgrade the columbite–tantalite fines. Two flowsheets, namely for gravity concentration–magnetic separation (the conventional flowsheet) and magnetic separation–gravity concentration (the novel flowsheet), are proposed herein, and the factors affecting the performance of gravity/magnetic separation were studied to optimise the flowsheets. Compared with the conventional flowsheet, the novel flowsheet was more effective for columbite–tantalite beneficiation and beneficial to the comprehensive recovery of nonmetallic minerals. In the novel flowsheet, the sample is ground to size of P80 = −74 micron then fed into a combination of a low-intensity wet drum magnetic separator and pulsating high-gradient magnetic separator to reject nonmagnetic gangue minerals while preconcentrating the paramagnetic columbite–tantalite; the high-gradient magnetic separation concentrates were screened into three size fractions and further upgraded by gravity concentration. The enrichment ratios for Ta2O5 and Nb2O5 were 403.8 and 385.6, respectively. (Authors.)

The Yichun Ta-Sn-Li deposit occurs within the 9.5-km2 Yashan Igneous Complex, which is made up of felsic, peraluminous intrusions including two-mica, Li-mica, and topaz-lepidolite granites. The topaz-lepidolite granite forms a thin sheet confined to the upper part of the Li-mica granite and is separated from the host metasediments by a marginal pegmatite. The topaz-lepidolite granite is characterised by the presence of snowball textures in which quartz, K-feldspar, and topaz phenocrysts contain albite laths and rare lepidolite and columbite arranged along growth zones. Minor and accessory phases in the topaz-lepidolite granite include amblygonite, cassiterite, columbite-tantalite, microlite, wodginite, zircon, monazite, and pollucite. It is proposed that early crystallisation of the Li-mica granite led to the formation of a Si-poor, Al-, Na-, and flux-rich boundary layer whose low viscosity and density allowed effective separation from the remaining melt and crystals. This melt concentrated incompatible elements including tin and tantalum and accumulated in the upper part of the magma chamber where it crystallised the sheet-like bodies of marginal pegmatite and topaz-lepidolite granite. The uppermost part of the topaz-lepidolite granite consists of aplite and overlying quartz lepidolite rock, which is composed mainly of quartz, lepidolite, albite, K-feldspar, topaz, amblygonite, cassiterite, and columbite. Compared to the topaz-lepidolite granite the aplite and quartz-lepidolite rock shows a number of complementary element enrichments and depletions. The quartz-lepidolite rock is enriched in Fe, Mn, K, Rb, Cs, Li, F, Ba, Sr, Ti, Zr, Nb, W, Th, and Sm. Complementary to this was crystallisation of the strongly peraluminous sodic aplite with the highest tantalum contents measured in this study., The Yichun Ta-Sn-Li deposit occurs within the 9.5-km2 Yashan Igneous Complex, which is made up of felsic, peraluminous intrusions including two-mica, Li-mica, and topaz-lepidolite granites. The topaz-lepidolite granite forms a thin sheet confined to the upper part of the Li-mica granite and is separated from the host metasediments by a marginal pegmatite. The topaz-lepidolite granite is characterised by the presence of snowball textures in which quartz, K-feldspar, and topaz phenocrysts contain albite laths and rare lepidolite and columbite arranged along growth zones. Minor and accessory phases in the topaz-lepidolite granite include amblygonite, cassiterite, columbite-tantalite, microlite, wodginite, zircon, monazite, and pollucite. It is proposed that early crystallisation of the Li-mica granite led to the formation of a Si-poor, Al-, Na-, and flux-rich boundary layer whose low viscosity and density allowed effective separation from the remaining melt and crystals. This melt concentrated incompatible elements including tin and tantalum and accumulated in the upper part of the magma chamber where it crystallised the sheet-like bodies of marginal pegmatite and topaz-lepidolite granite. The uppermost part of the topaz-lepidolite granite consists of aplite and overlying quartz lepidolite rock, which is composed mainly of quartz, lepidolite, albite, K-feldspar, topaz, amblygonite, cassiterite, and columbite. Compared to the topaz-lepidolite granite the aplite and quartz-lepidolite rock shows a number of complementary element enrichments and depletions. The quartz-lepidolite rock is enriched in Fe, Mn, K, Rb, Cs, Li, F, Ba, Sr, Ti, Zr, Nb, W, Th, and Sm. Complementary to this was crystallisation of the strongly peraluminous sodic aplite with the highest tantalum contents measured in this study.

Compared to average crustal abundances, high field strength elements (HFSEs) including Zr, Nb, Hf, Ta, and U are commonly enriched in rare element pegmatites. Albite-spodumene pegmatites may show economic grades of these elements, along with Sn, primarily in oxide minerals. Processes leading to enrichment and precipitation of HFSEs in these rocks are not well understood. Here, the textures and geochemistry of minerals of HFSEs, tin, and base metals in the Leinster albite-spodumene pegmatites are characterised. These data are used to infer processes for enrichment and precipitation of these metals during pegmatite crystallisation, especially subsolidus processes. A detailed paragenetic sequence is presented for the Leinster albite-spodumene pegmatites and it is shown that late-stage aqueous fluids transported HFSEs, especially after all the melt had crystallized. Tantalum enrichment seems to have been controlled by processes affecting the entire crystallising medium, as opposed to fractional crystallisation of columbite-tantalite. Late-stage processes of the type that affected the lithium pegmatites at Leinster may either enhance or reduce economic potential: ore metal tenor may be increased because late-stage columbite-tantalite is generally richer in Ta, and/or ore metals may be lost from pegmatites to country rocks. Lithium pegmatites, including the ones at Leinster, are commonly associated spatially with Sn-W veins and greisen and share some geochemical and textural features, such as evidence of widespread albitisation. It is proposed that lithium pegmatites are transitional products regarding the interrelated dimensions time, temperature, and depth in S-type granite-related Li-Sn-W mineralising systems., Compared to average crustal abundances, high field strength elements (HFSEs) including Zr, Nb, Hf, Ta, and U are commonly enriched in rare element pegmatites. Albite-spodumene pegmatites may show economic grades of these elements, along with Sn, primarily in oxide minerals. Processes leading to enrichment and precipitation of HFSEs in these rocks are not well understood. Here, the textures and geochemistry of minerals of HFSEs, tin, and base metals in the Leinster albite-spodumene pegmatites are characterised. These data are used to infer processes for enrichment and precipitation of these metals during pegmatite crystallisation, especially subsolidus processes. A detailed paragenetic sequence is presented for the Leinster albite-spodumene pegmatites and it is shown that late-stage aqueous fluids transported HFSEs, especially after all the melt had crystallized. Tantalum enrichment seems to have been controlled by processes affecting the entire crystallising medium, as opposed to fractional crystallisation of columbite-tantalite. Late-stage processes of the type that affected the lithium pegmatites at Leinster may either enhance or reduce economic potential: ore metal tenor may be increased because late-stage columbite-tantalite is generally richer in Ta, and/or ore metals may be lost from pegmatites to country rocks. Lithium pegmatites, including the ones at Leinster, are commonly associated spatially with Sn-W veins and greisen and share some geochemical and textural features, such as evidence of widespread albitisation. It is proposed that lithium pegmatites are transitional products regarding the interrelated dimensions time, temperature, and depth in S-type granite-related Li-Sn-W mineralising systems.

The main feature and problem of many of Zimbabwe's intermittent mineral products was the small and erratic nature of their markets and their unpredictable prices. Most of the minor products came from the pegmatite belts in different parts of the country. A range of Li minerals was mined at Bikita, helping the tin mine to stay in production during the 1950s; output included concentrates of lepidolite, amblygonite, eucryptite, petalite and spodumene destined for different industries, lepidolite from the Bikita open pit being used for black-and-whilte television screens and petalite from the Al Hayat orebody for heat-resistant glass and ceramic glazes. Two important Ta minerals were columbite-tantalite and microlite, much in demand by the 1950s for capacitors and widely mined. Wolframite and scheelite, the main W minerals, had a wide distribution in the Bulawayo, Esigodini and Filabusi gold areas as well in pegmatite areas; the RHA mine in the Dete area was reopened and produced its first WO3 concentrate in 2016, using a locally designed plant with a design throughput of 190 000 t/a. Phosphate is found in 8 carbonatite ring complexes, of which Dorowa provided the most important mine, and in 8 bat-guano caves that were worked intermittently. In 2016 Dorowa still had resources of 20 000 000 tonnes at 6.2% P2O5 in the south orebody and 37 000 000 t at 6.8% P2O5 in the unmined north orebody, while the Shawa carbonatite had 10 000 000 t at 10.8% P2O5. Shawa was mined for vermiculite in irregular veins cross-cutting the carbonatites, pyroxenite and syenite, the benched open pit being deep enough in 2016 to become an underground operation soon after. Carbonatites elsewhere frequently host REE, Nb, U, Th, fluorite, barite and occasionally Cu; trenching at Katete carbonatite in 2011 gave 13.2% Ce and 0.6% La with an average of 1.74% REE oxides, subsequent drilling confirming a significant resource. A non-carbonatite resource, the roasting-plant tailings dump in Kwekwe, has 350, The main feature and problem of many of Zimbabwe's intermittent mineral products was the small and erratic nature of their markets and their unpredictable prices. Most of the minor products came from the pegmatite belts in different parts of the country. A range of Li minerals was mined at Bikita, helping the tin mine to stay in production during the 1950s; output included concentrates of lepidolite, amblygonite, eucryptite, petalite and spodumene destined for different industries, lepidolite from the Bikita open pit being used for black-and-whilte television screens and petalite from the Al Hayat orebody for heat-resistant glass and ceramic glazes. Two important Ta minerals were columbite-tantalite and microlite, much in demand by the 1950s for capacitors and widely mined. Wolframite and scheelite, the main W minerals, had a wide distribution in the Bulawayo, Esigodini and Filabusi gold areas as well in pegmatite areas; the RHA mine in the Dete area was reopened and produced its first WO3 concentrate in 2016, using a locally designed plant with a design throughput of 190 000 t/a. Phosphate is found in 8 carbonatite ring complexes, of which Dorowa provided the most important mine, and in 8 bat-guano caves that were worked intermittently. In 2016 Dorowa still had resources of 20 000 000 tonnes at 6.2% P2O5 in the south orebody and 37 000 000 t at 6.8% P2O5 in the unmined north orebody, while the Shawa carbonatite had 10 000 000 t at 10.8% P2O5. Shawa was mined for vermiculite in irregular veins cross-cutting the carbonatites, pyroxenite and syenite, the benched open pit being deep enough in 2016 to become an underground operation soon after. Carbonatites elsewhere frequently host REE, Nb, U, Th, fluorite, barite and occasionally Cu; trenching at Katete carbonatite in 2011 gave 13.2% Ce and 0.6% La with an average of 1.74% REE oxides, subsequent drilling confirming a significant resource. A non-carbonatite resource, the roasting-plant tailings dump in Kwekwe, has 350

The Penouta Sn-Ta deposit, in the northwest of Spain, is a greisenized granitic cupola where Ta minerals occur mainly as disseminations in a leucogranite body intruded in Precambrian–Lower Cambrian gneisses and mica-schists. This leucogranite is a medium- to fine-grained inequigranular rock consisting mainly of quartz, albite, K-feldspar and muscovite. Accessory minerals are mainly of spessartine, zircon, cassiterite, Nb-Ta oxides, monazite, xenotime, native bismuth and pyrite. The alteration processes were mainly albitization, muscovitization and kaolinitization. This leucogranite is peraluminous and P-poor, with 0.03–0.07 wt.% P2O5, 900–1500 ppm Rb, 30–65 ppm Cs, 120–533 ppm Li, 80–140 ppm Ta, 51–81 ppm Nb and up to 569 ppm of Sn. Mineralogical characterization of Nb-Ta oxide minerals was determined by X-ray diffraction, scanning electron microscopy, electron microprobe analysis and mineral liberation analysis. Mn-rich members of the columbite-group minerals (CGM) are the most common Ta-bearing phases, but microlite, wodginite, tapiolite and Ta-rich cassiterite occur also. CGM crystals are commonly zoned concentrically, with a Nb-rich core surrounded by a Ta-rich rim, with a sharp boundary between them. Convoluted zoning occurs also. Dissolution textures resulting from the corrosion of columbite and tantalite rims, in particular, are common. TheMn/(Mn + Fe) ratio varies between 0.33 and 0.97 and the Ta/(Ta + Nb) ratio between 0.07 and 0.93. Wodginite and microlite formed as late replacements of CGM and occur associated with tantalite and cassiterite. Subhedral to anhedral cassiterite crystals, usually up to 200 µmacross, occur in two generations: the earlier one is Nb,Ta-poor whereas in the later generation, the Ta content can reach >9 wt.%of Ta2O5 and 1.7 wt.%of Nb. The presence of a fluid phase in the apical zone of the granite, probably related to the separation of a fluid/vapour of the melt, could explain the sponge-like textures, the Ta enrichment associated, Peer Reviewed, Postprint (published version)

This paper describes the development of analytical methods for the accurate determination of scandium using ICP-OES in both natural scandium-containing and synthetic matrices. Scandium was quantified in different organometallic complexes (form of Sc(acac)3), inorganic salt ScCl3.H2O, Sc2O3, as well as columbite-tantalite ore and tailings from a commercial plant. The organometallic compounds were synthesised from ScCl3.H2O and different acetylacetone liquids as starting materials. Products were purified and characterised by elemental analysis, melting point and IR. Sc recoveries ranging from 75.04(3) to 99.96(4)% were obtained for different organometallic complexes while 99.70(5) and 100.1(5)% recoveries were obtained for ScCl3.H2O and Sc2O3, respectively. Low recoveries obtained for some of the synthesised organometallics were possibly due to the contaminated products and/or incomplete synthesis reactions. Optimum experimental conditions were investigated for the digestion of the ore tailings using NH4F.HF flux. Sc and other elements present in the mineral, namely Nb, Fe, Ti, Al, Mn, Sn, W, Ta, Zr and Y were quantitatively analysed using the newly developed optimum conditions (sample:flux 1:10, 200 degrees C, 60 min., dissolved in water). Sc recovery of ca. 94.23% was obtained., This paper describes the development of analytical methods for the accurate determination of scandium using ICP-OES in both natural scandium-containing and synthetic matrices. Scandium was quantified in different organometallic complexes (form of Sc(acac)3), inorganic salt ScCl3.H2O, Sc2O3, as well as columbite-tantalite ore and tailings from a commercial plant. The organometallic compounds were synthesised from ScCl3.H2O and different acetylacetone liquids as starting materials. Products were purified and characterised by elemental analysis, melting point and IR. Sc recoveries ranging from 75.04(3) to 99.96(4)% were obtained for different organometallic complexes while 99.70(5) and 100.1(5)% recoveries were obtained for ScCl3.H2O and Sc2O3, respectively. Low recoveries obtained for some of the synthesised organometallics were possibly due to the contaminated products and/or incomplete synthesis reactions. Optimum experimental conditions were investigated for the digestion of the ore tailings using NH4F.HF flux. Sc and other elements present in the mineral, namely Nb, Fe, Ti, Al, Mn, Sn, W, Ta, Zr and Y were quantitatively analysed using the newly developed optimum conditions (sample:flux 1:10, 200 degrees C, 60 min., dissolved in water). Sc recovery of ca. 94.23% was obtained.

Peer Reviewed, Postprint (published version)

The effect of fluorine on the solubilities of Mn-columbite (MnNb2O6), Mn-tantalite (MnTa2O6), zircon (ZrSiO4) and hafnon (HfSiO4) were determined in highly fluxed, water-saturated haplogranitic melts at 800 to 1000°C and 2kbar. The melt composition corresponds to the intersection of the granite minimum with the albite-orthoclase tieline (Ab72Or28) in the quartz-albite-orthoclase system (Q-Ab-Or), which is representative of a highly fluxed melt, from which high field strength element minerals may crystallize. The melt contains 1.7wt.% P2O5, 1.05wt.% Li2O and 1.83wt.% B2O3. The main purpose of this study is to examine the effect of F on columbite, tantalite, zircon and hafnon solubility for a melt with this composition. Up to 6wt.% fluorine was added as AgF in order to keep the aluminum saturation index (ASI, molar Al/[Na+K]) of the melt constant. In an additional experiment F was added as AlF3 to make a glass peraluminous. The nominal ASI of the melts are close to 1 for the minimum composition and approximately 1.32 in peraluminous glasses, but if Li is considered as an alkali, the molar ratio Al/[Na+K+Li] of the melts are alkaline (0.87) and subaluminous (1.09), respectively. The molar solubility products [MnO]*[Nb2O5] and [MnO]*[Ta2O5] are nearly independent of the F content of the melt, at approximately 18.19±1.2 and 43.65±2.5×10-4 (mol2/kg2), respectively for the minimum composition. By contrast, there is a positive dependence of zircon and hafnon solubilities on the fluorine content in the minimum composition, which increases from 2.03±0.03×10-4 (mol/kg) ZrO2 and 4.04±0.2×10-4 (mol/kg) HfO2 for melts with 0wt.%F to 3.81±0.3×10-4 (mol/kg) ZrO2 and 6.18±0.04×10-4 (mol/kg) HfO2 for melts with 8wt.%F. Comparison of the data from this work and previous studies indicates that ASI of the melt seems to have a stronger effect than the contents of fluxing elements in the melt and the overall conclusion is that fluorine is less important (relative to melt compositions) tha

Pr3+ ion doped ZnTa2O6, SrTa2O6, CaTa2O6 and ZnTaGaO5 phosphors, which display persistent luminescence were prepared by solid state chemical reaction at 1200 oC for 4 hours. A ZnTa2O6:Pr3+ phosphor that resembled an orthorhombic single phase was obtained, as identified by X-ray diffraction (XRD). ZnTa2O6:Pr3+ displayed both blue and red emission, with the blue emission spectral line observed at 448 nm from the 3P0 → 3H4 transition, and the red spectral lines observed at 608, 619 and 639 nm from the 1D2 → 3H4, 3P0 → 3H6 and 3P0 → 3F2 transitions, respectively. For different concentrations of Pr3+, a concentration of 0.4 mol% Pr3+ proved suitable to generate a phosphor displaying only red emission with the Commission Internationale de l'Eclairage (CIE) coordinates matching those of an ideal red color. Enhancement of the luminescence intensity of ZnTa2O6:Pr3+ phosphor was achieved by preparing it in the presence of Li2SO4 and Li2CO3, which act as flux agents. The strong absorption by the defect levels due to the flux was observed from the diffused reflectance spectra. Pr exists in both Pr3+ and Pr4+ oxidation states as revealed by the X-ray photoelectron spectroscopy data. The presence of Pr3+ increased, while Pr4+ decreased in the samples prepared in the presence of a flux. The increased absorption by the defect levels and the reduction of Pr4+ in the samples prepared using a flux resulted in the enhancement of the luminescence intensity as observed from the photoluminescence spectra. The lifetime of the persistent luminescence of ZnTa2O6:Pr3+ prepared in a flux was calculated using a second order exponential decay curve from the measured phosphorescence decay curves. This showed an enhancement in the lifetime of the persistent luminescence of the fluxed sample, which is attributed to the additional electron trapping centres induced by the flux as observed from the thermoluminescence glow curves. Additional means of enhancing the lifetime of the persistent luminescenc, National Research Foundation (NRF)

The Conflict Minerals legislation is contained in s.1502 of the US Financial Stability Act, otherwise known as the Dodd-Frank Act, and was signed into law in July 2010. The legislation was in response to the ongoing eastern Congolese conflict and its aim is to break the nexus between the mineral proceeds controlled by rebel/non-government troops and the activities of the rebel groups which have been characterised by extreme levels of violence. The commodities covered are cassiterite, columbite-tantalite, gold, wolframite or their derivatives, or any other mineral or their derivatives determined by the Secretary of State to be financing conflict in a covered country, including the Democratic Republic of Congo and its adjoining neighbours, Angola, Burundi, Central African Republic, Republic of Congo, Rwanda, Sudan, Tanzania, Uganda and Zambia. The legislation applies to a US publicly traded company, subject to regulation by the SEC, including certain foreign companies listed on US exchanges. Regulated companies that manufacture products containing 3TG (tin, tantalum, tungsten and gold) are required to show that the 3TG does not originate from a covered country, or if it does that it is conflict free and did not directly or indirectly finance or benefit armed groups in the covered country. While the Act is well-intentioned, the reality is that the legislation does not encompass all minerals from which rebel forces could benefit, implementation of the legislation is ineffective and easily circumvented, the trade in conflict minerals and the eastern Congolese conflict are continuing unabated, the West’s access to 3TG metals as a result of the legislation will be either more restricted and/or more expensive for no reciprocal benefit, some Chinese and other less regulated operators are benefiting from the withdraw of Western operators in relation to access to greater volumes of 3TG metals at cheaper prices, a large number of African artisanal and small scale miners in both, The Conflict Minerals legislation is contained in s.1502 of the US Financial Stability Act, otherwise known as the Dodd-Frank Act, and was signed into law in July 2010. The legislation was in response to the ongoing eastern Congolese conflict and its aim is to break the nexus between the mineral proceeds controlled by rebel/non-government troops and the activities of the rebel groups which have been characterised by extreme levels of violence. The commodities covered are cassiterite, columbite-tantalite, gold, wolframite or their derivatives, or any other mineral or their derivatives determined by the Secretary of State to be financing conflict in a covered country, including the Democratic Republic of Congo and its adjoining neighbours, Angola, Burundi, Central African Republic, Republic of Congo, Rwanda, Sudan, Tanzania, Uganda and Zambia. The legislation applies to a US publicly traded company, subject to regulation by the SEC, including certain foreign companies listed on US exchanges. Regulated companies that manufacture products containing 3TG (tin, tantalum, tungsten and gold) are required to show that the 3TG does not originate from a covered country, or if it does that it is conflict free and did not directly or indirectly finance or benefit armed groups in the covered country. While the Act is well-intentioned, the reality is that the legislation does not encompass all minerals from which rebel forces could benefit, implementation of the legislation is ineffective and easily circumvented, the trade in conflict minerals and the eastern Congolese conflict are continuing unabated, the West’s access to 3TG metals as a result of the legislation will be either more restricted and/or more expensive for no reciprocal benefit, some Chinese and other less regulated operators are benefiting from the withdraw of Western operators in relation to access to greater volumes of 3TG metals at cheaper prices, a large number of African artisanal and small scale miners in both

The politics, conflicts and campaigns associated with the production of columbite-tantalite ore, or coltan as it is known in the Congo, are discussed and the two defining issues analysed: the relationship between coltan and ongoing violence in the Democratic Republic of Congo and the struggle of activists and non-governmental organisations to reshape the global supply chain for tantalum destined for use in mobile phones. The routine assertion that Congo, or at least Central Africa, has 80% of Ta reserves or accounts for 80% of production appears to be unfounded; Central African reserves of tantalite, which in 2010 were estimated to make up 9% of global reserves, are mainly from DR Congo and if half of reported Rwandan production was in fact Congolese then in 2008 the country was the world's second highest producer, accounting for 21% of tantalite output compared with Australia at 30% and Brazil at 14%. There is a strong ethnic dimension to both land ownership and mine organisation; unusually, Ta ore from Congo may be traded half a dozen times along the supply chain before it reaches the established mineral trading companies, which are reluctant to operate in such a dangerous region. The escalating role of minerals in conflicts after the ending of the Cold War is outlined, the many causes of conflict in DR Congo traced and the particular significance of coltan assessed with reference to the major pro-government and anti-government armed groups and their various sources of mineral revenue, which are compared in tables for the periods 1998- 2003 and 2006-2008. Coltan mining is linked to conflict by armed groups profiting from it in four ways: by theft, by direct control of production, by taxing its movement, or by engaging directly in trade/smuggling. The highest estimated profits were US, 1 bib., 1 ind., The politics, conflicts and campaigns associated with the production of columbite-tantalite ore, or coltan as it is known in the Congo, are discussed and the two defining issues analysed: the relationship between coltan and ongoing violence in the Democratic Republic of Congo and the struggle of activists and non-governmental organisations to reshape the global supply chain for tantalum destined for use in mobile phones. The routine assertion that Congo, or at least Central Africa, has 80% of Ta reserves or accounts for 80% of production appears to be unfounded; Central African reserves of tantalite, which in 2010 were estimated to make up 9% of global reserves, are mainly from DR Congo and if half of reported Rwandan production was in fact Congolese then in 2008 the country was the world's second highest producer, accounting for 21% of tantalite output compared with Australia at 30% and Brazil at 14%. There is a strong ethnic dimension to both land ownership and mine organisation; unusually, Ta ore from Congo may be traded half a dozen times along the supply chain before it reaches the established mineral trading companies, which are reluctant to operate in such a dangerous region. The escalating role of minerals in conflicts after the ending of the Cold War is outlined, the many causes of conflict in DR Congo traced and the particular significance of coltan assessed with reference to the major pro-government and anti-government armed groups and their various sources of mineral revenue, which are compared in tables for the periods 1998- 2003 and 2006-2008. Coltan mining is linked to conflict by armed groups profiting from it in four ways: by theft, by direct control of production, by taxing its movement, or by engaging directly in trade/smuggling. The highest estimated profits were US

The main objective of this research was firstly the successful digestion of a series of tantalum containing compounds, with specific exclusion of HF, and secondly, the accurate quantification of tantalum with the help of inductively-coupled plasma optical-emission spectrometry (ICP-OES). The series of tantalum containing compounds include TaF5, TaCl5, Ta2O5, Ta-metal, Ta-CRM (certified reference material), as well as two types of tantalite-ore. The goal of the study of the pentahalide compounds was to verify the use of ICP-OES as analytical method in terms of tantalum recovery. The aqueous dissolution and subsequent quantification of both these compounds was very successful and yielded recovery results of 96 % and 100 % for the fluoride and chloride salts respectively. Validation of the dissolution and quantification of the pentafluoride was within an acceptable range, while the dissolution and quantification methods for the pentachloride was considered exceptionally successful with a recovery of 100.05 % and a t-value = 0.95. Digestion results showed that tantalum pentoxide was considerably more difficult to dissolve than the pentahalides, but good results were eventually obtained after experimentation with various digestion methods. The most successful digestion method was obtained with the help of a high temperature (1100 °C) lithium tetraborate flux, after which the pentoxide melt was dissolved with a mixture of phosphoric acid and methanol. Tantalum recoveries of ca. 97 % were obtained with this method. This study also showed that the CRM and the tantalum metal did not dissolve easily with any of the developed digestion methods. Despite the fact that tantalum is present in the CRM in the form of tantalum pentoxide (0.236 %), the method developed for tantalum pentoxide dissolution did not succeed in completely dissolving the CRM. A qualitative study showed that there are a variety of elements present in the CRM, including Al, Si and Fe, of which especially Al ha

English: Qualitative and quantitative analyses of solid samples using a wet analytical technique, such as ICP-OES, are entirely dependent on the complete dissolution of the samples. Since 1866 niobium and tantalum samples have been successfully dissolved by hydrofluoric acid digestion. However, this method is not preferred in industry due to the dangerous nature of hydrofluoric acid as dissolution reagent. This study was aimed at finding alternative, economically viable and ecologically-friendly conversion methods for the dissolution of Nb metal, Nb2O5, NbF5 and three niobium containing minerals demarcated as Tantalite A, Tantalite B and Sample 1. Acid digestion of Nb and Nb2O5 on a hot plate was investigated with HNO3, HCl, H2SO4, H3PO4 and aqua regia. Both Nb and Nb2O5 dissolved to a greater extent in H2SO4 and H3PO4 (0.94% and 0.36% respectively) than in the other acids but the results were very inaccurate in all the acids. Good recoveries were obtained for NbF5 with recoveries of 95% and 93% from the dissolution of this sample in sulphuric acid and water respectively. Microwave-assisted acid digestion was also investigated with the same acids and high accuracy was obtained with recoveries of 99+% for Nb and Nb2O5 and 100% for NbF5 with H2SO4 digestion. Microwave-assisted digestion of the mineral samples produced 90+% Nb recoveries at digestion periods longer than that for the pure Nb samples. The calibration curves for all the elements showed good linearity as well as high precision (R2 ≥ 0.999) with low y-intercept values which indicated proper background corrections. Flux fusion digestion was investigated with different flux reagents for the dissolution of pure Nb2O5 and the mineral samples. Lithium tetraborate flux produced excellent results for niobium with recoveries of 98.56 to 109.59% Nb2O5 and other major and minor elements. The melt was dissolved in the mixture of H2SO4 and methanol to remove the excess of boron as the B(OMe)3 ester which otherwise resu, Afrikaans: 'n Nat analitiese tegniek soos IGP-OES wat vir die kwantitatiewe en kwalitatiewe analises van vastestof monsters gebruik word, is afhanklik van die algehele oplossing van hierdie monsters. Sedert 1866 is niobium en tantaal monsters suksesvol deur waterstoffluoriedsuur-vertering, opgelos. Aangesien waterstoffluoriedsuur as oplossingmiddel gevaarlik en moeilik hanteerbaar is, word hierdie metode minder geredelik deur maatskappye en navorsers aangewend. Die doel van hierdie studie was om alternatiewe, ekonomies uitvoerbare en omgewingsvriendelike metodes vir die oplossing van niobiummetaal (Nb), niobium(v)oksied (Nb2O5), niobium(v)fluoried (NbF5) sowel as drie niobium bevattende minerale naamlik, "Tantaliet Naquissupa A", "Tantaliet Naquissupa B" en "Monster 1", te vind. Vertering van Nb-metaal en Nb2O5 op warmplaat-verhitting is met die volgende sure ondersoek: HNO3, HCl, H2SO4, H3PO4 en koningswater. Resultate het getoon dat beide Nb-metaal en Nb2O5 beter in H2SO4 en H3PO4 (0.94% en 0.36% onderskeidelik) as in die ander sure oplos, maar die resultate vir al die sure was baie onakkuraat. Goeie herwinnings met hierdie verteringsmetode is vir NbF5 verkry met opbrengste van 95% en 93% in swawelsuur en water onderskeidelik. Mikrogolf-geassisteerde suurverterings was ook met dieselfde sure ondersoek en hoë akkuraatheid met opbrengste van 99+% vir Nb-metaal en Nb2O5 en 100+% vir NbF5 is met H2SO4 vertering verkry. Mikrogolfgeassisteerde vertering van die mineraalmonsters het Nb opbrengste van 90+% vir langer verteringsperiodes gelewer. Die kalibrasie krommes van al die elemente wat ondersoek is, het goeie lineariteit (R2 ≥ 0.999), hoë mate van presisie (% herwinning) en klein y-afsnitte gehad wat op betroubare analitiese resultate dui. Vloeimiddelsmelting is met verskillende smeltmiddels vir die oplossing van suiwer Nb2O5 en ander mineraalmonsters ondersoek. Litiumtertraboraat as smeltmiddel het uitstekende opbrengste vir Nb (98.56 tot 109.59%) sowel as die ander

The processing was investigated of a low grade tantalite-columbite ore formed after the albitisation of granites in Jiangxi, China, and grading 0.013% Ta2O5, 0.021% Nb2O5, 4.97% Na2O, 4.24% K2O, 0.13% LiO2, 0.15% Rb2O, 0.028% Sn and 0.011% ZrO2, using a flowsheet involving leaching, classification, gravity concentration, magnetic separation, flotation and hydrometallurgical processing. A total of 96.5% of the ore was converted into concentrates including tantalite-columbite grading 62.2% (Ta,Nb)2O5, cassiterite grading 62.51% Sn, zinnwaldite grading 1.34% Li2O and 0.40% Rb2O, quartz grading 82% SiO2, feldspar grading 12.06% K2O+Na2O and 19. 67% Al2O3, and topaz., The processing was investigated of a low grade tantalite-columbite ore formed after the albitisation of granites in Jiangxi, China, and grading 0.013% Ta2O5, 0.021% Nb2O5, 4.97% Na2O, 4.24% K2O, 0.13% LiO2, 0.15% Rb2O, 0.028% Sn and 0.011% ZrO2, using a flowsheet involving leaching, classification, gravity concentration, magnetic separation, flotation and hydrometallurgical processing. A total of 96.5% of the ore was converted into concentrates including tantalite-columbite grading 62.2% (Ta,Nb)2O5, cassiterite grading 62.51% Sn, zinnwaldite grading 1.34% Li2O and 0.40% Rb2O, quartz grading 82% SiO2, feldspar grading 12.06% K2O+Na2O and 19. 67% Al2O3, and topaz.

A brief review is presented of legal issues affecting foreign investment in Brazil, Angola and Mozambique. Brazil is the world’s top producer of Nb, the second largest producer of iron ore, a major producer of tantalite, bauxite and Mn and has increasing Cu and Ni production. The country is ranked second behind the Northwest Territories in Canada in relation to the attractive jurisdiction, is the main destination for foreign investment in Latin America and has tax and bilateral investment treaties with a number of countries. Mining and trade in U are subject to a state monopoly and exports are generally not allowed. Angola is not a party to many international treaties or conventions applicable to the mining industry or foreign investments in the sector, but a number of statutes have been published in recent years to promote and expand the mining industry beyond known oil reserves and diamond deposits. Mozambique is a member of the International Centre for Investment Disputes, making it a relatively attractive jurisdiction for mining investment. Projects include the Moatize coal mine, the Moma Ti project and the Mozal Al smelter., A brief review is presented of legal issues affecting foreign investment in Brazil, Angola and Mozambique. Brazil is the world’s top producer of Nb, the second largest producer of iron ore, a major producer of tantalite, bauxite and Mn and has increasing Cu and Ni production. The country is ranked second behind the Northwest Territories in Canada in relation to the attractive jurisdiction, is the main destination for foreign investment in Latin America and has tax and bilateral investment treaties with a number of countries. Mining and trade in U are subject to a state monopoly and exports are generally not allowed. Angola is not a party to many international treaties or conventions applicable to the mining industry or foreign investments in the sector, but a number of statutes have been published in recent years to promote and expand the mining industry beyond known oil reserves and diamond deposits. Mozambique is a member of the International Centre for Investment Disputes, making it a relatively attractive jurisdiction for mining investment. Projects include the Moatize coal mine, the Moma Ti project and the Mozal Al smelter.

The country is highly prospective for Ta and Nb in pegmatites and large granite-related deposits, and the role of the mining and exploration company Mekios Limited in developing the industry is discussed. Columbite-tantalite concentrate production is estimated to be 100 tpa. The minerals are recovered by artisanal miners working mainly alluvial deposits and using simple techniques and equipment. In a typical tin shed, named for their original purpose of recovering Sn, the columbite-tantalite concentrate is sieved to an appropriate grain size and passed through a cross-belt magnetic separator. A roaster may be used to break down the rock into its mineral components without crushing. Mekios intends to support the industry by collecting artisanal concentrates on site and improving their recovery., The country is highly prospective for Ta and Nb in pegmatites and large granite-related deposits, and the role of the mining and exploration company Mekios Limited in developing the industry is discussed. Columbite-tantalite concentrate production is estimated to be 100 tpa. The minerals are recovered by artisanal miners working mainly alluvial deposits and using simple techniques and equipment. In a typical tin shed, named for their original purpose of recovering Sn, the columbite-tantalite concentrate is sieved to an appropriate grain size and passed through a cross-belt magnetic separator. A roaster may be used to break down the rock into its mineral components without crushing. Mekios intends to support the industry by collecting artisanal concentrates on site and improving their recovery.

The geology of the country is described and the mining history and mineral potential are reviewed covering Cu-Co, Au, platinum group metals, iron ore, Al, Nb-tantalite, Sn, W, U, vermiculite, phosphate, aggregates, silica sand, clay, gypsum, salt, limestone and diatomite. Current mining projects include the Tira Au mine, the Kasese Co cathode plant, the Bjordal W mine and the Namekhara vermiculite mine. The new mining act conforms to current international industry conditions and the government began a five-year sustainable management of mineral resources project in 2004., The geology of the country is described and the mining history and mineral potential are reviewed covering Cu-Co, Au, platinum group metals, iron ore, Al, Nb-tantalite, Sn, W, U, vermiculite, phosphate, aggregates, silica sand, clay, gypsum, salt, limestone and diatomite. Current mining projects include the Tira Au mine, the Kasese Co cathode plant, the Bjordal W mine and the Namekhara vermiculite mine. The new mining act conforms to current international industry conditions and the government began a five-year sustainable management of mineral resources project in 2004.

Following the UN initiative to fingerprint the origin of conflict materials, the German Federal Ministry for Economic Cooperation and Development has decided to fund a pilot study on coltan ores. Since 2006, a working group has been investigating columbitetantalite (coltan) mineralisation, also within the wider framework of establishing certified trade chains. More than 300 samples were obtained from the world's major coltan-producing areas. Special attention is directed to samples and concentrates from Ta-Nb-Sn provinces in: Democratic Republic of the Congo, Rwanda, Mozambique, Ethiopia and Namibia. State of the art analytical tools were employed, including fully automated electron microscopy (mineral liberation analysis), electron microprobe analysis (major and minor elements), laser ablation plasma-source mass spectrometry (trace elements and U-Pb dating), X-ray fluorescence spectroscopy (bulk major and trace elements), X-ray diffraction analysis (mineralogy and structure) and thermal-ionisation mass-spectrometry (U-Pb dating). Major and trace element concentration patterns, mineral assemblages in the ore concentrates, age populations (Archaean to early Palaeozoic), and zoning characteristics in the different pegmatites from Africa differ distinctly from each other. Preliminary analytical results indicate that a certification scheme including fingerprinting of sources of coltan ores is feasible., Following the UN initiative to fingerprint the origin of conflict materials, the German Federal Ministry for Economic Cooperation and Development has decided to fund a pilot study on coltan ores. Since 2006, a working group has been investigating columbitetantalite (coltan) mineralisation, also within the wider framework of establishing certified trade chains. More than 300 samples were obtained from the world's major coltan-producing areas. Special attention is directed to samples and concentrates from Ta-Nb-Sn provinces in: Democratic Republic of the Congo, Rwanda, Mozambique, Ethiopia and Namibia. State of the art analytical tools were employed, including fully automated electron microscopy (mineral liberation analysis), electron microprobe analysis (major and minor elements), laser ablation plasma-source mass spectrometry (trace elements and U-Pb dating), X-ray fluorescence spectroscopy (bulk major and trace elements), X-ray diffraction analysis (mineralogy and structure) and thermal-ionisation mass-spectrometry (U-Pb dating). Major and trace element concentration patterns, mineral assemblages in the ore concentrates, age populations (Archaean to early Palaeozoic), and zoning characteristics in the different pegmatites from Africa differ distinctly from each other. Preliminary analytical results indicate that a certification scheme including fingerprinting of sources of coltan ores is feasible.

Forecasts are presented for a range of Australian commodities in a series of 14 brief articles. The significance is discussed of metal price increases and demand from China for the Australian mining industry with particular respect to iron ore, Au and mineral sands. Bauxite production is expected to expand due to the increasing global demand for Al. The development of ionic liquids for Al production is described. The outlook for Cu mining indicates falling revenue to 2011-2012. Gold output is expected to increase to about 320 t in 2011 while iron ore production and exports are forecast to be 360 000 000 and 348 000 000 t, respectively. Figures are presented for revenue growth in Sb, Be, Bi, iron pyrite, Mn, molybdenite, PGMs, tantalite, Sn and W mining, with an expected increase of 1% per annum overall. Mine output of Ni is expected to be up to 50 000 t/y. Demand for Zn is expected to continue to expand while almost all increased Pb mine production will be available for export. Ag prices are expected to ease over the period. Revenue from U mining is forecast to decrease in the absence of new mines and mine expansions., Forecasts are presented for a range of Australian commodities in a series of 14 brief articles. The significance is discussed of metal price increases and demand from China for the Australian mining industry with particular respect to iron ore, Au and mineral sands. Bauxite production is expected to expand due to the increasing global demand for Al. The development of ionic liquids for Al production is described. The outlook for Cu mining indicates falling revenue to 2011-2012. Gold output is expected to increase to about 320 t in 2011 while iron ore production and exports are forecast to be 360 000 000 and 348 000 000 t, respectively. Figures are presented for revenue growth in Sb, Be, Bi, iron pyrite, Mn, molybdenite, PGMs, tantalite, Sn and W mining, with an expected increase of 1% per annum overall. Mine output of Ni is expected to be up to 50 000 t/y. Demand for Zn is expected to continue to expand while almost all increased Pb mine production will be available for export. Ag prices are expected to ease over the period. Revenue from U mining is forecast to decrease in the absence of new mines and mine expansions.

A description is given of the preparation of capacitor-grade Ta powder for both low- and high-voltage applications. The tantalite-columbite ore was treated with HF at high temperature and subjected to liquid-liquid countercurrent solvent extraction using tributyl phosphate with kerosene as solvent. The H2TaF7 obtained was stripped using 1% NaOH and Ta(OH)5 precipitated with NH3 gas. K-salt (K2TaF7) was prepared by dissolving the Ta(OH)5 in HF and neutralising it with KOH. A metallothermic reduction process was used to extract the Ta using liquid Na at above 900 degrees C under Ar. The powder processing of electron-beam-refined Ta through a hydriding/dehydriding process route is described. The product has low oxygen and other impurity contents., A description is given of the preparation of capacitor-grade Ta powder for both low- and high-voltage applications. The tantalite-columbite ore was treated with HF at high temperature and subjected to liquid-liquid countercurrent solvent extraction using tributyl phosphate with kerosene as solvent. The H2TaF7 obtained was stripped using 1% NaOH and Ta(OH)5 precipitated with NH3 gas. K-salt (K2TaF7) was prepared by dissolving the Ta(OH)5 in HF and neutralising it with KOH. A metallothermic reduction process was used to extract the Ta using liquid Na at above 900 degrees C under Ar. The powder processing of electron-beam-refined Ta through a hydriding/dehydriding process route is described. The product has low oxygen and other impurity contents.

The map area is underlain by an assemblage of low- to high-grade metasedimentary rocks, unmetamorphosed platform sediments and an array of granitic, basic and ultrabasic intrusive rocks varying in age from early Mokolian to Namibian. The coast is characterised by extensive Cainozoic deposits. The map area has been of great economic significance for many decades, primarily because of copper mineralisation in the noritoid bodies of the Okiep district and alluvial diamond deposits along the coast and the Buffels River. Other minerals that have been mined in the past include wolframite, scheelite, corundum and pegmatite-related minerals such as feldspar, mica, beryl, bismuth, tantalite-columbite and lithium-bearing minerals. Uranium associated with leucogranite bodies was discovered on Nooitgedacht and there is diatomaceous earth at Kannikwa 156., The map area is underlain by an assemblage of low- to high-grade metasedimentary rocks, unmetamorphosed platform sediments and an array of granitic, basic and ultrabasic intrusive rocks varying in age from early Mokolian to Namibian. The coast is characterised by extensive Cainozoic deposits. The map area has been of great economic significance for many decades, primarily because of copper mineralisation in the noritoid bodies of the Okiep district and alluvial diamond deposits along the coast and the Buffels River. Other minerals that have been mined in the past include wolframite, scheelite, corundum and pegmatite-related minerals such as feldspar, mica, beryl, bismuth, tantalite-columbite and lithium-bearing minerals. Uranium associated with leucogranite bodies was discovered on Nooitgedacht and there is diatomaceous earth at Kannikwa 156.

Karnataka forms part of the mineral-rich Archaean Indian Shield and, for its size, is fairly well endowed with a wide variety of minerals. It is India's major producer of primary gold and has considerable resources of iron, manganese and chromium. Its aluminium, copper, lead and zinc, though not abundant, can meet Karnataka's requirements. There is a good variety of industrial minerals such as asbestos, bauxite, corundum, dolomite, limestone, lime, fireclay, kaolin, kyanite, magnesite, ochre, pyrite, quartz, scheelite, soapstone and heavy mineral sand. Ornamental building stones include granite, whose quarrying, cutting and polishing has recently grown considerably. The greatest deficiency is in fuel resources. The state's mining history, production and ore genesis are summarised and its mineral deposits are described in reports on 55 commodities., Karnataka forms part of the mineral-rich Archaean Indian Shield and, for its size, is fairly well endowed with a wide variety of minerals. It is India's major producer of primary gold and has considerable resources of iron, manganese and chromium. Its aluminium, copper, lead and zinc, though not abundant, can meet Karnataka's requirements. There is a good variety of industrial minerals such as asbestos, bauxite, corundum, dolomite, limestone, lime, fireclay, kaolin, kyanite, magnesite, ochre, pyrite, quartz, scheelite, soapstone and heavy mineral sand. Ornamental building stones include granite, whose quarrying, cutting and polishing has recently grown considerably. The greatest deficiency is in fuel resources. The state's mining history, production and ore genesis are summarised and its mineral deposits are described in reports on 55 commodities.

Mineral deposits in the two sheet areas are described. Economically important deposits occur in rocks of the Swazian Erathem, the Bushveld Complex, the Phalaborwa Complex and the Karoo Supergroup. The Swazian Erathem contains deposits of gold, antimony, zinc, copper, emeralds, scheelite, mercury and vanadiferous titanomagnetite in the greenstone belts; corundum, beryl, columbite-tantalite and molybdenum in pegmatites; and silica in quartz veins. The Bushveld Complex contains platinum group elements, nickel and copper in the Platreef, vanadiferous titanomagnetite in the Main Magnetite Seam and the Bobbejaankop Granite dimension stone. The Phalaborwa Complex contains large reserves of copper, magnetite, precious metals, uranium, zirconium, nickel, apatite and vermiculite. The Schiel Complex contains apatite, magnetite, copper and vermiculite. Lead, barite and silver occur in Archaean rocks adjacent to the Proterozoic Blouberg Graben. Substantial reserves of economically viable coal occur in outliers of Karoo rocks in the Beerkraal and Tolwe areas. Appendices list commodity and locality data for all minerals (except coal) and operating mining enterprises sorted by map number., Mineral deposits in the two sheet areas are described. Economically important deposits occur in rocks of the Swazian Erathem, the Bushveld Complex, the Phalaborwa Complex and the Karoo Supergroup. The Swazian Erathem contains deposits of gold, antimony, zinc, copper, emeralds, scheelite, mercury and vanadiferous titanomagnetite in the greenstone belts; corundum, beryl, columbite-tantalite and molybdenum in pegmatites; and silica in quartz veins. The Bushveld Complex contains platinum group elements, nickel and copper in the Platreef, vanadiferous titanomagnetite in the Main Magnetite Seam and the Bobbejaankop Granite dimension stone. The Phalaborwa Complex contains large reserves of copper, magnetite, precious metals, uranium, zirconium, nickel, apatite and vermiculite. The Schiel Complex contains apatite, magnetite, copper and vermiculite. Lead, barite and silver occur in Archaean rocks adjacent to the Proterozoic Blouberg Graben. Substantial reserves of economically viable coal occur in outliers of Karoo rocks in the Beerkraal and Tolwe areas. Appendices list commodity and locality data for all minerals (except coal) and operating mining enterprises sorted by map number.

Ivory Coast is dominated by Archaean to Lower Proterozoic rocks with 2% of Cretaceous to Recent sedimentary basin. Birimian rocks host gold in veins, lensoid reefs and argillites, manganese, diamonds, nickel and cobalt, banded iron formations, tin, tantalite, rutile and some industrial minerals, while eluvial gold is mined at Ity and Aniuri. Offshore oil and natural gas are also being developed. Geological mapping at 1:200 000 is in progress and larger-scale aeromagnetic and aeroelectromagnetic maps are available for many areas. A new mining code is to include a 3% ad valorem tax on gold, no export taxes on metals, a 10% state equity share in new mines, a 7 year exploration phase with one renewal, and more security of tenure in the transfer to exploitation. The Societe Nationale de Developpement Minier, Sodemi, aims to form partnerships for feasibility study and development of known deposits., Ivory Coast is dominated by Archaean to Lower Proterozoic rocks with 2% of Cretaceous to Recent sedimentary basin. Birimian rocks host gold in veins, lensoid reefs and argillites, manganese, diamonds, nickel and cobalt, banded iron formations, tin, tantalite, rutile and some industrial minerals, while eluvial gold is mined at Ity and Aniuri. Offshore oil and natural gas are also being developed. Geological mapping at 1:200 000 is in progress and larger-scale aeromagnetic and aeroelectromagnetic maps are available for many areas. A new mining code is to include a 3% ad valorem tax on gold, no export taxes on metals, a 10% state equity share in new mines, a 7 year exploration phase with one renewal, and more security of tenure in the transfer to exploitation. The Societe Nationale de Developpement Minier, Sodemi, aims to form partnerships for feasibility study and development of known deposits.

Brazil is one of the world's most important pegmatite mineral producers, contributing beryl, tantalite, columbite, micas, feldspar, clays, lithium and uranium minerals and a large variety of gemstones. There are four distinct, widely distributed pegmatite provinces: Borborema, Oriental, Goias and Para-Amazon. There are three types of pegmatites: homogeneous, heterogeneous and mixed. The granitic pegmatite mineralogy is very versatile and there are around 100 species of phosphates, Nb-Ta oxides and gemstones. Many new minerals have been discovered from Brazilian pegmatites. The minerals produced are coveted for jewellery and as collection pieces in museums. Various mineralogical data is presented for some of the rare and important minerals. Pegmatite industrial minerals are produced and marketed in large quantities. The niobate-tanatalates, beryls, gemstones and crystal aggregates are produced in lesser quantities but are of greater significance. Production and reserves figures are provided for beryl, feldpsar, lithium, tantalite, rare earths, mica and gems. The problems of pegmatite small mining are outlined., Brazil is one of the world's most important pegmatite mineral producers, contributing beryl, tantalite, columbite, micas, feldspar, clays, lithium and uranium minerals and a large variety of gemstones. There are four distinct, widely distributed pegmatite provinces: Borborema, Oriental, Goias and Para-Amazon. There are three types of pegmatites: homogeneous, heterogeneous and mixed. The granitic pegmatite mineralogy is very versatile and there are around 100 species of phosphates, Nb-Ta oxides and gemstones. Many new minerals have been discovered from Brazilian pegmatites. The minerals produced are coveted for jewellery and as collection pieces in museums. Various mineralogical data is presented for some of the rare and important minerals. Pegmatite industrial minerals are produced and marketed in large quantities. The niobate-tanatalates, beryls, gemstones and crystal aggregates are produced in lesser quantities but are of greater significance. Production and reserves figures are provided for beryl, feldpsar, lithium, tantalite, rare earths, mica and gems. The problems of pegmatite small mining are outlined.

Aspects of beneficiation considered in the 16 papers include: applied mineralogy of alluvial tin; alluvial tailings; improved spiral technology; dry separation; energy consumption and transport and processing costs in Malaysian gravel pump mines; ore treatment at P.T. Koba Tin; beneficiation at Bidor Malaya Tin; gravity concentrating trays; by-product recovery; separation of columbite-tantalite from ilmenite; tin liberation from limonitic boulders; heavy medium cyclones; Bolivian treatment practices; tungsten recovery by caustic leaching; arsenic removal from roaster dust; and pyrometallurgy and hydrometallurgy of tin-tantalum-antimony at Greenbushes, Australia. Discussions of each paper, and the panel discussion, are also included., Aspects of beneficiation considered in the 16 papers include: applied mineralogy of alluvial tin; alluvial tailings; improved spiral technology; dry separation; energy consumption and transport and processing costs in Malaysian gravel pump mines; ore treatment at P.T. Koba Tin; beneficiation at Bidor Malaya Tin; gravity concentrating trays; by-product recovery; separation of columbite-tantalite from ilmenite; tin liberation from limonitic boulders; heavy medium cyclones; Bolivian treatment practices; tungsten recovery by caustic leaching; arsenic removal from roaster dust; and pyrometallurgy and hydrometallurgy of tin-tantalum-antimony at Greenbushes, Australia. Discussions of each paper, and the panel discussion, are also included.

The incidence of tin mineralisation in the lepidolite- bearing pegmatites of Govindpal was discovered in 1973. The cassiterite and the association columbite and tantalite mineralisation found in the pegmatites grades from 0.1-0.3% cassiterite in some areas and 0.5-1% in others. Geochemical analyses were carried out on samples by emission spectrometry and atomic absorption spectrometry. Samples from preliminary mineral processing test s were analysed using x-ray fluorescence., The incidence of tin mineralisation in the lepidolite- bearing pegmatites of Govindpal was discovered in 1973. The cassiterite and the association columbite and tantalite mineralisation found in the pegmatites grades from 0.1-0.3% cassiterite in some areas and 0.5-1% in others. Geochemical analyses were carried out on samples by emission spectrometry and atomic absorption spectrometry. Samples from preliminary mineral processing test s were analysed using x-ray fluorescence.

Sulphuric acid increases the extraction of tantalum from tantalite concentrates when using hydrofluoric acid. The maximum extraction of Ta from tantalite using HF was about 50%, but adding 35% H2SO4 increased extraction to 95% at 60 degrees C. When leaching tantalite with a mixture of HF/H2SO4, higher temperatures and H2SO4 concentrations are needed for good extractions. Lowering either reduces extraction dramatically., Sulphuric acid increases the extraction of tantalum from tantalite concentrates when using hydrofluoric acid. The maximum extraction of Ta from tantalite using HF was about 50%, but adding 35% H2SO4 increased extraction to 95% at 60 degrees C. When leaching tantalite with a mixture of HF/H2SO4, higher temperatures and H2SO4 concentrations are needed for good extractions. Lowering either reduces extraction dramatically.

Vacuum flotation experiments have indicated that these acids have potential as collectors for the selective flotation of minerals. 22 minerals were tested over a wide pH range, with the collectors' chain lengths varying from n-propyl (3 carbon) to dodecyl (12 carbon). The flotation response varied in both the chain length required to promote flotation and in the pH sensitivity of the position of the incipient flotation areas., Vacuum flotation experiments have indicated that these acids have potential as collectors for the selective flotation of minerals. 22 minerals were tested over a wide pH range, with the collectors' chain lengths varying from n-propyl (3 carbon) to dodecyl (12 carbon). The flotation response varied in both the chain length required to promote flotation and in the pH sensitivity of the position of the incipient flotation areas.

[ES] En el sector Tirados de la Vega-Golpejas han sido detectadas dos anomalías de casiterita en los aluviones del Regato de los Lentiscos y en otros existentes al sur de Tirados de la Vega. El estudio granométrico y morfométrico de éstas casiteritas. contrastado con el de la casiterita procedente del granito de Golpejas. permite asegurar que la anomalía del Regato de los Lentiscos se debe a la dispersión de la casiterita de aquel granito. mientras que la de Tirados de la Vega procede de filones estanníferos. La aplicación del análisis factoral corrobora este hecho y permite diferenciar las casiteritas que proceden de rocas graníticas de aquellas que vienen de filones estanníferos. Según esto se puede indicar que la capacidad de migración de la casiterita desde el yacimiento estannífero de Golpejas es de unos 3 Kms., [EN] Two cassiterite anomalies have been detected in the Regato de los Lentisco and Tirados de la Vega alluviums, in the Golpejas area (Salamanca). The granometric and morphometric parameters of these cassiterites have been compared with those shown by the cassiterite crystal ocurrying in the Golpejas granite. The comparison between the two groups of data allow us to conclude that the anomaly observed in the Regato de los Lentistos has been originated by the disperssion of the cassiterite from the primary deposit of Golpejas. On the contrary, the anomaly ocurring in the alloviums to the south of Tirados de la Vega shows a different origin, and is coming from stanniferous veins. The factor anylisis corroborates the differentiation mentionated above, and indicates a migration capacite of about 3 kms. from the stannifeous deposits of Golpejas for the alluvial cassiterite.

The mineralised zone is in the Sinnamary river valley. Notes on prospecting and exploration are given., The mineralised zone is in the Sinnamary river valley. Notes on prospecting and exploration are given.

Political and economic reforms in the country have resulted in major investments in the mining, minerals and energy sectors. Noventa has secured the rights to key tantalite deposits and the Marropino mine has been re-developed while the nearby Marrua mine is currently being developed. A drilling programme is underway to identify reserves and ore characteristics in the other concessions and the establishment of a centralised finishing plant is being pursued to upgrade the concentrates from the mines., Political and economic reforms in the country have resulted in major investments in the mining, minerals and energy sectors. Noventa has secured the rights to key tantalite deposits and the Marropino mine has been re-developed while the nearby Marrua mine is currently being developed. A drilling programme is underway to identify reserves and ore characteristics in the other concessions and the establishment of a centralised finishing plant is being pursued to upgrade the concentrates from the mines.

The closure of Uis tin mine in Namibia left the local community with severe problems. Legal, safe and economically sustainable small-scale mining might be one alternative for the future, creating 100-150 jobs and producing 15-20 tons/a of Sn/Ta concentrates. A pilot project has shown that small-scale pegmatite mining is economically feasible but that the profitability is marginal. Tin and tantalite must be extracted in parallel. Although mechanisation is necessary and can be supported by local resources, preconcentration should be manual. Organisation and training are key elements for the project and are very time-consuming. Buyers for tin are available; competition between buyers gives much better prices. Environmental problems are small and manageable. The business environment needs improvement and the small miners need their own organisation, as well as support in geology, engineering and marketing., The closure of Uis tin mine in Namibia left the local community with severe problems. Legal, safe and economically sustainable small-scale mining might be one alternative for the future, creating 100-150 jobs and producing 15-20 tons/a of Sn/Ta concentrates. A pilot project has shown that small-scale pegmatite mining is economically feasible but that the profitability is marginal. Tin and tantalite must be extracted in parallel. Although mechanisation is necessary and can be supported by local resources, preconcentration should be manual. Organisation and training are key elements for the project and are very time-consuming. Buyers for tin are available; competition between buyers gives much better prices. Environmental problems are small and manageable. The business environment needs improvement and the small miners need their own organisation, as well as support in geology, engineering and marketing.

Relief shown by contours and shading. Includes 1 cross section: "horizontal scale 1"= 1.014 miles; vertical 1"=500 feet." Accompanying pamphlet: "Geology of 1/4° field sheet no. 32" (vi, 66 p. ; 26 cm.). Prospecting activity in this area, at one time extensive, has now ceased and there is not considered to be any justification in encouraging renewed prospecting. The following minerals have been noted: tin, gold, platinum, molybdenum, columbite, tantalite and several radioactive minerals, wofram and scheelite, silver, arsenic and manganese., bib., Relief shown by contours and shading. Includes 1 cross section: "horizontal scale 1"= 1.014 miles; vertical 1"=500 feet." Accompanying pamphlet: "Geology of 1/4° field sheet no. 32" (vi, 66 p. ; 26 cm.). Prospecting activity in this area, at one time extensive, has now ceased and there is not considered to be any justification in encouraging renewed prospecting. The following minerals have been noted: tin, gold, platinum, molybdenum, columbite, tantalite and several radioactive minerals, wofram and scheelite, silver, arsenic and manganese.

Columbite is widely distributed in the alluvial tin deposits of N. Nigeria and most of the ore is won as a by-product of the tin mining industry. The physical and chemical properties of columbite-tantilite are described, its detection by ultra violet light and occurrences. There are notes on preparation and tables of produce by provinces., bib., Columbite is widely distributed in the alluvial tin deposits of N. Nigeria and most of the ore is won as a by-product of the tin mining industry. The physical and chemical properties of columbite-tantilite are described, its detection by ultra violet light and occurrences. There are notes on preparation and tables of produce by provinces.

Artisinal production at the Musha and Ntunga concessions has mainly been of cassiterite and tantalite. Historical production from colonial era operations and artisanal miners is estimated at +20,000 t Sn. Shallow underground mining at Musha is based on vein deposits hosting coarse-grained cassiterite whereas Ntunga is from narrower than 1 m to wider than 30 m highly kaolinised Sn-Ta pegmatites, although high-grade Sn has also been produced from a quartz-mica stockwork. Drilling has shown that the two areas, although 4 km apart, have similar lithologies and mineralisation at depth. There appears to be overall vertical zoning from massive pegmatite through high-grade Sn-quartz veins with thin pegmatites to shallower mineralised quartz-mica veins. The pegmatites are variable in style and zoned; grades range up to 700 ppm Ta and above 10% Sn. High-grade drill vein Sn intersections in 2018 include 4 m at 4.0% Sn and 1.9 m at 7.4% Sn. Deep drilling has intersected spodumene below 150 m with several intersections greater than 50 m at over 1% Li2O. QEMSCAN and XRD analyses indicate spodumene as the dominant mineral with minor probable Li mica as well as petalite and ambylgonite in a quartz albite matrix. An overall model is proposed in which fractionated Li-rich pegmatites precipitated disseminated Sn-Ta mineralisation but much of the Sn was precipitated in high-grade zones where magmatic fluids mixed with metamorphic fluids from interbedded pelites and psammites. The upper 100 m of the deposit is very similar to the style of mineralisation found at the major Rutongo deposit in Rwanda but dissimilar to the major Bisie discovery in the Democratic Republic of Congo and tin deposits in Cornwall. The mineralisation below 150 m shows characteristics of classic lithium-caesium-tantalum (LCT) family pegmatites together with enriched high-grade Sn zones which are unlike any known deposit., Artisinal production at the Musha and Ntunga concessions has mainly been of cassiterite and tantalite. Historical production from colonial era operations and artisanal miners is estimated at +20,000 t Sn. Shallow underground mining at Musha is based on vein deposits hosting coarse-grained cassiterite whereas Ntunga is from narrower than 1 m to wider than 30 m highly kaolinised Sn-Ta pegmatites, although high-grade Sn has also been produced from a quartz-mica stockwork. Drilling has shown that the two areas, although 4 km apart, have similar lithologies and mineralisation at depth. There appears to be overall vertical zoning from massive pegmatite through high-grade Sn-quartz veins with thin pegmatites to shallower mineralised quartz-mica veins. The pegmatites are variable in style and zoned; grades range up to 700 ppm Ta and above 10% Sn. High-grade drill vein Sn intersections in 2018 include 4 m at 4.0% Sn and 1.9 m at 7.4% Sn. Deep drilling has intersected spodumene below 150 m with several intersections greater than 50 m at over 1% Li2O. QEMSCAN and XRD analyses indicate spodumene as the dominant mineral with minor probable Li mica as well as petalite and ambylgonite in a quartz albite matrix. An overall model is proposed in which fractionated Li-rich pegmatites precipitated disseminated Sn-Ta mineralisation but much of the Sn was precipitated in high-grade zones where magmatic fluids mixed with metamorphic fluids from interbedded pelites and psammites. The upper 100 m of the deposit is very similar to the style of mineralisation found at the major Rutongo deposit in Rwanda but dissimilar to the major Bisie discovery in the Democratic Republic of Congo and tin deposits in Cornwall. The mineralisation below 150 m shows characteristics of classic lithium-caesium-tantalum (LCT) family pegmatites together with enriched high-grade Sn zones which are unlike any known deposit.

Interviews and photographs are used to illustrate how female-led artisanal mining associations are fighting against exploitation and cultural barriers to their equal participation in a predominantly male mining industry in the Democratic Republic of Congo. Particular reference is to a woman who is not only a cassiterite, columbite and tantalite mineral trader but also a pit owner and member of a mining cooperative in Masisi, North Kivu, and to the gold mining area around Kamituga in South Kivu where ALEFEM, the Association to Fight Against the Exploitation of Women and Children in the Mining Sector, was founded in 2006. Specific issues such as the sexual exploitation and health problems associated with manual quartz crushing at the gold mines are highlighted but the emphasis is on how mining associations contribute to women's social emancipation by boosting their self-determination., Interviews and photographs are used to illustrate how female-led artisanal mining associations are fighting against exploitation and cultural barriers to their equal participation in a predominantly male mining industry in the Democratic Republic of Congo. Particular reference is to a woman who is not only a cassiterite, columbite and tantalite mineral trader but also a pit owner and member of a mining cooperative in Masisi, North Kivu, and to the gold mining area around Kamituga in South Kivu where ALEFEM, the Association to Fight Against the Exploitation of Women and Children in the Mining Sector, was founded in 2006. Specific issues such as the sexual exploitation and health problems associated with manual quartz crushing at the gold mines are highlighted but the emphasis is on how mining associations contribute to women's social emancipation by boosting their self-determination.

The leaching and solvent extraction behavior of uranium and thorium from a high-grade Ethiopian tantalite pegmatite ore in a mixture of hydrofluoric acid and sulphuric acid has been investigated. The effects of variables such as temperature, particle size, acid concentration, and leaching time were studied. The leaching efficiency of uranium increased with increasing temperature to 150 degrees C, at which 96% removal of uranium was achieved. Particles in the size range of -100 to +75 micrometres resulted in the highest leaching of uranium, while formation of a colloidal suspension was observed when using a fine particle size fraction (-75 micrometres). The dissolution of uranium increased with increasing leaching time. No significant systematic dependence of the leachability of thorium on the above variables was observed. Optimum extraction of uranium and thorium using D2EHPA was obtained when using aqueous/organic phase volume ratio of 1:1, solvent concentration of 0.3 M, and contact time of 20 min. (Authors.), The leaching and solvent extraction behavior of uranium and thorium from a high-grade Ethiopian tantalite pegmatite ore in a mixture of hydrofluoric acid and sulphuric acid has been investigated. The effects of variables such as temperature, particle size, acid concentration, and leaching time were studied. The leaching efficiency of uranium increased with increasing temperature to 150 degrees C, at which 96% removal of uranium was achieved. Particles in the size range of -100 to +75 micrometres resulted in the highest leaching of uranium, while formation of a colloidal suspension was observed when using a fine particle size fraction (-75 micrometres). The dissolution of uranium increased with increasing leaching time. No significant systematic dependence of the leachability of thorium on the above variables was observed. Optimum extraction of uranium and thorium using D2EHPA was obtained when using aqueous/organic phase volume ratio of 1:1, solvent concentration of 0.3 M, and contact time of 20 min. (Authors.)

Ta-Nb oxides in the Yichun deposit occur disseminated in a topaz lepidolite granite and in the intermediate zone of a zoned marginal pegmatite. Columbite-group minerals and microlite are the principal ore minerals in this topaz lepidolite granite. The principal Ta-Nb oxides in aplite of the marginal pegmatite are columbite-(Mn), tantalite-(Mn), and wodginite-group minerals. Ta-Nb oxides in the topaz lepidolite granite and aplite are mostly prismatic crystals or aggregates associated with lepidolite and albite, whereas in the pegmatitic intermediate zone, they occur in triplite-dominated nodules as aggregates of acicular columbite-(Mn) in association with fibrous molybdenite, zircon, and native bismuth. Most columbite-group minerals in the topaz lepidolite granite and aplite have a columbite-(Mn) core (stage I), overgrown and resorbed by a later stage II columbite-group mineral overgrowth that is distinctly richer in Ta than the stage I crystals. Stage I crystals enclosed by snowball quartz are richer in Nb, Sc, Fe, Ti, Y, Zr, U, Th, and W, and thus are more primitive in composition than those outside the snowball quartz. Textural and chemical features of the stage I crystals are consistent with a magmatic origin. The chemistry of columbite-group minerals, as well as the published chronological data, suggest that aplite was not derived directly from the topaz lepidolite granite melt; rather, it represents a different magma that originated from the same magma chamber at depth from which the topaz lepidolite granite melt was derived., Ta-Nb oxides in the Yichun deposit occur disseminated in a topaz lepidolite granite and in the intermediate zone of a zoned marginal pegmatite. Columbite-group minerals and microlite are the principal ore minerals in this topaz lepidolite granite. The principal Ta-Nb oxides in aplite of the marginal pegmatite are columbite-(Mn), tantalite-(Mn), and wodginite-group minerals. Ta-Nb oxides in the topaz lepidolite granite and aplite are mostly prismatic crystals or aggregates associated with lepidolite and albite, whereas in the pegmatitic intermediate zone, they occur in triplite-dominated nodules as aggregates of acicular columbite-(Mn) in association with fibrous molybdenite, zircon, and native bismuth. Most columbite-group minerals in the topaz lepidolite granite and aplite have a columbite-(Mn) core (stage I), overgrown and resorbed by a later stage II columbite-group mineral overgrowth that is distinctly richer in Ta than the stage I crystals. Stage I crystals enclosed by snowball quartz are richer in Nb, Sc, Fe, Ti, Y, Zr, U, Th, and W, and thus are more primitive in composition than those outside the snowball quartz. Textural and chemical features of the stage I crystals are consistent with a magmatic origin. The chemistry of columbite-group minerals, as well as the published chronological data, suggest that aplite was not derived directly from the topaz lepidolite granite melt; rather, it represents a different magma that originated from the same magma chamber at depth from which the topaz lepidolite granite melt was derived.

Bulk (800-1 400 kg) samples were taken from run-of-mine material from each of three representative Rwandan artisanal and small-scale mining operations, Mine 1 producing a cassiterite concentrate and Mine 2 a mixed cassiterite and tantalite (coltan) concentrate - both from pegmatite-hosted ores - and Mine 3 producing a wolframite concentrate from quartz veins. The target minerals for Mines 1-3 were found to be principally distributed in the medium and coarse, fine, and very coarse grain-size fractions, respectively, of run-of-mine material. A sub-sample from each mine was subjected to traditional artisanal-processing tests using density sorting applied in washing pans and ground sluices, and the other three sub-samples underwent basic mechanical-processing tests (shaking tables, spiral concentrator and magnetic separator) at Phoenix Metal's Kigali plant. The results showed that the mechanical and artisanal processing of the pegmatite-hosted cassiterite ore from Mine 1 achieved the highest recovery rates (72.84 and 60.10%, respectively), while the tests performed for Mines 2 and 3 provided lower recovery rates that were in the range 10.97-26.02%. Artisanal processing for Mine 2 was observed to be more efficient than mechanical processing, in contrast to Mines 1 and 3. The results of model economic calculations indicated that, in terms of profitability, mechanical processing was superior to artisanal processing for Mine 1, while the reverse was the case for Mine 2, and Mine 3 displayed an apparent lack of profitability for both processes., Bulk (800-1 400 kg) samples were taken from run-of-mine material from each of three representative Rwandan artisanal and small-scale mining operations, Mine 1 producing a cassiterite concentrate and Mine 2 a mixed cassiterite and tantalite (coltan) concentrate - both from pegmatite-hosted ores - and Mine 3 producing a wolframite concentrate from quartz veins. The target minerals for Mines 1-3 were found to be principally distributed in the medium and coarse, fine, and very coarse grain-size fractions, respectively, of run-of-mine material. A sub-sample from each mine was subjected to traditional artisanal-processing tests using density sorting applied in washing pans and ground sluices, and the other three sub-samples underwent basic mechanical-processing tests (shaking tables, spiral concentrator and magnetic separator) at Phoenix Metal's Kigali plant. The results showed that the mechanical and artisanal processing of the pegmatite-hosted cassiterite ore from Mine 1 achieved the highest recovery rates (72.84 and 60.10%, respectively), while the tests performed for Mines 2 and 3 provided lower recovery rates that were in the range 10.97-26.02%. Artisanal processing for Mine 2 was observed to be more efficient than mechanical processing, in contrast to Mines 1 and 3. The results of model economic calculations indicated that, in terms of profitability, mechanical processing was superior to artisanal processing for Mine 1, while the reverse was the case for Mine 2, and Mine 3 displayed an apparent lack of profitability for both processes.

Tantalum is an important metal for high-technology applications. It is recovered from oxide minerals present as minor constituents in rare-metal granites (RMG) and granitic rare-element pegmatites (REP). Significant potential exists as a by-product of spodumene mining from pegmatites, and from Nb-Zr-rare earth element (REE) mining from carbonatites and peralkaline igneous rocks. Columbite-group minerals (CGM) account for the majority of the current Ta production. The estimated Ta resources of Africa are more than 50 000 tons of contained Ta2O5, representing 16% of the world resources. Currently, the economically most important mining districts in Africa are located within the Kibara Belt (mainly Rwanda and the DR Congo), around the Kenticha mine (Ethiopia) and in the Alto Ligonha Province (Mozambique). Production from pegmatites and related placer deposits is mostly from hundreds of artisanal and small-scale workings with only a handful of semi-industrial Ta mines. Collectively, African operations are currently responsible for more than half of the world’s primary Ta. Each period of Ta ore formation is characterised by specific mineralogical and geochemical features. Compositions of CGM are variable, from Fe-rich types to Mn-rich columbite-tantalite. Trace element concentrations in CGM and other Ta-Nb oxides are highly variable, with Ti, W, Sn, Zr, Hf, Y, Sc and REE displaying significant regional differences that may be used to discriminate Ta provinces., Tantalum is an important metal for high-technology applications. It is recovered from oxide minerals present as minor constituents in rare-metal granites (RMG) and granitic rare-element pegmatites (REP). Significant potential exists as a by-product of spodumene mining from pegmatites, and from Nb-Zr-rare earth element (REE) mining from carbonatites and peralkaline igneous rocks. Columbite-group minerals (CGM) account for the majority of the current Ta production. The estimated Ta resources of Africa are more than 50 000 tons of contained Ta2O5, representing 16% of the world resources. Currently, the economically most important mining districts in Africa are located within the Kibara Belt (mainly Rwanda and the DR Congo), around the Kenticha mine (Ethiopia) and in the Alto Ligonha Province (Mozambique). Production from pegmatites and related placer deposits is mostly from hundreds of artisanal and small-scale workings with only a handful of semi-industrial Ta mines. Collectively, African operations are currently responsible for more than half of the world’s primary Ta. Each period of Ta ore formation is characterised by specific mineralogical and geochemical features. Compositions of CGM are variable, from Fe-rich types to Mn-rich columbite-tantalite. Trace element concentrations in CGM and other Ta-Nb oxides are highly variable, with Ti, W, Sn, Zr, Hf, Y, Sc and REE displaying significant regional differences that may be used to discriminate Ta provinces.

The area lies in the province of Nuflo de Chavez. Detailed topographic and geological maps of La Verde mine and Palmira mine were constructed, which assisted in the planning of pitting operations over the two pegmatites. Kaolin samples were collected by channel-sampling the adits and the pit walls in both locations. 22 other pegmatites were located and mapped, and samples of mica, feldspar, kaolin and country rock were collected from several of the bodies. Location, working, geology and economic potential of each pegmatite is discussed., The area lies in the province of Nuflo de Chavez. Detailed topographic and geological maps of La Verde mine and Palmira mine were constructed, which assisted in the planning of pitting operations over the two pegmatites. Kaolin samples were collected by channel-sampling the adits and the pit walls in both locations. 22 other pegmatites were located and mapped, and samples of mica, feldspar, kaolin and country rock were collected from several of the bodies. Location, working, geology and economic potential of each pegmatite is discussed.

Reflected light microscope and electron microprobe studies on panning concentrates from selected eluvial and stream niobium-tantalum-tin deposits of the Omkoi area indicate that the Nb-Ta minerals associated with cassiterite are columbite-tantalite, Nb-Ta rutile, with some tapiolite and samarskite. Cassiterite, columbite-tantalite and Nb-Ta rutile occur mainly as free particles and thus gravity separation can be used in the first stage, followed by magnetic and electrostatic separation techniques., Reflected light microscope and electron microprobe studies on panning concentrates from selected eluvial and stream niobium-tantalum-tin deposits of the Omkoi area indicate that the Nb-Ta minerals associated with cassiterite are columbite-tantalite, Nb-Ta rutile, with some tapiolite and samarskite. Cassiterite, columbite-tantalite and Nb-Ta rutile occur mainly as free particles and thus gravity separation can be used in the first stage, followed by magnetic and electrostatic separation techniques.

Nb-Ta-bearing minerals found in the heavy mineral fractions of alluvial deposits were studied, and their mode of occurrence described. Chemical compositions were determined mainly by electron-probe micro analysis, but x-ray fluorescence was also applied. Columbite-tantalite, Nb-Ta-rutile, wodginite and fersmite were recognised and their geographical distribution and geochemical compositions were delineated., Nb-Ta-bearing minerals found in the heavy mineral fractions of alluvial deposits were studied, and their mode of occurrence described. Chemical compositions were determined mainly by electron-probe micro analysis, but x-ray fluorescence was also applied. Columbite-tantalite, Nb-Ta-rutile, wodginite and fersmite were recognised and their geographical distribution and geochemical compositions were delineated.

The common Nb-Ta bearing minerals found associated with cassiterite were columbite-tantalite and Nb-Ta rutile, with some samarskite and tapiolite. In general these minerals had similar characteristics irrespective of the area they came from. The Nb-Ta bearing minerals were found to be closely associated with tin-bearing pegmatities along the Western Tin Belt of the Burma-Thai-Malaya orogen. Comparison of the general characteristics of Nb-Ta bearing minerals in Thailand and Malaysia is made., The common Nb-Ta bearing minerals found associated with cassiterite were columbite-tantalite and Nb-Ta rutile, with some samarskite and tapiolite. In general these minerals had similar characteristics irrespective of the area they came from. The Nb-Ta bearing minerals were found to be closely associated with tin-bearing pegmatities along the Western Tin Belt of the Burma-Thai-Malaya orogen. Comparison of the general characteristics of Nb-Ta bearing minerals in Thailand and Malaysia is made.

The mineralogical study of several products from the concentrator plant of Patana Mine, which was carried out by microscopic and electron microprobe examinations in polished sections, show that Nb-Ta bearing minerals which are found associated with cassiterite in the area are columbite-tantalite and struverite. Columbite-tantalite in general occurs as small inclusions in cassiterite, free particles, and intergrown with cassiterite and quartz in simple and mottled type of intergrowths. Struverite, which is less common than columbite-tantalite is present as inhomogeneous particles. The elements, Nb and Ta, which occur associated with cassiterite, are indicative of a pegmatitic origin and to a lesser extent a pneumatolytic origin. By applying carefully controlled magnetic and high tension separation to the magnetic products from the mine, it should be possible to obtain a columbite-tantalite concentrate with fairly high recoveries., The mineralogical study of several products from the concentrator plant of Patana Mine, which was carried out by microscopic and electron microprobe examinations in polished sections, show that Nb-Ta bearing minerals which are found associated with cassiterite in the area are columbite-tantalite and struverite. Columbite-tantalite in general occurs as small inclusions in cassiterite, free particles, and intergrown with cassiterite and quartz in simple and mottled type of intergrowths. Struverite, which is less common than columbite-tantalite is present as inhomogeneous particles. The elements, Nb and Ta, which occur associated with cassiterite, are indicative of a pegmatitic origin and to a lesser extent a pneumatolytic origin. By applying carefully controlled magnetic and high tension separation to the magnetic products from the mine, it should be possible to obtain a columbite-tantalite concentrate with fairly high recoveries.