w NEWSLETTER INTERNATIONAL TUNGSTEN INDUSTRY ASSOCIATION Rue Père Eudore Devroye 245, 1150 Brussels, Belgium Tel: +32 2 770 8878 Fax: + 32 2 770 8898 E-mail: [email protected] Web: www.itia.info The programme will begin on Tuesday Toxicologic Assessment for the Production and 19th evening with a Reception in the hotel jointly Mechanical Processing of Materials containing hosted by Tiberon Minerals and ITIA. Tungsten Heavy Metal. Not least will be an introduction to the formation of a Consortium to deal Working sessions will be held on Wednesday Annual with the implications of REACH on behalf of the and Thursday mornings and papers will tungsten industry, both legal and financial. include: General Readers will recall that REACH will place an obligation ▼ HSE work programme on individual companies to submit a technical dossier and register any chemical substance Meeting ▼ Ganzhou’s Tungsten Industry and Its Progress manufactured or imported into the EU in quantities ▼ Geostatistics in the mid and long-term planning for of more than 1 tonne. the Panasqueira deposit (Nuno Alves, Beralt Tin Tuesday 26 to and Wolfram) In order to assist companies with the registration process, the Commission recommends the creation ▼ Thursday 28 Paper by Zhuzhou Cemented Carbide of industry Consortia. These Consortia will enable the ▼ Update on Tiberon’s Development of Tungsten joint development, submission and sharing of September 2006 Mining in Vietnam information with the aim of reducing the compliance burden on individual companies and preventing ▼ Update on China’s Tungsten Industry Hyatt Regency Hotel, unnecessary additional animal testing. ▼ Update on US Tungsten Market (Dean Schiller, Boston, USA OsramSylvania Products) Both members and non-members will be equally ▼ Review of Trends in 2006 (Nigel Tunna, Metal-Pages) welcome to join the Consortium, saving themselves considerable amounts of money and time by so doing. The principal focus this year will be on HSE Issues (Wednesday morning), with reports from the leaders Registration and hotel reservation forms may be of ITIA’s extensive work programme and a short paper downloaded from the ITIA website (or contact the by Rheinmetall on Work Place Evaluation and Secretariat). NEW OFFICE PREMISES Membership Please ensure records are changed to reflect the move from Welcome to: London at the beginning of April of ITIA (and IMOA) to: Queensland Ores Ltd, Rue Père Eudore Devroye 245, 1150 Brussels,Belgium an Australian company which owns Wolfram Camp near Tel: +32 2 770 8878 Fax: +32 2 770 8898 Cairns and plans to bring the mine back into production in 2007. Email: [email protected] Website: www.itia.info Both Associations have always been registered under Rheinmetall Waffe Munition GmbH, Belgian Law and the proximity to allied organisations will a German company producing an extensive array of be advantageous. large and medium calibre tungsten-based ammunition. JUNE 2006 The ITIA’s Technical Consultancy continues its series on the many aspects of tungsten – MINERALOGY OF THE ELEMENT TUNGSTEN Wolf-Dieter Schubert and Erik Lassner Institute of Chemical Technologies and Analytics - Vienna University of Technology Tungsten does not occur in the earth’s crust elementally but only in less simplified ways. A typical respective example is the mineral the form of chemical compounds (minerals). Tungsten minerals are welinite, the formula of which is given as either quite rare because tungsten has a very low abundance in the Mn6[(W,Mg,Sb,Fe)O3][(OH)2|O|(SiO4)2] or as 6 universe (approx. 0.2 atoms W/10 atoms Si) and, consequently, also Mn6(W,Mg)2Si2(O,OH)14 in different publications. on earth (approx.1 microgram per gram corresponding Pinalite is a rare example of a tungsten oxyhalide (Pb3WO3Cl2). to 0.0001 %). Nevertheless, we know a variety of tungsten minerals. Economically important are only four of them: wolframite, Besides tungstates also tungsten acids and hydrated hübnerite, ferberite and scheelite which occur in sufficient tungsten oxides can be found as minerals. Examples are abundance and concentration in specific rocks. All others do not hydrotungstite - H2WO4·H2O (Fig.2), meymacite - have any economical value, as they are rare and occur in small WO3·H2O and tungstite - WO3·H2O. They are characteristic amounts only. They are generally called minor tungsten minerals. weathering products of scheelite or wolframite as well as products of hydrothermal alteration. In presence of aluminium- or iron- CHEMISTRY OF TUNGSTEN MINERALS bearing solutions, alumotungstite - (W,Al)(O,OH)3 or ferritungstite - (W,Fe)(O,OH)3 (Fig.3) may form. In regard to their chemical composition the majority of tungsten minerals belong to the group of tungstates. We distinguish If the oxygen in tungstates is substituted by sulfur or selenium we between monotungstates, as for example scheelite - CaWO4, talk about thio- or selenotungstates. Kiddcreekite is a ferberite - FeWO4 or hübnerite – MnWO4, and member of that rare class: Cu6SnW(S,Se)8. polytungstates which themselves can be iso- or heteropolytungstates. Isopolytungstates contain polymerized The last group of tungsten minerals belong to the sulphides with 6- 20- tungstate species like W6O21 or W12O46 . tungstenite - WS2 (Fig. 4) as example. In this compound the In heteropolytungstates additional foreign anions like silicate, tungsten atom is tetravalent (W 4+). phosphate, etc. are part of the chemical composition. In all these compounds tungsten is present as a six-fold positively charged central ion (W6+) which is either tetrahedrally or octahedrally Fig 1 coordinated by double negatively charged oxygen ions (O2-). An example for isopolytungstates is the mineral yttrotungstite - YW2O6 (OH)3 (Fig.1). Some of these minerals are very complex and the chemical formulas can be expressed in different, more or Fig.1: Yttrotungstite – YW2O6(OH)3 Kramat Pulai Mine, Malaysia; picture width 5 mm; Fig 2 Fig 3 copyright Thomas Witzke + Abraxas Verlag Fig. 2: Hydrotungstite H2WO4 · H2O – Japan; picture width 5 mm; collection of NHM Wien; copyright V.M.F. Hammer Fig.3: Ferritungstite (W,Fe)(O,OH)3 – Clara Mine, Rankach Valley, Germany; picture width 2mm; 2 copyright Stephan Wolfsried Fig 4 The crystal structure of scheelite consists of distorted WO4 tetrahedra linked to CaO8 polyhedra (Fig.5). The crystals have tetragonal symmetry and appear as dipyramidal pseudo-octahedra (Fig. 6). Colours range from golden yellow to orange, green to dark brown, Fig.4: Tungstenite WS2 – reddish gray, dark blue to black and colourless (if chemically pure). Crevola d'Ossola quarry, Italy; 2 mm crude flakes; Well-formed crystals are sought-after specimens for mineral copyright Maurice de Graaf collectors. Fig 5 GENESIS OF MINERAL FORMATION Most tungsten minerals form by crystallization from a hydrothermal liquid – the last liquid phase in the differential crystallization sequence of a magma (slow cooling process). Tungsten atoms, if present in magma, can not be incorporated in minerals of the first crystallization steps (basic rocks) because of the "wrong" size and charge of the tungsten ion (W6+). Also tungstate ions can not substitute silicate or aluminate ions in the later acidic crystallization step. Therefore, if tungsten is present in magma it will be concentrated in the residual hydrothermal liquid which is a supercritical liquid (around 600 °C and high pressure). Tungsten may be encountered as tungstate ion, tungstic acid, sodium tungstate or heteropoly acid. Depending on the presence and concentration of cations like Fe2+, Fig.5: The crystal structure of scheelite in projection along the b-axis with the unit cell outlined. Ca atoms are shown as blue Mn2+ and Ca2+ and the nature of the rocks surrounding the spheres and oxygen atoms as white spheres with a black rim; the WO4 tetrahedra are displayed as red polyhedra. hydrothermal liquid, different tungsten minerals crystallize (precipitate). The usual mineral paragenesis is ferberite, hübnerite and scheelite. In case the surrounding rock is a limestone (i.e. CaCO3) tungstate combines mainly with Ca forming scheelite. ECONOMICALLY IMPORTANT MINERALS Fig 6 Scheelite (Figs. 5-8) The mineral was named after the famous Swedish chemist Carl Wilhelm Scheele (1742-1786). It is chemically calcium tungstate, CaWO4. It represents the most abundant tungsten mineral on earth. Approximately two thirds of the known tungsten deposits contain scheelite. Scheelite can be found in pegmatites, hydrothermal veins and areas of contact metamorphism often Fig.6: Scheelite mineral specimens of different origin and colour; collection of NHM Wien; copyright V.M.F. Hammer associated with the minerals fluorite, muscovite, dolomite and orange (8ϫ7ϫ6 cm): Hiefelwand, Rauris, Austria (C.894) ϫ ϫ molybdenite. black (3 3 2 cm): Tae Wha, Korea (L 3572) green (4ϫ3ϫ5 cm): Fram Natas, Namibia (K 4611) transparent (5ϫ5ϫ5 cm): Felbertal, Salzburg, Austria (M 57) 3 Table 1: Physical and chemical properties of scheelite. The mineral stolzite (lead tungstate, PbWO4) is isotypic to Formula (pure) CaWO4 scheelite and can occur as a result of hydrothermal alteration of WO3 content [%] 80.6 scheelite (Fig.9). Crystal structure tetragonal dipyramidal Lattice parameters a [Å] 5.24-5.26 Scheelite is the most important raw material for the production of all c [Å] 11.37-11.40 tungsten compounds and the metal itself. c/a 2.163-2.169 Cleavage (010) distinct Specific gravity 5.9-6.1 The Wolframite Group Colour colourless, white, yellow, tan, orange, red, blue, black The wolframite group consists of iron