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

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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.

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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.

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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

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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

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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

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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.

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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.

Table 2: Chemical composition of the gold-rich feed sample.

1 Gold analysis was done on duplicates: results presented are the averages.

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AI (%) 3,6 Ba (%) 0,06 Ca (%) 13 Fe (%) 6,3 K (%) 2,4 Mg (%) 1,5 Mn (%) 0,15 Na (%) 1,4 O(%) 43 P (%) 0,43 Pb (%) 0,04 S (%) 0,69 Si (%) 25 Sr(%) 0,11 Ti (%) 0,33

Ag (mg/kg)

Gold was concentrated from 7 mg/kg to 21 mg/kg in heavy part. Light part contains 5 mg/kg. Concentration was not perfect but it was sufficient to observe gold in a representative number.

4.2 Minerals identification

SEM-EDS and optical microscopy analysis of the samples identified tungsten bearing ore as scheelite. For both samples, pyrite, feldspars, carbonates, quartz, ferromagnesian silicate and apatite were also found. In the gold-rich sample, magnetite, iron hydroxide as oxidation of pyrite and galena were found. Gold was observed as native gold, electrum and "gold-silver telluride".

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5 1 4.3 Estimation of the liberation sizes

The liberation size of scheelite was investigated on the gold-rich sample and the tungsten- rich sample. Gold habitus was done on the gold-rich sample only.

4.3.1 Liberation size of scheelite

For the liberation sizes of the scheelite, a particle was considered liberated if more than 95% of the total particles was scheelite.

Tables 3 and 4 give the percentage of volume of scheelite liberated in both samples.

Table 3: Liberation size estimation of scheelite in the tungsten-rich sample.

Mesh Tyler Diameter % vol -100 +150 M -150 +106 pm 70 -150M +200 M -106 +75 pm 76 -200M +270 M -75 +53 pm 86 -270M +325 M -53 +45 pm 92

Table 4: Liberation size estimation of scheelite in the gold-rich sample.

Mesh Tyler Diameter % vol -150 +200 M -106 +75 lam 53 -200M +270 M -75 +53 pm 60 -270M +400 M -53 +38 pm 62 -400 M -38 pm 73

The liberation size of scheelite was estimated to be between 53 to 75 pm (270 to 200 M) for tungsten-rich sample and below 38 pm (400 M) for gold-rich sample.

Figures 1 and 2 show examples of scheelite in tungsten-rich and gold-rich samples.

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Figure 1: Tungsten-rich sample. py: pyrite, sc: scheelite. Darker phases are gangue. Optical microscope 20X.

Figure 2: Gold-rich sample. py: pyrite, sc: scheelite, ma: magnetite. Darker phases are gangue. Optical microscope 20X.

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4.3.2 Gold habitus

Ten gold bearing particles were found in the gold-rich sample. These particles were made of native gold, electrum or in a mix of gold-silver telluride. They were mostly in middling particles as fine inclusions in pyrite, scheelite and quartz. Figures 3 to 7 show some examples of Au bearing phases. Diameter of inclusions and particles are mostly below 10 pm.

Figure 3: Electrum associated with silver telluride and scheelite (SEM)

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000000 WD15.7mm 20.0kV x7 .0k Sum

Figure 4: Free gold-silver telluride (SEM)

Figure 5: Gold-silver telluride as inclusions in pyrite (SEM)

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Figure 6: Native gold and gold-silver telluride as inclusions in scheelite (SEM)

Aq-Te~ .~ Au-Ag-Te .NA.

quartz

galena

BSE2 05—Feb-08 000000 WD15-5mm 20.0kV x350 10 Oum

Figure 7: Gold-silver telluride as inclusion in quartz (SEM)

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4.4 Literature review and study of the preliminary process flowsheet

The common way to concentrate scheelite is first to crush and mill the ore to liberate tungsten mineral phase. Scheelite ore can be concentrated by gravimetric methods, often combined with froth flotation. Scheelite having a density of about 6, gravimetric methods alone may give high-grade concentrates. However, flotation may be used alone. Ore concentrates in international trading require 65 to 75 % WO3 (80 to 93% scheelite).

General flowsheets are presented in Figures 8, 9 and 10. Flowsheet study shows dimension for crushing from 1" to 6 mesh and for grinding from 12 mesh to as little as needed. Ig old ispresent, a jig is used to concentrate the ore before grinding.

Flowsheets differ one from another in the way sheelite is concentrated. In flowsheet 1 (Figure 8), gravity separation is used. Depending of the size, separation is done by jigging, grinding and tabling for coarse ones, with spirals and tables for medium ones and with cyclones and tables for fines. Tail can be floated to concentrate scheelite but this step is optional. Middling particles are generally reground and recovered by gravimetric methods. Concentrate is floated to remove sulfides. Tail of sulfide flotation gives scheelite concentrate. If so, magnetic mineral may be removed by magnetic separation. If sulfide phase is pyrite only, roasting and magnetic separation can be used alone instead of flotation. Sulfide concentrate may be used to recover gold if present. Instead of sulfide flotation, a scheelite flotation can be done to concentrate.

Flowsheet 2 (Figure 9) shows another way to concentrate scheelite. After grinding, ore is separated with a jig, spiral or cyclone depending of particle size. Concentrate is separated in two products: coarse particles and fines. Coarse particles are reground and fines are floated to remove sulfides. Tail of sulfide is concentrated with tables for coarser particles and with scheelite flotation for fines. These two last methods give a final scheelite concentrate.

Flowsheet 3 (Figure 10) shows a general way to concentrate scheelite when using only flotation. After grinding, flotation is used to remove sulfide. Then, tail is floated to concentrate scheelite. Classical flotation of scheelite uses a fatty acid like oleic acid as collector, sodium silicate as a modifying agent to suppress silicate flotation and sodium

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carbonate to regulate the pH to about 10. Because flotation only gives a low-grade concentrate, chemical processes are used to produce high-grade synthetic scheelite concentrate.

Recovery of scheelite is between 50 to 90%, generally 60 to 85%. Losses are due to slimes. Scheelite is a very friable mineral and attention must be paid not to overgrind it. Grade of concentrate produced by gravity separation and sulfide flotation is between 60 to 75% W03. For scheelite flotation, grade is usually from 10 to 25% W03, but some sources claim to produce concentrate with 65% W by use of paraffin oil [2]. By chemical processes, a commercially synthetic scheelite concentrate of about 65 % WO3 can be produced.

Examples of flowsheets are presented in Appendix A.

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Feed

Crushing

Grinding

Concentrate • Coarse: jigging, grinding, tabling Gravitationnal Sulfide flotation Medium: spirals, tabling t separation Fine: cyclones, tabling Tail Optional Tail V T Magnetic separation Scheelite flotation (optional)

Non-magnetic V Scheelite concentrate Scheelite concentrate

Figure 8: General flowsheet 1

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Feed

Crushing

Grinding

Gravitationnal Jig, spiral, cyclone separation

Sulfide flotation

Tail + •

• Gravitationnal Tables Scheelite flotation separation

Scheelite concentrate

Figure 9: General flowsheet 2

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Feed

Crushing

Grinding

V Sulfide flotation

tails

Scheelite flotation

Leaching

Synthetic scheelite concentrate

Figure 10: General flowsheet 3

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5 REFERENCES

1- N Krishna Rao. Benification of tungsten ores in India : A review, Bull. Mater. Sci., Vol. 19, No 2, April 1996, pp. 201-265.

2- Agar. Scheelite flotation process, Unites States Patent, Dec. 18, 1984, 4 488 959.

3- www.infomine.com/minesite/minesite.asp?site=cantung

4- N.L. Weiss, Ed. SME mineral processing handbook, vol. 2, Society of Mining Engineers, American institute of mining, metallurgical and petroleum engineers inc., New York, 1985.

5- J.N. Greaves. Tungsten and gold recovery from Alaskan scheelite-bearing ores, Report of investigations / United States Department of the Interior, Bureau of Mines ; 9251.

6- Mineral processing flowsheets, Denver equipment company, first print, U.S.A, 1962.

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APPENDIX A: Flowsheets from litterature

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GOLO TAILS

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yTAIL

A NET IC 9EïpARAYÈ

N. MAO.

REJECTS ~►CHEELiTifi CONCENTRATE~

Figure Al: Flowsheet for recovery of scheelite from KGF gold tailing in India [1]

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4~R G0t,$ F gout REWVERY ~~VIERY a-----~=•-T--~somEet.i~ •~~ ~T~ ~

Figure A2: Flowsheet for recovery of scheelite from Hutti gold ore in India [1]

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2000 9ram5 sFEEO.

$0% Solids: 7 min it~ ~. 7g. .f kg Ka 2'0:13 0_t5g1 kg dadécyimercopon

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4 min, t21re: c06 3.2 gi'Jt Ma2SâC13 E`OND17f014 1 0.2 gi1sg KA-2 law)' 0.3 gr Mg- fuel ,~tl~ (II:

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1 m~,.1:~ ütre`,celÇ CCJC1`ION'2 j 2 gfkg if~s~.2~ii#~

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1 Min , Iifre. cett ,S /Min air 2nd a, TAILS" 414+1,09 Towlroth' 25G W CLEANER

W C NCENTRATE

Figure A3: Flowsheets from tests of reference 2

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2Q00 grartm FEED

54:% Solids ? niinlllçg , 7g, r No, 2033 0.26 g tkg dodetylnercaptar

1 Tir, litre cell; O.a4 9 g !plDW Z50.: 0,15 g /kg weàsod e.

6'min;, 41, tit,re PI! ,15 I hinin; air OVT.5 ga"k.g ' Dcikatretih' Z50 amin

'Lain , 4,4 lure 0,020 kg Guar 703' 32'g Na 2.5i'D3 ~11 min 0.2,g~+ikg faiEy ~ p,3 g ikag Sunper 100 .

51ri:ïn titre. ce(t , :1,5 t ?Min.air 01 gXkg faikiy acid .E1 3 D,tS gfitp. Sunipar NO 0 3mirr.

:2. s Pate K.A-

Figure A4: Flowsheets from tests of reference 2

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Mine Crusher. ~

Sulphide Ftriéon. pram

Thicisenur.

W fiptati cn Tel!

Mar ~ flotation Packaging Con=.nhatn

Co ntrateli

Figure A5: Flowsheet of Cantung in Yukon [3]

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} Grinding : Î

-Xa ~hlate Frot e«~ Sodium SO( ide. Sulfide Taili m# Silicate Flotation Sodium. Sil loat Soap ¥Vo }Schriefit & C \ Tailings' Flotation \'Flotation Separation

mAdc

%+aC0 ¥keel Wë Age mm CAC; :Synthetic SCheëe _Pr ë ~t~ en #y: Filtrate Precipitation ,ty netiC as Sulfide so Wë £

+A Plant

k@m &ü : #era &kState

Figure A6: Flowsheet of Pine Creek, California,USA[4

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Figure A7: Flowsheet for recovery of tungsten and gold from Big Hurrah deposit, Alaska, USA [5]

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n one of the large California operations, sc heelite s reover d by flodtat he r~r g cnc trate .is deft cul ds an table coseev er i Q am ut Table tailings containing slims"uT t pesp rus ft , garnet, molybdenum and tungsten is chemically treat ï to produce synthetic scheetite , C.W04. in• flotationed section the copper is floated esa s~ahids protheuctd spe scheelite flotation section after grinding the ore to -65` mesh. all

Fiowsheet of one of the U. s producers treating a ferberite ore. Thee to thet Ddyer-Buckman► Til tons per ay endhi -200 +115micx~onsAm t7E 205 W01 n t s range is recovered by the Buckman;. OTHER DECO B TUNGSTEN BULLETIN NO. TITLE C6T B2 An Improved Method of Gravity Concentration in the Pine Si. F10-B22 Trends in Modern Flotation. G3-B13 Tungsten; Canadian and World Situation.n G3-B15 Ultra Violet Light;Prosptg for Scheelite. M4-B13 Iota Mines. M4-B29 Boulder TOoptco Mills. M4-B36 Red Rose In this flowstieet of a South African tungsten plant the Flowsheet Studies Denver Mineral Jig recovers a substantial amount of high Tungsten, Gravity grede WO, concentrate. This plant treats 110 tons of ore per Mi-P6 Concentration. dey and total WO* recovery is over 90%. Bismuth Is removed MT-P13 Tungsten-Gold, Flotation and Gravity by leaching the concentrate with nitric acid. Concentration.

Figure A8: Flowsheets from reference 6

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UIIf1ÏffI111f1111I11i '71=14, , go

This flowsheet of a small Colorado operation recovers ferber- Ito by an all gravity circuit making over 80% recovery. The Denver Mineral Jig treats the minus sixteenth Inch trammel screen undersize and Is making a 60% concentrate. Gravity concentrates are heat treated and leached to remove phosphorus. When sulfides are present a Denver finit Cell is used on e featch basis to clean up the concentrate.

This is a icai fiowsheet for tungsten ore containing little or no sulphide minerals. (loth coarse and fine jigs are used because some of the *wheelies is free and some is present as a middling in the coarser sizes. gall crushing of the coarse jig concentrate and combining it with the Denver Minorai Ji concentrate for cleaning is usually necessary. Tabling and otation recovers a high percentage of the tungsten not fa

This ail gravity flowsheet is applicable te many scl+eeiite ores whore crushing and grinding to et least 10 mesh is necessary te liberate the tungsten mineral. A 50 ton plant in Nevada recovered 94% of the tungsten when grindingto 22 mesh and producing a 60% WO: concentrate from ore containing up to 2% W05.

This 200 metric ton plant in Argentina treats a co lex are with about t/s% WO,. This plant is being moderniz d and will include several Denver Minerai Jigs plus flotation for bismuth recovery and sulfide removal.

Figure A9: Flowsheets from reference 6

COREM 1180, rue de la Minéralogie, Québec (Québec) G1N 1X7 Canada Project no. T920 le (418) 527-8211.6i (418) 527-9188 G-GEN-13 (2005-12-13)

This plant in Sweden recovered 45% of the tungsten which was formerly loot. This was accomplished by the installa= tion of the Denver -Buckman Tilting E'on- oentrator for recovery of floe acheei#flak in the slimes. This Canadian operation removes gold and sulfides from gravity seheeiite rate by leaching and flotation methods. Up to 65% of the tungsten recovered is obtained;by the Denver Mineral Jig--a product assaying 72-73% Was,

This flowsheet is adapted to concentration of tungsten ore in small tonnages. The Denver Mineral Jig plays an important Fiowsheet of a Nevada mill treating 150 tons per day scheedite role due to its ability to handle an unclassified feed, with ore, Flotation feed is all minus 65 mesh; reagents used for outstanding recovery in coarse sizes and substantial recovery. *dweller flotation are soda ash, sodium silicate, oleic acid, and of fine tungsten minerals. A selective high grads product is reagent 70e. Overall recovery of tungsten is plus 92%. obtained with minimum water. Notation concentrates are subjected to chemical treatment.

Figure A10: Flowsheets from reference 6

COREM 1180, rue de la Minéralogie, Québec (Québec) GIN 1X7 Canada Project no. T920 it (418) 527-8211 • (418) 527-9188 G-GEN-13 (2005-12-13)

This is ..a typical fIowsheet: for a tungsten ore containing en important amount of gold associated with sulphide. The Denver Minerai Jig recovers a high grade follOsienVoici product which is amalgamated and cleaned up in a batch through a Denver Unit Ceti for gold and sulfide removal. Denver "Sub-k' flotation removes the balance of the gold bearing sulfides. Tables and; the Denver-Buclnnan 1(111n Concentrator recover the fine tungsten not saved in the lig.

this fiowaheet was used in the Quebec Bureau of Mines to test tungsten ores,.

41 Thli Colorado Tungsten Mill handled are, principally forbore., on a custom basis during World War 11: Stage crushing and gravity concentration wore used. Concentrates assayed from 51 to 71% W01. Law grade ferberlte flotation concentrate was shipped to a chemical plant for extraction of tar tan.,

Figure Al 1: Flowsheets from reference 6

COREM 1180, rue de la Minéralogie, Québec (Québec) GIN 1X7 Canada Project no. T920 If (418) 527-8211 • bi (418) 527-9188 G-GEN-13 (2005-12-13)