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Characterization and Study of the Preliminary Process Flowsheet of a Tungsten Ore, Final Report

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Characterization and Study of the Preliminary Process Flowsheet of a Tungsten Ore, Final Report GM 64322 CHARACTERIZATION AND STUDY OF THE PRELIMINARY PROCESS FLOWSHEET OF A TUNGSTEN ORE, FINAL REPORT KEN WRIGHT' Characterization and study of the preliminary process flowsheet of a tungsten ore FINAL REPORT No:T920 For: Mr. Ken Wright 408 Commercial Avenue Coos Bay, OR 97420 USA GM 64322 Prepared by: /eca.auth.!er M Sc: Coordinator riban, D.E:S. S°: Director Technology: Donal®" " éx, Eng , Ph.D.`; Date April a, 2008 ingu AU'"lAgF Ressources naturelles et Faune, Québec 0 2 AVR. 2009 1 7 AOUT 2009 ;l;néral t)i(ectiori JcrcNNVC"" DIR. INFORM. GÉOL. C„OREM 1180 rue, de la Minéralogie, Québec (Québec) GiN _1X7 Canada St' (418).527.8211. •'t "(418)';527-9188 GGE1,143 (2005.12=13); x 79 603 3 ii• SUMMARY Mr. Wright contracted COREM to conduct a mineralogical study of two (2) samples: a sample from a zone with tungsten between 5 and 15% (tungsten-rich sample) and a sample from a zone with about 37 ppm of gold (gold-rich sample). The Client requested to carry out also a literature review of existing flowsheets for tungsten bearing ore. The first goal was to identify major minerals and estimate the liberation sizes of tungsten phases and of gold. The second goal was to present a summary of existing process flowsheets found in the literature review. Both samples were composed of scheelite, pyrite, feldspars, carbonates, quartz, ferromagnesian silicate and apatite. Galena, magnetite and iron hydroxide were observed in the gold-rich sample. Liberation size of scheelite was between 53 and 75 pm in the tungsten-rich sample and below 38 pm in the gold-rich sample. Gold grain size was approximately 10 pm. In the literature review, a general process flowsheet was found and described. Usually, concentration of scheelite is achieved by gravity separation for coarse particles and by flotation for fines. Since a low-grade concentrate is obtained with flotation, chemical processes are used to produce a high-grade concentrate of synthetic scheelite. Typical industrial recovery of scheelite reaches between 60 to 80% with a final grade of 60 to 80% W03. COREM 1180, rue de la Minéralogie, Québec (Québec) G1N 1X7 Canada Project no. T920 (418) 527-8211 • a (418) 527-9188 G-GEN-13 (2005-12-13) CONTENTS Page SUMMARY ii CONTENTS iii TABLES iv FIGURES iv 1 INTRODUCTION 1 2 CONCLUSIONS AND RECOMMENDATIONS 1 2.1 Mineralogical study 1 2.2 Literature review and study of the preliminary process flowsheet 1 3 METHODOLOGY 2 3.1 Mineralogical study 2 3.1.1 Preparation of samples 2 3.1.2 Chemical analysis 2 3.1.3 Identification of major phases 2 3.1.4 Estimation of the liberation size 2 3.2 Literature review and study of the preliminary process flowsheet 3 4 RESULTS 3 4.1 Chemical analysis 3 4.2 Minerals identification 4 4.3 Estimation of the liberation sizes 5 4.3.1 Liberation size of scheelite 5 4.3.2 Gold habitus 7 4.4 Literature review and study of the preliminary process flowsheet 10 5 REFERENCES 15 APPENDIX A: Flowsheets from litterature 16 COREM 1180, rue de la Minéralogie, Québec (Québec) G1N 1X7 Canada Project no. T920 St (418) 527-8211 • L5i (418) 527-9188 G-GEN-13 (2005-12-13) iv TABLES Page Table 1: Chemical composition of the tungsten-rich sample by fraction 3 Table 2: Chemical composition of the gold-rich feed sample 3 Table 3: Liberation size estimation of scheelite in the tungsten-rich sample. 5 Table 4: Liberation size estimation of scheelite in the gold-rich sample. 5 FIGURES Page Figure 1: Tungsten-rich sample. py: pyrite, sc: scheelite. Darker phases are gangue. Optical microscope 20X 6 Figure 2: Gold-rich sample. py: pyrite, sc: scheelite, ma: magnetite. Darker phases are gangue. Optical microscope 20X. 6 Figure 3: Electrum associated with silver telluride and scheelite (SEM) 7 Figure 4: Free gold-silver telluride (SEM) 8 Figure 5: Gold-silver telluride as inclusions in pyrite (SEM) 8 Figure 6: Native gold and gold-silver telluride as inclusions in scheelite (SEM) 9 Figure 7: Gold-silver telluride as inclusion in quartz (SEM) 9 Figure 8: General flowsheet 1 12 Figure 9: General flowsheet 2 13 Figure 10: General flowsheet 3 14 COREM 1180, rue de la Minéralogie, Québec (Québec) GIN 1X7 Canada Project no. T920 Sr (418) 527-8211 • EiJ (418)527-9188 G-GEN-13 (2005-12-13) 1 1 1 1 1 INTRODUCTION COREM was mandated to carry out a mineralogical study of two (2) hand-picked samples : a sample from a zone with tungsten between 5 and 15% (tungsten-rich sample) and a sample from a zone with about 37 ppm of gold' (gold-rich sample). A preliminary literature review of existing concentration flowsheets of tungsten ore was also requested. 1 2 CONCLUSIONS AND RECOMMENDATIONS 1 2.1 Mineralogical study It was found that the tungsten-rich sample is mainly composed of scheelite, pyrite, 1 feldspars, carbonates, quartz, ferromagnesian silicate and apatite. The gold-rich is composed of scheelite, pyrite, magnetite, iron hydroxide as oxidation of pyrite, feldspars, carbonate, quartz, ferromagnesian silicate, galena and apatite. Gold was observed as 1 native gold, electrum and "gold-silver telluride" (calaverite). 1 Liberation size of scheelite is between 53 and 75 pm for tungsten-rich sample and below 38 pm for gold-rich sample. Gold grain size is approximately 10 pm for the gold-rich 1 sample. The liberation size of gold was not evaluated in the tungsten-rich sample. 1 2.2 Literature review and study of the preliminary process flowsheet Usually, the concentration of scheelite is achieved through gravity separation techniques (coarse particle) and/or flotation (fine particles). Flotation is often required to get rid of l' sulfides. Scheelite contentrates obtained with solid/solid separation devices often need to be upgraded by chemical processing to produce high-grade synthetic scheelite 1 concentrate. Recovery of scheelite typically ranges between 60 to 80% with a final grade of 60 to 80% W03. 1 Since mineralogical study of tungsten-rich and gold-rich samples showed that the liberation size of scheelite is below 75 pm and 38 pm respectively, a thorough investigation 1 of available concentration processes should be conducted. In particular, the benefits of the 1 COREM 1180, rue de la Minéralogie, Québec (Québec) G1N 1X7 Canada 1 Project no. T920 WI (418) 527-8211 • 5i (418) 527-9188 G-GEN-13 (2005-12-13) 1 2 flotation and leaching processes should be weighed against the low operating cost of gravity separation techniques. 3 METHODOLOGY 3.1 Mineralogical study 3.1.1 Preparation of samples The two samples were ground at 100% -35 Mesh (425 pm). The gold-rich sample was concentrated with heavy liquid (tetrabromoethane of density 2.96). The concentrate of the gold-rich sample and all the tungsten-rich sample were sieved in order to produce samples of various granulometric fractions. Polished sections were made for four (4) fractions of the tungsten-rich sample (100 to 150 mesh, 150 to 200 mesh, 200 to 270 mesh, 270 to 325 mesh ; 150 to 106 pm, 106 to 75 pm, 75 to 53 pm, 53 to 45 pm) and four (4) fractions of the gold concentrate of the gold-rich sample (150 to 200 mesh, 200 to 270 mesh, 270 to 400 mesh, minus 400 mesh; 106 to 75 pm, 75 to 53 pm, 53 to 38 pm, minus 38 pm). One polished section was also made with the tailing of the gold-rich sample (all particle sizes). 3.1.2 Chemical analysis Gold and silver titration were achieved by fire assay and atomic absorption, respectively. Chemical analysis of the other elements was done by X-ray fluorescence. 3.1.3 Identification of major phases The identification of major phases was performed by optical microscope, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). 3.1.4 Estimation of the liberation size The estimation of the liberation size of Au-bearing and W-bearing phases was performed on polished sections by optical microscope, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Evaluation was made by counting W-bearing particles. COREM 1180, rue de la Minéralogie, Québec (Québec) G1N 1X7 Canada Project no. T920 St (418) 527-8211 • (418) 527-9188 G-GEN-13 (2005-12-13) 3 3.2 Literature review and study of the preliminary process flowsheet A literature review about conventional processes and flowsheets of some mills was achieved. 4 RESULTS 4.1 Chemical analysis Tables 1 and 2 present the chemical composition of the tungsten-rich and gold-rich samples. Tungsten and gold are in grey. Table 1: Chemical composition of the tungsten-rich sample by fraction. +150M -100M +200M -150M +270M -200M +325M -270M Al (%) 5 5 5 5 Ba (%) 0.1 0.1 0.1 0.1 Ca (%) 6 8 8 8 Fe (%) 3 3 3 3 K (%) 4 4 4 4 Mg (%) 1 1 1 1 Mn (%) 0.1 0.1 0.1 0.1 Na (%) 2 2 2 2 O(%) 53 50 48 48 P (%) 0.2 0.3 0.4 0.4 S (%) 1 1 1 1 Si (%) 15 15 14 14 Sr (%) 0.2 0.2 0.2 0.2 Ti %) 0.2 0.2 0.2 0.2 The silver content of the tungsten-rich feed sample is 5.8 mg/kg. From Table 1, we can see that chemical composition is very similar from a fraction to another. This means that mineralogical composition is probably uniform in all size fractions. Uniformity is easy to understand for gold as it is finely disseminated in other particles.
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