Niobium:  Mining,  Production  and  Applications  

 

P r o c e s s   E n g i n e e r i n g ,   K T H ,   2 0 1 3  

Niels  Cautaerts  Mikael  Sandell  Khalid  Hannan  Pengcheng  Cao  Miranda  Jing  

Materials Science, KTH, 2013

Mining, Production and Applications of NiobiumNiels Cautaerts, Mikael Sandell, Khalid Hannan, Pengcheng Cao, Miranda Jing

AbstractThe process of mining, extraction and production of Niobium metal and its alloys are discussed. The worldwide economicimpact of its applications is evaluated. The possibility of Sweden playing a role in Niobium production is investigated.

Contents

Introduction 1

1 Discovery, Mining and Processing (Khalid) 11.1 Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Natural occurrence, mining and processing . . . . . . . 1

2 Production Processes (Niels) 22.1 Ore concentration . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Chemical separation from Tantalum . . . . . . . . . . . . 32.3 Aluminothermic reduction . . . . . . . . . . . . . . . . . . . 32.4 Other reduction and purification mechanisms . . . . . . 42.5 Forming and heat treatments . . . . . . . . . . . . . . . . 4

3 Properties and Applications (Miranda) 43.1 Physical Properties . . . . . . . . . . . . . . . . . . . . . . . 43.2 Chemical Properties . . . . . . . . . . . . . . . . . . . . . . 43.3 Applications of Niobium . . . . . . . . . . . . . . . . . . . . 4

Superconducting Materials • Numismatics • Cathodic Protection

3.4 Properties of Niobium Alloys . . . . . . . . . . . . . . . . . 53.5 Applications of Niobium Alloys . . . . . . . . . . . . . . . . 5

Arc Welding • Superconducting Magnets • Surgical Implants

4 Global consumption, Reserves, Environmental impactand other aspects of Niobium (Pengcheng) 5

4.1 Global consumption . . . . . . . . . . . . . . . . . . . . . . 54.2 Reserves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.3 Environmental Impact . . . . . . . . . . . . . . . . . . . . . 64.4 Other aspects about Niobium . . . . . . . . . . . . . . . . 6

Price • Recycling • Health Impact

5 Producing Niobium in Sweden (Mikael) 7

References 7

IntroductionNiobium, a chemical element with the symbol Nb and atomicnumber 41, is a soft and rare transition metal which is usedas an alloying agent in high grade steel production [1]. Steelalloyed with niobium becomes stronger, lighter in weightand can withstand highly corrosive environment. Thus, steelcontaining niobium has a wide range of use in automotive,gas pipeline and construction industries [2].

1. Discovery, Mining and Processing(Khalid)

1.1 DiscoveryNiobium was named after the character from Greek mythology“Niobe”, daughter of Tantalus, a character which could notdrink. It was named so because of its occurrence with tantalumand sharing similar properties. Niobium belongs to group fiveand sits just above tantalum in the periodic table. Niobiumwas first discovered by English chemist Charles Hatchett in1801. It was first found in American ore which had beensent to England and it was named columbium. Later in 1846,German chemist Henrich Rose discovered it independentlyand named it niobium which is the name that later in 1950was adopted by IUPAC. Since niobium shares very similarphysical and chemical properties with tantalum they are hardto distinguish [4].

1.2 PropertiesNiobium is a shiny, greyish white, ductile and paramagneticmetal. In air, it forms an oxide layer and due to this oxidelayer it has good corrosion resistance properties. It also ex-hibits good superconductive characteristics. It has a very highmelting (2468ºC) and boiling point (4930 ºC). Despite havinga high melting point, it has lower density than other refractorymetals [2].

Figure 1. Niobium in its natural state

1.3 Natural occurrence, mining and processingNiobium, as an elemental metal, is not found in nature. Rather,it occurs in various minerals. Niobium containing miner-als contain also tantalum and their oxides are present inearth’s crust. Niobium minerals in deposits are most oftenblended with igneous rocks [5]. Pyrochlore and columbite

Mining, Production and Applications of Niobium — 2/8

Table 1. Different Niobium minerals

Mineral Chemical formula Crystalline form Density g/cm3 % Nb2O5Pyrochlore (Na, Ca)2(Nb,Ta)2O6(OH,F) Cubic 4.3 63.6Niobite (Fe, Mn) (Nb,Ta)2O6 Ortho-rhombic 5.3 78.0Euxenite (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6 Ortho-rhombic 5.0 41.4Samarskite (Y,Ce,U,Ca,Fe,Pb,Th)(Nb,Ta,Ti,Sn)2O6 Ortho-rhombic, dipyramidal 5.0 46.4

Table 2. Mine production in tons per year. [3]

Country 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011Brazil 26000 29000 29900 35000 40000 57300 58000 58000 58000 58000Canada 3410 3280 3400 3310 4167 3020 4380 4330 4420 4400World 29900 32800 34000 38700 44500 60400 62900 62900 62900 63000

(niobite) are the main minerals from which niobium is ex-tracted. Other minerals containing niobium are Betafite, Eux-enite, Samarskite and Struverite [6].

Pyrochlore is mined for its niobium content. When columbiteis mined, niobium can be extracted as a byproduct. The largestdeposits of niobium were found in Brazil and Canada and bothof these two countries account for most of niobium produc-tion (2001) [7]. Two of the world’s largest deposits namelythe Araxa and the Catalao deposits are located in Brazil andowned by CBMM and AngloAmerican. IAMGOLD Cor-poration owns the third largest deposit which is located inQuebec, Canada. Araxas reserve of pyrochlore is about 460million tons which is sufficient to meet world’s demand forabout 500 years. Mining of Araxas pyrochlore ore gradesbetween 2-3% of Nb2O5. Catalao has a reserve of 18 mil-lion tons of pyrochlore and its content of Nb2O5 is about1.34%. Canada’s Niobec mine has a reserve of about 18000tons of pyrochlore. The largest niobite mining is in operationin Pitinga, Brazil. Reserves are estimated to 201 million tonsat 0.223% of Nb2O5 [6].

Open pit mining is the method that is prevalent in Brazilwhile Niobec mine in Canada, is the only underground mine inthe world. Open pit mining hardly exceeds 100 meters. Whenthe deposit becomes too deep and open pit mining becomesvery expensive then underground mining is used. Waste toore ratio or strip ratio is another decisive factor for choosingunderground mining. Open pit mining becomes economicallyless feasible once the ratio becomes large. Reason for usingdifferent mining process depends also on the physical andchemical properties of the ore mineral, the tonnage and grade,the shape, depth and geometry of the ore body [5].

Once the ore is mined, it is then ground finely and benefici-ated by flotation and high intensity magnetic separation to getrid of the iron minerals [2]. Once separated from other miner-als, the mixed oxides of tantalum and niobium are obtainedand in a subsequent stage are treated with hydrofluoric acid.Thus complex niobium and tantalum fluorides are formed andthese fluorides are extracted from aqueous solution by usingorganic solvents. Later, these complex fluorides can either beprecipitated as potassium fluoride complex or as pentoxides

by the addition of ammonia. These steps are followed bywashing, filtration and calcination to oxide [8]. Nitric acid isused in Canada to remove apatite while in Brazil, reductionof barium, phosphorus and sulphur content is being done by achloride leach process. After this physical processing, a py-rochlore concentrate grading 55-60% Nb2O5 is achieved [2].Two separate methods are used during niobium production;aluminothermic process or by reduction in an electric arc fur-nace. The company CBMM can produce very pure oxideswhich can be used to produce vacuum grade ferroniobium,nickelniobium as well as metal ingots after electron beamtreatment [6]. Nb2O5 can be used as the starting materialfor the production of a variety compounds such as niobiumchloride (NbCl5), niobium carbide (NbC) or lithium niobate(LiNbO3). Niobium metal manufactured by aluminothermicreduction of the oxide is followed by electron beam refining.Niobium pulver can be prepared by the reduction of K2NbF7with sodium or by the reduction of niobium oxide with mag-nesium [6]. A simplified process steps for manufacturing ofniobium in CBMM is presented in figure 2.

Figure 2. process steps in niobium production at CBMMfacility

Mining, Production and Applications of Niobium — 3/8

2. Production Processes (Niels)The type of processes following the mining of the mineralwill depend heavily on the type of mineral, the types of rockpresent, as well as the purpose the Niobium will serve.

2.1 Ore concentrationPhysical and chemical processing of the ores will be mostlydependant on the type of mineral. Since 99% of Niobiummining is located in Canada and Brazil [5], and since in bothof these locations the main source of Niobium is Pyrochlore,the focus here will be on Pyrochlore enrichment.

Niobec, a mine and IAMGOLD company located in Que-bec, Canada, produces ferroniobium bij mining pyrochlore,concentrating Nb2O5, then reducing the oxide by an alu-minothermic reaction [9]. Their proces, detailed here, iscomprised of a series of physical and hydrometallurgical stepssummarized in figure 3. First the ore must go through a seriesof crushers and grinders to produce a fine dust. The crushedrock is then mixed with water to make a slurry, which is fedthrough a series of cyclones to remove slime comprised ofvery small particles of the order 10 µm. This is done to fa-cilitate the froth flotation process that follows. The slimeoverflow is sent to a water recovery unit. Some noibium isinevitably lost in this process. The underflow, rid of slime, ismixed with sodium silicate and a specific fatty acid surfactant,and then fed to a floatation cell. First floatation is carried outto remove carbonates. The surfactant attaches preferably tothe calcium carbonate particles and causes them to float up sothey can be scrapped off the surface, separating it from otherparticles. This floatation process must be repeated a numberof times to achieve a good removal. Carbonate must selec-tively be removed first, otherwise it would float up along withthe pyrochlore in a following step. What is left is then sentto floatation cells to float of pyrochlore in the same manner.Here tallow diamine acetate is used as surfactant. Pyrochlorehas very similar surface properties to other common mineralsand rocks, therefore the choice of collector and pH must bevery specific. Sulfides still float with the pyrochlore however;they must be floated of with another specific surfactant: PAX.The slurry is then sent into a tank where it is leached with HClto remove trace phosphates. Another floatation for removalof sulfides is then implemented before the slurry is sent to adryer where all moisture is removed. If the ore also containssignificant amounts of iron, a magnetic separation step canalso be inserted [5].

2.2 Chemical separation from TantalumPyrochlore is a mineral that contains very little Tantalum, andthus for standard grade Ferroniobium this impurity is tolerable.In other minerals however, Niobium and Tantalum are oftenfound together, and since some niche applications require veryhigh purities in the metal, a chemical process must sometimesbe employed to separate the two oxides. Both metals have verysimilar chemical properties so this is difficult to achieve. Firstthe ore concentrates are dissolved in a mixture of hydrofluoric

Figure 3. Pyrochlore concentration process

and sulfuric acid. Adding a substance like isobutyl ketoneextracts both metals to the organic liquid phase. This has asadded advantage that other impurities such as iron are leftbehind in the aqueous phase [5]. Adding sulfuric acid willremove the niobium from solution but not the tantalum [1].Many more processes, both industrial and lab scale, exist,and they are detailed in Wilkinson’s [10] and Ayanda andAdecola’s work [11].

2.3 Aluminothermic reductionAfter an oxide concentrate is obtained, there exist many waysto reduce it to the metalic form. The method used dependson the required purity for the application the Niobium willbe used for. Since 75-80% by weight of worldwide Niobiumproduction goes into making ferroniobium [2] (a concentratedalloy of iron and niobium) the focus here will be on the Alu-minothermic process.

At Niobec [9], to reduce the pyrochlore concentrate, it isadded to the converter, together with aluminum flakes and asource of iron oxide. Sodium nitrate is also added. It is anoxidizer that helps move the reaction forward. Calcium oxideis also added to reduce the fusion point of the slag that willbe formed during the reaction. The slag will consist mostlyof aluminum oxide. In figure 4 it can be seen that adding theright amount of calcium oxide reduces the melting point ofaluminum oxide significantly, allowing the slag to stay liquidlonger which facilitates a better separation from the metal.

The mixture of oxides and aluminum is then lit to reducethe Niobium and Iron into metallic form according to thefollowing reactions.

Fe2O3+2Al→ Al2O3+2Fe3Nb2O5+10Al→ 5Al2O3+6Nb

Mining, Production and Applications of Niobium — 4/8

Figure 4. CaO-Al2O3 phase diagram (www.npl.co.uk)

The intense heat generated in these reactions allows themixture to be liquid sufficiently long for the slag and metallicphase to separate. Upon solidification, the slag is dumpedback into the ground and the ingot with 60-70% Nb is shippedoff for further processing. The converter can then again becharged.

2.4 Other reduction and purification mechanismsThere exist multiple methods of reducing the concentrated ore.The aluminothermic method suffices for ferroniobium but isinsufficient for where higher grades of purity are required.

Niobium can also be reduced with carbon for example[10]. First cokes are let to react under vacuum and at 1800°Cwith niobium oxide to produce niobium carbide. This then isreacted again with niobium oxide to produce niobium metal.

Nb2O5+5NbC→ 5CO+7Nb

While the aluminothermic reaction produces a solid brittleingot, the reduction with carbon produces a niobium sponge.There also exists an electrolytic way to reduce the Niobium.KCl, KF, K2NbF7 and a small amount of Nb2O5 are fused at750°C and a current is applied. The niobium then deposits asa solid onto the electrodes. The output from the aluminother-mic method (without addition of iron) can also be subjectedto electron beam refining to achieve higher purity. More de-tailed and less common ways of reduction are detailed inWilkinson’s work [10].

2.5 Forming and heat treatmentsOnce the metal has been made, either as niobium or ferro-niobium, forming procedures and heat treatments may beemployed. Ferroniobium ingots are often crushed into smaller

bits and these are then added to electric arc furnaces togetherwith steel to produce HSLA steel used in construction. Nio-bium as trace alloying element in this application is its mainworldwide use, even at concentrations of 0.1% by weight.Niobium forms a carbide which pins grain boundaries andthus acts as a grain refiner. It can also form precipitates to im-prove strength [12]. The increase in strength is so significantthat a lot less steel has to be used than if Niobium wasn’t analloying agent. For example, the bridge connecting Swedenand Denmark contains .022% Niobium, but that meant that 15kilotons of steel were saved. [2]. Typically, Niobium steels aresubjected to controlled rolling, which is a process in whichthe forming and heat treatment are combined. In this pro-cess, recrystalization takes place and the Niobium precipitatesform. Plates and bars are made for use in construction. Thesecan be welded as well as joined mechanically with bolts orrivets [12].

Niobium not alloyed with steel is used in making super-alloys, containing nickel, titanium, zirconium and other raremetals for aerospace applications. Details on workability andheat treatments of these alloys are difficult to find, with somedetailed in papers collected in reference [13]. Pure Niobiumis almost never used, save for in niche applications such asjewelry.

3. Properties and Applications (Miranda)

Figure 5. A piece of niobium metal)

Niobium, formerly called Columbium(Cb), is a chemicalelement with the symbol Nb and its standard state is solid at298K.

3.1 Physical PropertiesBeing a transition metal in the group 5 of the periodic table,Niobium possesses the following properties: soft (it relies onthe purity: purer means softer), lustrous and ductile. When amagnetic field is applied, it will be attracted. This is calledthe property of paramagnetism.

Generally, most of the transitional metal could be usedas superconductor, as is the case with Niobium. When the

Mining, Production and Applications of Niobium — 5/8

Table 3. Properties of Niobium [14]

Symbol NbAtomic Number 41Atomic Weight 92.91Melting Point 2750 KBoiling Point 5017 KDensity of Solid 8570 kg m−3

Crystal Structure Cubic

temperature is low enough to reach 9.2K, it becomes super-conducting and the level of this depends on the purity.

In addition, Niobium has another property that makes itbeing used in the nuclear industries: the low capture cross-section for thermal neutrons [3].

3.2 Chemical PropertiesAt a high temperature, Niobium begins to oxidize and whenbeing exposed to the air for a long period, it takes on a colorof light blue.

Furthermore, it has the ability to withstand the chemicalbreakdown under specific environment by forming dielectricoxide layers.

3.3 Applications of Niobium3.3.1 Superconducting MaterialsSince having the property of superconductivity, Niobium iswidely used in the particle accelerators. It can activate ahuge accelerating electric field with a relatively small amountof power and this superior property reduces the size of theaccelerator [15].

3.3.2 NumismaticsMixed with gold and silver, Niobium is often used to makecommemorative coins. Due to the typical and special colorafter oxidizing, it adds value and significance to the coins.

3.3.3 Cathodic ProtectionTo prolong the service life of platinum-plated water tanks,Niobium is used in the anodes to form an electrochemicalsystem. It is more active so that the cathode(Platinum) won’treact with the air, in other words, the cathode can be protected.

3.4 Properties of Niobium AlloysNiobium is used mostly in alloys and it improves the strengthof the steel although the content of Nb is normally less than0.1%. Adding niobium to the steel results in the formationof niobium carbide and niobium nitride existing in the alloyand these compounds improve the grain refining, retardationof recrystallization, and the rate of hardening of the steel.These improvements further increase the toughness, strength,formability, and weld ability of the alloys.

3.5 Applications of Niobium AlloysNiobium is mainly used for the production of high-temperature-resistant alloys and special stainless steels. Some of these

alloys are strong so they are used in pipe construction whileothers with high-temperature-resistance and high-stability areusually used for nuclear reactors, jets, missiles, cutting tools,supermagnets and welding rods [16].

3.5.1 Arc WeldingActing as a stabilizer, Niobium is added in the welding mate-rial and forms a steady carbide to increase the welding abilityand the corrosion-resistance of the welding line.

3.5.2 Superconducting MagnetsNiobium alloys (mostly Niobium-Tin, Niobium-Germaniumand Niobium-Titanium alloys) help to visualize the internalstructures and image nuclei of atoms in MRI (magnetic res-onance imaging ) and NMRI (nuclear magnetic resonanceinstruments). The other usage is in the particle accelerators,where these superconducting magnets accelerate the particleto a specific velocity under a certain time.

3.5.3 Surgical ImplantsNiobium alloys are physiologically inert and thus hypoaller-genic, so they are used in surgical implants since they have noreaction with human tissue.

4. Global consumption, Reserves,Environmental impact and other aspects

of Niobium (Pengcheng)

4.1 Global consumptionAccording to a report by the IAMGOLD Corporation, produc-ers of Standard-Grade Ferroniobium hold a 90.2% share of theniobium market [2]. Standard-Grade Ferroniobium is appliedmostly in steel production. Therefore, the steel industry isthe major consumer of niobium. Figure 6 shows the marketshares of different niobium products.

Figure 6. Proportions of Niobium Market [2])

In 2011, the global consumption of Ferroniobium is over90,718 tons, and it is growing at 5% to 7% per year [17].The growth of global demand for niobium is driven by two

Mining, Production and Applications of Niobium — 6/8

main factors: First of all, since the steel industry is the majorconsumer of niobium, a demand for steel drives a demandfor niobium. Chart 7 shows the ferroniobium consumptionand steel production from 2000 to 2010. It is obvious thatthe ferroniobium consumption is tightly connected with steelproduction. This also means that economic growth plays animportant role in niobium consumption because it is highlycorrelated with transportation, construction and oil and gassectors, which are the largest consumers of steel.

Figure 7. Ferroniobium consumption and steel production,2000-2010 [2])

Secondly, focusing on the amount of niobium used in ev-ery ton of steel, increasing quantity is being added in orderto produce higher grade of steel. With developments of newtechnology, industrial standards, energy saving requirements,etc., consumers require steel products of higher quality. There-fore, steel producers have been increasing niobium additioninto their products due to the benefits from niobium’s additionto the steel’s properties. In order to produce higher grades ofsteel, 40 grams of ferroniobium were added per ton in 2000and it went up to 63 grams by 2008 [2].

Concerning the future of the niobium market, the steelindustry will still be the major consumer for a long time. Inthe meantime, it is noteworthy that BRICS countries (Brazil,Russia, India, China and South Africa) will be an importantelement in the future niobium market, especially China, whohas the fastest economic growth and largest steel production.In 2010, global GDP increased by 5.1% largely due to strongperformance by the BRICS economies which grew 8.8% [2].As is discussed above, a positive economic outlook guaranteeshigh demand for steel products. The GDP growth of theBRICS countries is fuelling the demand for steel products andconsequently influences the demand for niobium. Chart 8 andChart 9 indicate the percentage of BRICS steel production in2012 and the rising trend from 2010 to 2013 based on statisticsof World Steel Association.

4.2 ReservesNiobium resources mostly locate in Brazil and Canada. How-ever, other countries also own unquantified niobium resources,including Egypt, Malawi, Greenland, Russia, Mongolia, Congo,Finland, Saudi Arabia, Nigeria, Mozambique and etc. Spe-cially in some countries like Mozambique and Congo, thereserves were radioactive which were quite dangerous formining. The total amount of global niobium ore reserves, in-

Figure 8. Compare of steel production between BRICScountries and the rest of the world in 2012 [18])

cluding proved and probable, are estimated to be 485 milliontons with about 93 percent in Brazil. [5]. Table 10 indicatesthree major reserves and the total amount.

4.3 Environmental ImpactMining of columbite can environmental problems. For exam-ple, based on a research on Environmental effect of mineralexploitation in Nigeria [19], the mining of columbite hascaused a number of environmental damages, including air,land and water pollution, damage of vegetation, ecologicaldisturbance, landscape degradation, geological and radiationhazards.

4.4 Other aspects about Niobium4.4.1 PriceChart 11 presents the price performance of niobium from 2000to 2010. It shows that the price fluctuated between US$12.38and 14.50 in the first half of 2000s. After 2005, the pricebegan to soar due to the rise of steel production. It peakedat US$36.75 in 2008 and remained at about US$32. Sincethe demand for niobium continues to boom, the price is notexpected to have a distinct drop.

4.4.2 Recycling20% of niobium consumption is estimated to be recycled. Itis recycled from niobium-bearing steels and super alloys [20].However, the amount of niobium recycled from scrap recoveryis limited.

4.4.3 Health ImpactAccording to the website of Lenntech [16], inhaled niobiumis retained mainly in the lungs and bones, interfering withcalcium as an activator of enzyme systems. When people

Mining, Production and Applications of Niobium — 7/8

Figure 9. Percentages of BRICS steel production in theworld from 2010 to 2013(Aug) [18])

Figure 10. Major niobium ore reserves and its totalamount [5])

are exposed at 40mg/m3 of niobium nitride, it could lead toscarring of the lungs after inhalation. Meanwhile, tantalumand niobium minerals such as Coltan are considered to containsome levels of thorium and uranium, usually high enough tobe considered radioactive.

5. Producing Niobium in Sweden (Mikael)In Sweden currently niobium is not produced. There areseveral deposits available throughout the country containingboth niobium and tantalum ores [6]. Figure 12 shows depositsin Sweden where both niobium and tantalum ores are present.

The deposits in the area surrounding Ostersund and Sundsvallcontain five deposits; Raggen, Jarkvissle, Orrvik, Gammod-berget and Stockberget, which contain columbite mineraliza-tion. Raggen and Jarkvissle contain ore deposits of 200000and 600000 tonnes respectively, however the percentage ofniobium is not known. Jarkvissles main ores are pegmatite,spodumene-petalite and cassiterite. Orrviks is almost thesame but with spodumene instead of the micture spodumene-petalite. Raggens, Gammodbergets and Stockbergets main

Figure 11. Niobium price performance from 2000 to2010 [2])

Figure 12. Map of Swedish deposits which contain niobiumand tantalum ores)

ore is pegmatite.Holmslattmyren contain betafite ores which contain nio-

bium, tantalum and uranium. However the amount of betafiteore in Holmslattmyren is low due to the fact that the mainore in that deposit is made up of nepheline syenite. Also theuranium makes the ores radioactive.

Investigations of a deposit at Akersjon show a presenceof alkaline ores as well as heightened levels of radioactivity.The presence of niobium has not been confirmed and what iscausing the radioactivity has yet to be established.

Olserum, one of the larger deposits, mainly consists ofmagnetite with a content of 300 ppm of niobium. Other thanthat the deposit also consists of 0,8 % rare metals, such ascerium and yttrium, and some of the present ores containuranium and thorium.

The deposit at Uto in the archipelago of Stockholm mainlyconsists of pegmatite but also some amount of niobium bear-

Mining, Production and Applications of Niobium — 8/8

ing ores.Varutrask consists mainly of pegmatite as well but contain

some columbite enclosed in the other ores.Despite having these available deposits it is not economi-

cally viable to start mining it in Sweden both due to the factthat it is more cost efficient to import it from other countriesand that the refining process of the ores in Sweden doesn’tproduce an acceptable percentage of niobium. A test miningwas done on 20 kg of ore from Holmslattmyren and after sev-eral trials using flotation it was found that it was hard to findan enrichment process that would obtain a product containingmore than 20 % Nb2O5. This percentage is not economicallyfeasible to mine and refine further. It is also a fact that thedeposits that currently exist in Brazil will be enough to main-tain the global needs for another 500 years so the economicincentive to start mining for niobium in Sweden is practicallynonexistent. Other than the economic aspects, the radioactiv-ity that is present in some of the deposits make up anotherproblem that needs to be dealt with in order to commence themining of niobium ores.

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[13] The science and technology of tungsten, tantalum, molyb-denum, niobium and their alloys, 1963.

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