prepared for northern graphite - ontario · primary rod grind-marcy (p 80 ~ 1,200 microns)...

SGS Canada Inc. P.O. Box 4300, 185 Concession Street, Lakefield, Ontario, Canada K0L 2H0 Tel: (705) 652-2000 Fax: (705) 652-6365 www.met.sgs.com www.ca.sgs.com

Member of the SGS Group (SGS SA)

An Investigation into

THE RECOVERY OF GRAPHITE FROM A BULK SAMPLE FROM BISSET CREEK

prepared for

NORTHERN GRAPHITE

Project 12394-02 – FINAL DRAFT – Final Report June 21, 2012

NOTE: The practice of this Company in issuing reports of this nature is to require the recipient not to publish the report or any part thereof without the written consent of SGS Minerals Services. This document is issued by the Company under its General Conditions of Service accessible at http://www.sgs.com/terms_and_conditions.htm. Attention is drawn to the limitation of liability, indemnification and jurisdiction issues defined therein. WARNING: The sample(s) to which the findings recorded herein (the 'Findings') relate was (were) drawn and / or provided by the Client or by a third party acting at the Client’s direction. The Findings constitute no warranty of the sample’s representativity of the goods and strictly relate to the sample(s). The Company accepts no liability with regard to the origin or source from which the sample(s) is/are said to be extracted. The findings report on the samples provided by the client and are not intended for commercial or contractual settlement purposes. Any unauthorized alteration, forgery or falsification of the content or appearance of this document is unlawful and offenders may be prosecuted to the fullest extent of the law. Test method information available upon request.

Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT

SGS Minerals Services

i

Table of Contents

Executive Summary .......................................................................................................................... iv

Introduction ...................................................................................................................................... iv

Testwork Summary ............................................................................................................................ 1

1. Background ............................................................................................................................... 1

2. Objectives ................................................................................................................................. 1

3. Sample Description and Ore Characterization ........................................................................... 1

4. Comminution Tests ................................................................................................................... 2

4.1. JK DropWeight Test .......................................................................................................... 2

4.2. Bond Ball Mill Grindability Test .......................................................................................... 4

4.3. Bond Abrasion Test .......................................................................................................... 5

4.4. Bond Low Energy Impact Test .......................................................................................... 6

5. Pilot Plant Testing ..................................................................................................................... 7

5.1. Pilot Plant Objectives ........................................................................................................ 7

5.2. Pilot Plant Setup and Configuration ................................................................................... 7

5.3. Start-up Conditions ......................................................................................................... 11

5.4. Methods for Evaluating Plant Performances .................................................................... 12

5.5.3. Sulphide Regrind Mill ........................................................................................... 16

5.9. Environmental Characterization of Pilot Plant Products ................................................... 28

6.1. Head Assays .................................................................................................................. 29

6.2. Batch Flotation ................................................................................................................ 30

6.3. Locked Cycle Flotation .................................................................................................... 31

7. Product Characterization and Handling .................................................................................... 39

8. Conclusions and Recommendations ........................................................................................ 39

Appendix A – Comminution Test Data

Appendix B – Pilot Plant Operation Logs

Appendix C – Variability Batch Flotation Test Data

Appendix D – Variability Locked Cycle Test Data

Appendix E – NAG and ABA Certificates



ii

List of Tables

Table 1: Head Grade of the Bisset Creek Pilot Plant Composite ........................................................ iv

Table 2: Summary of Comminution Test Results ............................................................................... iv

Table 3: Summary of Pilot Plant Mass Balances ................................................................................. i

Table 4: Size-by-Size Analysis of Final Graphite Concentrate ............................................................ ii

Table 5: Summary of Variability LCT Results .................................................................................... iii

Table 6: Size Fraction Analysis of Graphite Concentrates from LCTs ................................................ iii

Table 7: Pilot Plant Composite Head Assays of Primary Elements of Interest ..................................... 2

Table 8: Pilot Plant Composite ICP-OES Scan ................................................................................... 2

Table 9: Summary of Comminution Test Results ................................................................................ 2

Table 10: SAG/Autogenuous Mill Parameters from DW Test Results ................................................. 3

Table 11: Predicted Wear Rates ........................................................................................................ 6

Table 12: Bisset Creek Pilot Plant Equipment List .............................................................................. 9

Table 13: Metallurgical Targets ........................................................................................................ 11

Table 14: Reagent Addition Points and Dosages at Beginning of Pilot Plant Campaign .................... 12

Table 15: Primary Rod Mill Process Data ......................................................................................... 15

Table 16: Secondary Ball Mill Process Data ..................................................................................... 16

Table 17: Summary of Reagent Dosages (g/t) ................................................................................. 20

Table 18: Head Assays from Pilot Plant Surveys .............................................................................. 21

Table 19: Summary of Circuit Mass Balances .................................................................................. 23

Table 20: Size-by-Size Analysis of Final Graphite Concentrate (PP-16 and PP17) ........................... 24

Table 21: Average Total Carbon Assays (%) of Grab Samples (PP-15 to PP-17) ............................. 26

Table 22: Modified Acid-Base Accounting Test Results .................................................................... 28

Table 23: Net Acid Generating Test Results..................................................................................... 29

Table 24: Head Analysis Results of Variability Composites .............................................................. 30

Table 25: Summary of Batch Cleaner Tests on Variability Composites ............................................. 31

Table 26: Summary of Locked Cycle Mass Balances ....................................................................... 35

Table 27: Flake Size Distribution of Final Graphite Concentrates from LCTs .................................... 36

Table 28: Acid-Base Accounting Test Results for LCT Products ....................................................... 37

Table 29: Net Acid Generating Tests for LCT Products .................................................................... 38

Table 30: Summary of PAX Dosage Tests ....................................................................................... 40



iii

List of Figures

Figure 1: Bisset Creek Pilot Plant Flowsheet ...................................................................................... v

Figure 2: Frequency Distribution of A*b in the JKTech Database ........................................................ 3

Figure 3: Frequency Distribution of t10 @ 1 kWh/t in the JKTech Database ......................................... 3

Figure 4: Frequency Distribution of ta in the JKTech Database ........................................................... 4

Figure 5: Histogram of BWI Results for Bisset Creek and SGS Database........................................... 5

Figure 6: Histogram of AI Results for Bisset Creek and SGS Database .............................................. 6

Figure 7: Bisset Creek Pilot Plant Flowsheet .................................................................................... 10

Figure 8: Grab and Survey Sample Profile – Flash Flotation Feed.................................................... 14

Figure 9: Grab and Survey Sample Profile – Graphite Rougher Feed ............................................... 16

Figure 10: Grab and Survey Sample Profile - Sulphide 1st Cleaner Feed .......................................... 17

Figure 11: Grab and Survey Sample Profile – Polishing Mill #1 ........................................................ 18

Figure 12: Grab and Survey Sample Profile – Polishing Mill #2 ........................................................ 18

Figure 13: Reagent Dosages (PP-03 to PP-17) ................................................................................ 20

Figure 14: Grab Sample Profile – Graphite Concentrates (PP-15 to PP-17) ..................................... 25

Figure 15: Grab Sample Profile – Graphite Rougher and Scavenger Tailings (PP-15 to PP-17)........ 25

Figure 16: Flash and Graphite Rougher Concentrate Kinetics .......................................................... 27

Figure 17: Flash and Graphite Rougher Tailings Grades .................................................................. 27

Figure 18: Flowsheet Option I – Cycles A& B ................................................................................... 32

Figure 19: Flowsheet Option II – Cycles C & D................................................................................. 33

Figure 20: Flowsheet Option III – Cycles E & F ................................................................................ 33



iv

Executive Summary

A flotation pilot plant campaign was completed on approximately 110 tonnes of a bulk sample originating

from Northern Graphite’s Bisset Creek deposit. The pilot plant program comprised a number of objectives,

which are outlined below:

• Demonstration of the proposed flowsheet on a pilot plant scale;

• Production of concentrate and tailings for downstream testing;

• Development of engineering data to support the generation of process design criteria.

The material was received in three 40 tonne dump trucks, stage-crushed to -5/8”, and homogenized with

a front-end loader. A 100 kg sample was extracted for laboratory scale testing and as reference material.

A representative sub-sample was submitted for chemical analysis and the results are presented in Table

1.

Table 1: Head Grade of the Bisset Creek Pilot Plant Composite

A series of comminution tests was completed to support the sizing of the crushing and grinding

equipment and to quantify media wear. A summary of the results is presented in Table 2.

Table 2: Summary of Comminution Test Results

The circuit was configured based on the flowsheet that was developed on a Bisset Creek Master

composite under project number 12394-001. The pilot plant flowsheet is presented in Figure 1 including

all reagent addition points.

C(t) C(g) TOC leco CO3 S

2.50 2.40 < 0.05 0.43 1.06

Assays (%)

Sample Relative JK Parameters CWI BWI AI

Name Density A x b ta (kWh/t) (kWh/t) (g)

Northern Graphite PP Comp 2.67 109 0.75 9.4 10.3 0.307



v

Figure 1: Bisset Creek Pilot Plant Flowsheet

Feed (-5/8")

Graphite Cleaner

Tailings

Graphite

Concentrate

1st Clnr

Flotation

1stClnr

Scavenger

Flotation

Primary Rod Grind - Marcy

(P80 ~ 1,200 microns)

Secondary Ball Grind - Hendy

(P80 ~ 350-400 microns)

Polishing Grind 1

16" x 32"

Polishing Grind 2

12" x 24"

Small Derrick Screen

(SWG18-24BC60)

1,000 kg/h

30 kg/h

964 kg/h

934 kg/h

50 kg/h

884 kg/h

39 kg/h 1 kg/h

26 kg/h

27 kg/h

66 kg/h

6"

4"

D8-Tank

D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank

Large Derrick

Screen(SWG48-30BC24)

D7-Tank D7-Tank D7-Tank D7-Tank


Graphite Rougher Sulphide Rougher

Sulphide Cleaner

Flash Flotation

36 kg/h

Sulphide Rougher

Tails

Sulphide 1st Clnr

Tails

8 mesh

(80, 88,

or 90 TBC)

Sulphide Ro Regrind – 16" x 32"

(P80 ~ 100-120 microns)

Kerosene

Kerosene,

MIBCKerosene,

MIBC

Kerosene,

MIBCKerosene,

MIBC

Kerosene,

MIBCKerosene,

MIBC

PAX,

MIBC

PAX,

MIBC

PAX,

MIBC

PAX,

MIBC

PAX, MIBC

PAX,

MIBC

Kerosene,

MIBC

Kerosene,

MIBC

Kerosene

Kerosene

Kerosene

M

Sulphide 1st Clnr

Concentrate

Mags

Effluent Tails

(in Super Sacs)

Magnetic

Separation

Tailings

Thickener

Belt Filter

25 kg/h

25 kg/h

Dewatering

Screen

Dewatering

Screen

`

Graphite Mechanical Scavenger

KeroseneKerosene

D8-Tank D8-Tank D8-Tank

Flash Flotation



i

The pilot plant was operated for 17 shifts. Due to a series of mechanical and metallurgical challenges, the

circuit was only optimized at the end of PP-14. An extended run commenced on PP-15 and five

successful surveys were completed during PP-16 and PP-17, which consisted of multiple cuts of each

stream of the flotation circuit. The direct head assays of each product were then used with data

reconciliation software BILMATTM

to generate a circuit mass balance. A summary of the five pilot plant

mass balances is presented in Table 3. The graphite recoveries into the final concentrate ranged between

90.5% in survey PP-17B and 94.9% in survey PP-16C. The adjusted concentrate grades varied from

93.2% in PP-16C to 95.3% in PP-16A.

Table 3: Summary of Pilot Plant Mass Balances

C(t) S(%) C S

Final Graphite Conc 2.3 95.3 0.04 92.1 0.1

Graphite 1st Clnr Conc Screen O/S 1.3 94.1 0.05 53.2 0.1

4" Column O/F 1.0 97.0 0.02 39.0 0.0

Sulphide 1st Clnr Conc 1.9 1.93 28.0 1.5 48.0

Mags 0.7 0.14 33.0 0.0 22.1

Non-Mags 95.1 0.16 0.34 6.4 29.9

Feed 100.0 2.43 1.08 100.0 100.0



4" Column O/F 0.2 85.1 0.01 6.6 0.0


Mags 0.2 0.12 30.2 0.0 4.8

Non-Mags 95.6 0.11 0.57 4.2 53.5

Feed 100.0 2.38 1.01 100.0 100.0



4" Column O/F 1.0 96.8 0.01 42.1 0.0


Mags 0.1 0.10 30.2 0.0 4.2

Non-Mags 95.7 0.08 0.57 3.4 54.1

Feed 100.0 2.35 1.01 100.0 100.0



4" Column O/F 0.9 97.1 0.02 35.0 0.0


Mags 1.0 0.16 31.4 0.1 27.2

Non-Mags 94.8 0.18 0.32 7.2 27.1

Feed 100.0 2.38 1.12 100.0 100.0



4" Column O/F 0.3 96.7 0.01 10.2 0.0


Mags 1.2 0.11 30.5 0.0 27.3

Non-Mags 94.6 0.24 0.42 8.4 30.7

Feed 100.0 2.74 1.29 100.0 100.0

Grade % Distribution

PP-17A

PP-17B

Wt %Survey

PP-16A

PP-16B

PP-16C

Product



ii

Since the revenue for the graphite concentrate is highly dependent on the flake size distribution and the

grade of each size fraction, the final concentrate from each survey was subjected to a size fraction

analysis. The results of this analysis are presented in Table 4 and reveal that almost 50% of the

concentrate mass consisted of +48 mesh flakes, which are considered a premium product.

Table 4: Size-by-Size Analysis of Final Graphite Concentrate

At the end of the program a series of batch and locked cycle tests were completed on eight composites

from low-grade to high-grade zones within the Bisset Creek deposit. The mass recovery, graphite

recovery, and concentrate grade of the eight LCTs are presented in Table 5 and reveal high graphite

recovery of 95.2% to 99.1% into the final concentrate at grades of 93.5% C to 96.5% C. The data from

the size fraction analysis of the concentrates from these LCTs are provided in Table 6 and confirm the

coarse flake size distribution of the pilot plant. The +48 mesh fraction ranged between 43.1% and 58.5%

by mass compared to 45.7% to 49.8% in the pilot plant

Selected samples from the locked cycle tests were submitted for a basic environmental analysis to

determine the most suitable flowsheet option to produce a large percentage of non-acid generating

tailings and only a small tailings stream of acid generating material that requires special tailings handling.

A sulphide rougher and cleaner circuit in combination with a magnetic separator that treats the combined

sulphide rougher and 1st cleaner tailings produced non-acid generating tailings with the lowest mass

recovery into the high-sulphur tailings stream.

In conclusion, the Bisset Creek pilot plant campaign demonstrated the suitability of the proposed

flowsheet despite concerns that the bulk sample was partly weathered. As a result of this partial

weathering and the lack of operating time to optimize the circuit, the metallurgical performance of the pilot

plant was slightly inferior compared to the laboratory program that was completed on a Master composite

and eight variability composites.

Mesh µm

48 300 49.1 97.7 49.8 49.9 95.1 49.8 49.2 92.7 48.7 48.2 94.4 48.0 45.4 95.4 45.7

65 212 19.6 93.6 19.0 19.3 93.5 19.0 20.8 91.8 20.4 20.6 94.3 20.5 20.2 94.2 20.1

80 180 8.0 97.9 8.1 7.6 96.2 7.7 8.0 97.3 8.3 8.4 96.0 8.5 8.7 97.9 9.0

100 150 5.0 97.8 5.1 4.6 97.8 4.8 4.4 97.5 4.6 4.9 96.7 5.0 5.2 96.8 5.3

150 106 7.8 97.6 7.9 7.3 98.5 7.5 6.2 99.3 6.6 7.3 98.0 7.5 8.5 96.6 8.7

Pan -106 10.5 93.1 10.1 11.3 94.5 11.2 11.4 93.9 11.4 10.7 92.3 10.4 12.0 89.6 11.3

96.4 100.0 95.2 100.0 93.6 100.0 94.8 100.0 100.0 94.9 100.0

SizeGrade

% C(t)

Grade

% C(t)

Grade

% C(t)

Distr.

(%) C(t)

Distr.

(%) C(t)

Distr.

(%) C(t)

PP-16A PP-16B PP-16C PP-17A PP-17B

Total

P80 in µm

Grade

% C(t)

Grade

% C(t)

Ret.

%

Ret.

%

Ret.

%

Ret.

%

Ret.

%

374378379380379

Distr.

(%) C(t)

Distr.

(%) C(t)



iii

Table 5: Summary of Variability LCT Results

Table 6: Size Fraction Analysis of Graphite Concentrates from LCTs

Assay (%) Distribution (%)

% C(t,g) C(t,g)

Final Concentrate 1.4 93.5 96.8

Head (calc) 100.0 1.38 100.0Head (direct) 1.22


Head (calc) 100.0 1.35 100.0

Head (direct) 1.45Final Concentrate 1.6 96.5 97.7

Head (calc) 100.0 1.60 100.0

Head (direct) 1.47

Final Concentrate 1.6 95.4 96.8Head (calc) 100.0 1.58 100.0

Head (direct) 1.30




Head (calc) 100.0 3.66 100.0

Head (direct) 3.34Final Concentrate 2.6 95.3 97.1

Head (calc) 100.0 2.56 100.0

Head (direct) 2.32



LCT HG-4

LCT LG-3

LCT LG-4

LCT MG-2

LCT MG-4

LCT HG-1

LCT HG-2

LCT HG-3

Test ProductWeight

+32 +48 +80 +100 +200 -200 >80

LG Pit #3 19.0 32.8 23.2 5.0 10.4 9.5 75.1

LG Pit #4 22.6 32.6 20.1 4.6 9.5 10.5 75.3

MG Pit #2 23.7 34.1 22.1 3.9 8.7 7.5 79.9

MG Pit #4 25.7 32.8 19.9 3.8 9.3 8.4 78.4

HG Pit #1 11.2 31.9 28.1 7.0 12.8 9.0 71.2

HG Pit #2 14.8 32.8 25.9 5.9 12.0 8.6 73.5

HG Pit #3 20.2 35.1 22.7 5.3 9.3 7.4 78.0

HG Pit #4 15.7 32.0 24.4 6.0 11.7 10.2 72.1

Minimum 11.2 31.9 19.9 3.8 8.7 7.4 71.2

Maximum 25.7 35.1 28.1 7.0 12.8 10.5 79.9

Average 19.1 33.0 23.3 5.2 10.5 8.9 75.4

StdDev 4.9 1.1 2.8 1.1 1.5 1.2 3.1

Rel StdDev 25.8 3.3 12.0 21.4 14.3 13.0 4.1

Composite

Flake Size Distribution - % retained (mesh)



iv

Introduction

A lab program was completed in 2010/2011 on a Master composite originating from the Bisset Creek

deposit. This lab program generated a flowsheet and reagent conditions that were deemed suitable to

produce a graphite concentrate grading at least 95% C and to maximize overall graphite recovery. In

order to demonstrate the suitability of this proposed flowsheet on a larger scale and continuous operation,

a decision was made to proceed with pilot scale testing.

A shipment comprising approximately 110 tonnes of a bulk composite of the Bisset Creek mineralization

arrived at the SGS Lakefield site in early September 2011 and sample preparation work commenced

immediately. The setup of the pilot plant was completed in late October and the circuit was commissioned

during the second week in November. Over the course of the following four weeks, the circuit was

operated for 17 shifts until December 8, 2012.

The results were communicated to Don Baxter of Northern Graphite, their engineering company G-

Mining, and SGS Geostat as they became available. Representatives of the three companies were

present on-site throughout the four weeks of operation.

__________________________ Oliver Peters, M.Sc., P.Eng, MBA Associate Metallurgist ______________________ Dan Imeson, M.Sc Manager, Mineral Processing Experimental work by: Pilot Plant Crew, Kevin Stewart Report preparation by: Su Mckenzie Reviewed by:



1

Testwork Summary

1. Background

Northern Graphite’s Bisset Creek deposit is located in northern Ontario close to the town of Mattawa. The

deposit grades about 2.5 – 3.0 % graphitic carbon, which is present predominantly as large flakes greater

than 48 mesh. A flowsheet was developed at SGS in 2010 – 2011, which maximizes the recovery of

graphite while minimizing flake breakage. In order to demonstrate this process on a larger scale for a

bankable feasibility study, a 110 tonne bulk sample from the Bisset Creek deposit was received at the

SGS Lakefield site for pilot scale testing. The pilot plant was setup in October 2011 and was operated in

November and December 2011 at a feed rate of approximately 1 tonne/hour.

2. Objectives

The pilot plant program comprised a number of objectives, which are outlined below:

• Demonstration of the proposed flowsheet on a pilot plant scale;

• Production of concentrate and tailings for downstream testing;

• Development of engineering data to support the generation of process design criteria.

3. Sample Description and Ore Characterization

A shipment comprising approximately 110 tonnes of the Bisset Creek bulk sample was received at the

SGS Lakefield site on September 6, 2012 and September 7, 2012. The sample arrived in three dump

trucks that were loaded on site from a stock pile of ore that was blasted shortly before the bulk sample

was collected.

Prior to any sample preparation work, 150 kg of rocks between 4” and 8” were randomly selected from

the stockpile for grindability tests. These rocks were then prepared as required by the specific

comminution test.

The remaining sample was stage crushed to -5/8” and then blended with a front-end loader on a clean

concrete pad. Once the sample was blended a 100 kg sub-sample was extracted for bench-scale

validation testing and as reference material. This sub-sample was stage-crushed to -10 mesh before it

was split into 2 kg and 1 kg test charges. At this point a sub-sample was extracted for head analysis.

The results of the chemical analysis of the primary elements of interest and anICP-OES scan are

presented in Table 7 to Table 8, respectively.



2

Table 7: Pilot Plant Composite Head Assays of Primary Elements of Interest

Table 8: Pilot Plant Composite ICP-OES Scan

4. Comminution Tests

A series of comminution tests was completed on the Bisset Creek pilot plant composite to support the

sizing of the crushing and grinding equipment and to quantify media wear. A summary of the results is

presented in Table 9.

Table 9: Summary of Comminution Test Results

4.1. JK DropWeight Test

The JKTech drop-weight test provides ore specific parameters that are combined with equipment

detailings and operating conditions to analyze and/or predict SAG/autogenuous mill performance. The

SAG/autogenuous mill parameters from the DW test results for the Bisset Creek sample are presented in

Table 10. In order to compare the Bisset Creek material with other samples tested by JKTech, the

frequency distribution of the parameters A*b and t10 @ 1kWh/t from the JKTech database of ores are

presented in Figure 2 and Figure 3, respectively. Further, the frequency distribution of the ta parameter

from the JKTech database of samples is plotted in Figure 4.

C(t) C(g) TOC leco CO3 S

2.50 2.40 < 0.05 0.43 1.06

Assays (%)

Ag Al As Ba Be Bi Ca Cd Co Cr Cu

< 2 43,400 < 30 416 1.14 < 20 25,300 < 2 < 20 144 55

Fe K Li Mg Mn Mo Na Ni P Pb Sb

24,400 19,400 < 5 12,600 1,210 13 9,970 60 1,040 < 20 < 10

Se Sn Sr Ti Tl U V Y Zn

< 30 < 20 116 1,950 < 30 < 20 139 17.9 98

Assays (g/t)

Sample Relative JK Parameters CWI BWI AI

Name Density A x b ta (kWh/t) (kWh/t) (g)

Northern Graphite PP Comp 2.67 109 0.75 9.4 10.3 0.307



3

Table 10: SAG/Autogenuous Mill Parameters from DW Test Results

Figure 2: Frequency Distribution of A*b in the JKTech Database

Figure 3: Frequency Distribution of t10 @ 1 kWh/t in the JKTech Database



4

Figure 4: Frequency Distribution of ta in the JKTech Database

The Bisset Creek pilot plant composite produced a A*b value of 108.5, which placed it into the soft range

of resistance to impact breakage. In the JKTech database, 87% of the almost 3,000 samples tested have

lower A*b values. With a ta of 0.75, the Bisset Creek composite fell into the soft abrasion range compared

to the other samples tested by JKTech. Almost 75% of these other samples produced lower ta values.

The full report of the JKTech DW test results is included in Appendix A.

4.2. Bond Ball Mill Grindability Test

A Bond ball mill grindability test was completed on the Bisset Creek pilot plant composite to determine the

grinding energy that is required in a ball mill. The Bond Work Index (BWI) of 10.3 kWh/t places the Bisset

Creek sample into the soft range of BWI values as evidenced in Figure 5, which presents the histogram of

BWI test results in the SGS database together with the Bisset Creek test results. Note that the majority of

those BWI tests were completed at a mesh of grind of 100 or 150 mesh compared to 35 mesh for the

Bisset Creek sample, which makes a comparison more difficult. The coarser screen size was selected as

the proposed Bisset Creek flotation circuit uses a relatively coarse grind size of P80 of approximately 250

microns in the graphite rougher stage. The complete BWI test results are presented in Appendix A.



5

Figure 5: Histogram of BWI Results for Bisset Creek and SGS Database

4.3. Bond Abrasion Test

A Bond abrasion test was completed on the Bisset Creek pilot plant composite to facilitate the estimation

of the grinding media and liner wear in the ball mill prior to the graphite rougher flotation. The abrasion

index of 0.307 places the Bisset Creek material into the range of medium abrasivity. Only 40% of the over

2,000 samples tested at SGS Lakefield yielded a higher abrasion index, which is also illustrated in the

histogram shown in Figure 6.

The predicted wear rates for the different grinding media and liners are presented in Table 11 and the

complete test results are included in Appendix A.

0

10

20

30

40

50

60

70

80

90

100

0

200

400

600

800

1000

1200

1400

1600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 >28

Cu

mu

lati

ve F

req

uen

cy (

%)

Fre

qu

en

cy

Bond Ball Mill Work Index - Metric

Database

Bisset Creek



6

Figure 6: Histogram of AI Results for Bisset Creek and SGS Database

Table 11: Predicted Wear Rates

4.4. Bond Low Energy Impact Test

A Bond low energy impact test was completed on the rock samples of the Bisset Creek pilot plant

composite. The test determines the Bond Impact Work Index (CWi), which can be used with Bond’s Third

Theory of Comminution to calculate net power requirements for sizing crushers. It can also be used to

determine the required open-side settings for jaw and gyratory crushers or closed-side settings for cone

0

10

20

30

40

50

60

70

80

90

100

0

50

100

150

200

250

300

350

400

450

500

0.0

5

0.1

5

0.2

5

0.3

5

0.4

5

0.5

5

0.6

5

0.7

5

0.8

5

0.9

5

1.0

5

1.1

5

1.2

5

1.3

5

>1.4

0

Cu

mu

lati

ve F

req

uen

cy (

%)

Fre

qu

en

cy

Abrasion Index

Database

Bisset Creek

lb/kwh kg/kwh

Wet rod mill, rods: 0.35*(Ai-0.020) 0.20 0.27 0.12

Wet rod mill, liners: 0.035*(Ai-0.015) 0.30 0.024 0.011

Ball Mill (overflow and grate discharge types)

Wet ball mill, balls: 0.35*(Ai-0.015) 0.33 0.23 0.11

Wet ball mill, liners: 0.026*(Ai-0.015) 0.30 0.018 0.008

Ball Mill (grate discharge type)

Dry ball mill, balls: 0.05*(Ai) 0.50 0.028 0.013

Dry ball mill, liners: 0.005*(Ai) 0.50 0.0028 0.0013

Crushers (gyratory, jaw, cone)

Crusher, liners: (Ai+0.22)/11 0.048 0.022

Roll crusher, shells: (Ai/10)0.67 0.097 0.044



7

crushers for a given product size. The CWi for the Bisset Creek composite was 9.37 kWh/t and a report

with complete test detailings is included in Appendix A.

5. Pilot Plant Testing

A pilot plant program was conducted on approximately 110 tonnes of a Bisset Creek bulk composite. The

following sections discuss the pilot plant objectives, setup, operating conditions and metallurgical results.

All pilot plant detailings are provided in Appendix B.

5.1. Pilot Plant Objectives

The primary objectives of the pilot plant campaign were to:

• Evaluate the flotation response of the proposed Bisset Creek flowsheet under continuous operating conditions;

• Reduce the sulphur content in the tailings to generate a non-acid generating waste stream. The majority of the S units would be recovered into a high S grade product stream with a relatively low mass recovery that would be disposed of in a separate area;

• Produce concentrate and tailings for downstream testing;

• Generate data to support engineering design.

5.2. Pilot Plant Setup and Configuration

The ore was treated in the flowsheet that is presented in Figure 7 using the equipment shown in Table 12.

Ore, which was stage-crushed to -5/8” and thoroughly blended prior to the pilot plant campaign, was

subjected to a primary grind in a rod mill with a grind size target of P80 = 700 to 800 microns. The rod mill

discharge was classified on a 48” Kason vibrating screen with a 2,380 microns (8 mesh) screen deck and

the oversize was circulated back to the mill feed. The screen undersize was transferred to a bank of four

flash flotation cells. The primary purpose of the flash flotation stage was the recovery of coarse graphite

flakes. The only reagents that were used in this stage and the entire graphite circuit were kerosene or fuel

oil as the graphite collector and methyl isobutyl carbinol (MIBC) as the frother. The entire Bisset Creek

circuit was operated at natural pH, which eliminated the need for any pH modifiers such as lime or acid.

The flash flotation tailings were fed onto the secondary ball mill classification screen, which was targeting

a product size of P80 ~ 300 microns. Any oversize was redirected into a Hendy ball mill that was operated

in closed circuit with the secondary ball mill classification screen. The screen undersize was introduced

into the graphite rougher stage and the rougher tailings were forwarded to the sulphide circuit. The

primary purpose of the graphite rougher stage was to recover any graphite flakes that were liberated in

secondary grinding.

The flash and graphite rougher concentrates were combined and fed onto a dewatering screen with an

aperture size of 125 microns (120 mesh) that was added to maintain an acceptable density in the

polishing mill #1. The polishing mill #1 was charged with ceramic grinding media in order to liberate the

graphite flakes from any impurities. The mill discharge was combined with the dewatering screen



8

undersize and introduced into two 6” flotation columns that were operated in parallel. Due to the low

stage-recoveries associated with flotation columns, the column tailings were processed in a graphite

mechanical scavenger to recover the majority of the graphite units that reported to the column tailings.

The 6” column concentrate was classified at approximately 60 mesh or 250 microns. The screen oversize

represented a final graphite concentrate, while the screen undersize was directed onto a second

dewatering screen. The screen oversize was treated in polishing mill #2 to further improve the liberation

of the graphite flakes as the 60 mesh size fraction yielded a lower degree of liberation. The mill discharge

was pumped together with the dewatering screen undersize into a single 4” flotation column, which acted

as 1st cleaner scavenger. The concentrate of this column was combined with the +60 mesh concentrate to

form the combined graphite concentrate. The 4” column tailings were transferred into the graphite

mechanical scavenger stage. The concentrate from these mechanical flotation cells were returned to the

feed end of the graphite cleaning circuit, while the tailings were combined with the tailings of the sulphide

circuit.

The sulphide removal circuit, which treated the graphite rougher tailings, was incorporated to remove the

majority of the sulphides from the process tailings stream. This approach would concentrate the acid-

generating sulphide minerals into a product with a low mass recovery, while the majority of the tailings

would be non-acid generating and could be disposed of in a tailings facility without special lining. The

sulphide circuit consisted of a sulphide rougher, regrind mill, and a sulphide 1st cleaner stage. The

collector in the sulphide circuit was Potassium Amyl Xanthate (PAX) and MIBC was used as the frother.

The sulphide rougher and 1st cleaner tailings were combined and then processed together with the

graphite mechanical scavenger tailings in a magnetic separator to remove any slow floating, magnetic

sulphide minerals such as monoclinic pyrrhotite. The magnetic separation tailings were treated in a

thickener followed by a belt filter to dewater the tailings and placed into super sacs. The magnetic

separation concentrate was collected separately, but in the commercial process this product would be

combined with sulphide 1st cleaner concentrate.



9

Table 12: Bisset Creek Pilot Plant Equipment List

ID Item Specifications Notes

1 Hopper 2.5 t Hopper Feed hopper with variable speed belt feeder

2 Primary Mill 2' x 4' Marcy Rod Mill Media charge = rods

3 Primary Mill Screen 48" Kason 8 mesh deck 2 Kason screens operating in parallel, 8 mesh

4 Flash Flotation 4 x D8 1 bank of 4 x D8 (tank cell)

5 Secondary Mill Hendy Mill Media charge = balls

6 Secondary Mill Screen Large Derrick SWG48-30BC24

7 Graphite Rougher 8 x D8 2 banks of 4 x D8 (Tank type)

8 Sulphide Rougher 8 x D8 2 banks of 4 x D8 (Tank type)

9 Dewatering Screen - Polishing Grind 1 24" Kason 120 mesh (125 microns)

10 Polishing Grind 1 16" x 32" Denver Media charge = ceramic grinding media

11 1st Clnr Flotation 6" Column(s) Two columns in parallel

12 1st Clnr Concentrate Screen Small Derrick SWG18-24BC60

13 Dewatering Screen - Polishing Grind 2 24" Kason 120 mesh (125 microns)

14 Polishing Grind 2 12" x 24" Denver Media charge = ceramic grinding media

15 1st Clnr Scavenger Flotation 4" Column(s) Two columns installed - one on stand-by

16 Graphite Mechanical Scavenger 4 x D7 1 bank of 4 x D7 (sub-A type)

17 Sulphide Rougher Concentrate Regrind Mill 16" x 32" Denver Media charge = balls

18 Sulphide Rougher Conc Mill Screen 48" Kason 80, 88, or 90 TBC

19 Sulphide 1st Cleaner 4 x D7 1 bank of 6 x D7 (Sub-A type)

20 Magentic Separator 750 Gauss Eriez

21 Tailings Thickener 7.5 ft Sala

22 Belt Filter



10

Figure 7: Bisset Creek Pilot Plant Flowsheet

Feed (-5/8")

Graphite Cleaner

Tailings

Graphite

Concentrate

1st Clnr

Flotation

1stClnr

Scavenger

Flotation

Primary Rod Grind - Marcy

(P80 ~ 1,200 microns)

Secondary Ball Grind - Hendy

(P80 ~ 350-400 microns)

Polishing Grind 1

16" x 32"

Polishing Grind 2

12" x 24"

Small Derrick Screen

(SWG18-24BC60)

1,000 kg/h

30 kg/h

964 kg/h

934 kg/h

50 kg/h

884 kg/h

39 kg/h 1 kg/h

26 kg/h

27 kg/h

66 kg/h

6"

4"

D8-Tank

D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank D8-Tank

Large Derrick

Screen(SWG48-30BC24)



Graphite Rougher Sulphide Rougher

Sulphide Cleaner

Flash Flotation

36 kg/h

Sulphide Rougher

Tails

Sulphide 1st Clnr

Tails

8 mesh

(80, 88, or 90

TBC)

Sulphide Ro Regrind – 16" x 32"

(P80 ~ 100-120 microns)

Kerosene

Kerosene,

MIBCKerosene,

MIBC

Kerosene,

MIBCKerosene,

MIBC

Kerosene,

MIBCKerosene,MIBC

PAX,MIBC

PAX,MIBC

PAX,

MIBC

PAX,

MIBC

PAX, MIBC

PAX,

MIBC

Kerosene,

MIBC

Kerosene,

MIBC

Kerosene

Kerosene

Kerosene

M

Sulphide 1stClnr

Concentrate

Mags

Effluent Tails

(in Super Sacs)

Magnetic Separation

Tailings

Thickener

Belt Filter

25 kg/h

25 kg/h

Dewatering

Screen

Dewatering

Screen

`

Graphite Mechanical Scavenger

KeroseneKerosene

D8-Tank D8-Tank D8-Tank

Flash Flotation

Northern Graphite – Bisset Creek – 12394-002


11

5.3. Start-up Conditions

The results from the laboratory scale tests carried out under 12394-001 were used to identify suitable

start-up conditions for the pilot plant in terms of grind targets, reagent dosages, and reagent addition

points.

The primary and secondary grind size targets were established at P80 = 750-800 microns and P80 ~ 300

microns. The energy input in the small lab Denver flotation cells is much higher on a per volume basis

and it was uncertain at the beginning of the pilot plant operation whether or not the coarse grind size

target for the flash flotation stage could be maintained without sanding out the flash flotation cells.

The metallurgical targets and initial reagent dosages at the beginning of the pilot plant campaign are

presented in Table 13 and Table 14, respectively. While the reagent dosages were primarily chosen

based on the LCT-1 conditions, the experience from past pilot plants was taken into account as well and

necessary adjustments were made to account for the different scale of equipment.

Table 13: Metallurgical Targets

ProductGrade Target

% C (t)

Grahite Rougher Tails < 0.20

Small Derrick Screen O/S > 95.0

4" Column O/F > 95.0

6" Column Tails < 25.0

4" Column Tails < 5.0



12

Table 14: Reagent Addition Points and Dosages at Beginning of Pilot Plant Campaign

5.4. Methods for Evaluating Plant Performances

Seventeen pilot plant runs, PP-01 to PP-17, were carried out using approximately 110 tonnes of a Bisset

Creek bulk composite. The initial commissioning run, PP-01, was completed on November 8, 2011. Due

to difficulties with the feed delivery system, no circuit samples were collected during this run. The

following day the plant was operated for approximately 7 hours under PP-02. The objectives of PP-02

Addition Point Reagent Strength Rate Dosage

% mL/min g/t

PrimaryRodMill Kerosene 1.0 7.5 4.4

Flash Flotation Cell #1 Kerosene 1.0 2.5 1.5

MIBC 1.0 10.0 5.9

Flash Flotation Cell #3 Kerosene 1.0 2.5 1.5

MIBC 1.0 5.0 3.0

Secondary BallMill Kerosene 1.0 5.0 3.0

Graphite Rougher Cell #1 Kerosene 1.0 5.0 3.0

MIBC 1.0 5.0 3.0


MIBC 1.0 5.0 3.0


MIBC 1.0 5.0 3.0


MIBC 1.0 5.0 3.0

Sulphide Rougher Cell #1 PAX 5.0 16.7 49.5

MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0

Sulphide Cleaner Cell #1 PAX 5.0 8.3 24.6

MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0


MIBC 1.0 0.0 0.0

PolishingGrind#1 Kerosene 1.0 2.3 1.4

6" Column #1 Feed Kerosene 1.0 0.7 0.4

MIBC 1.0 3.4 2.0

PolishingGrind#2 Kerosene 1.0 6.4 3.8

4" Column #1 Feed Kerosene 1.0 0.0 0.0

MIBC 1.0 18.1 10.7

Totals g/t

Kerosene 23

MIBC 33

PAX 210



13

were to ensure there were no obvious mechanical issues, to fill the mills and flotation cells with pulp, and

to establish basic metallurgy. However, mechanical and metallurgical challenges resulted in several days

of commissioning. A number of the key issues are listed below:

• Partially weathered bulk sample resulted in different flotation response;

• Coarse flash and graphite rougher flotation feed resulted in sanding of the cells;

• Polishing mill feed required dewatering to maintain an acceptable solids concentration in the

mills. As a result the finer material was not subjected to a polishing grind, which would have likely

improved liberation of those particles.

Kinetics or complete circuit surveys were performed 14 times throughout the pilot plant campaign. The

primary purpose of the surveys conducted in the earlier part of the campaign was to develop an

understanding of the circuit and to assist in making the necessary adjustments to achieve the desired

metallurgical results. The last 5 circuit surveys during PP-16 to PP-17 were completed to generate mass

balance data that could be used in the engineering study.

A total of up to 28 streams were sampled 5 times over the course of a one hour sampling period.

Assaying and sizing were completed on the various products. All products were assayed for C(t) and S

and the products with a lower graphite content were also assayed for C(g). Mass balances were

calculated using the data reconciliation software BilmatTM

to make minor adjustments to the actual assays

while attributing balanced masses to each stream.

Grab assays were collected of different product streams throughout the campaign. These grab samples

were taken every hour and submitted for C(t) and S assays. Assay turnaround times were typically less

than 1 hour for rapid evaluation of performance.

In addition, sizing was performed around the primary and secondary grinding circuits, the Derrick screen

in the graphite cleaning circuit, and the sulphide regrind circuit. The size analysis was to ensure the grind

conditions were met and served as indicators of potential problems arising in the pilot plant.

5.5. Grinding Circuit

5.5.1. Primary Rod Mill Grind

The primary grinding consisted of a 610 mm x 1,220 mm Marcy rod mill circuit operated in closed circuit

with a Kason vibrating screen. Feed material, which was crushed to -5/8” and thoroughly blended prior to

the pilot plant campaign, was loaded into a 2.5 tonne capacity feed hopper. A manually controlled

vibratory conveyor delivered the ore to the Marcy rod mill at a dry solid feed rate of approximately 1,000

kg per hour. The rod mill discharge was classified on a 2,380 microns (8 mesh) screen and the undersize

was directed to the flash flotation circuit while the oversize was returned to the rod mill.

In order to ensure that the grinding circuit was operating at target, grab and survey samples of the

primary mill screen U/S were collected and sized regularly throughout the campaign. A summary of the



14

sizing results is presented in Figure 8. The average value of all flash flotation feed samples was P80 = 767

microns with a relative standard deviation of 7.7%.

Figure 8: Grab and Survey Sample Profile – Flash Flotation Feed

A summary of pertinent primary rod mill grinding circuit process data for the last four shifts of operation is

shown in Table 15. These data were chosen as the circuit was operating more stably towards the end of

the pilot plant campaign and, therefore, produced more reliable process data during that time period. The

average flash flotation feed P80 and calculated Bond rod mill work index over this time period were 758

µm and 10.6 kWh/t respectively.

400

450

500

550

600

650

700

750

800

850

900

950

1000

PP

-02

PP

-03

PP

-04

PP

-06

PP

-07

PP

-08

PP

-09

PP

-10

PP

-12

PP

-13

PP

-14

PP

-15

PP

-16

PP

-17

P80

Fe

ed

Siz

e (

mic

ron

s)

Flash Flotation Feed



15

Table 15: Primary Rod Mill Process Data

5.5.2. Secondary Ball Mill Grind

The regrind of the flash flotation tailings was performed to improve mineral liberation of the graphite

flakes. A 845 mm x 1,130 mm Hendy ball mill was used for this grinding application. Classification was

achieved on a Derrick screen that was equipped with 870 microns screen decks. The screen undersize

was directed to the graphite rougher circuit and the oversize was returned to the mill.

Again, grab and survey samples of the primary mill screen U/S were collected and sized regularly

throughout the campaign. A summary of the sizing results is presented in Figure 9. The average value of

all graphite rougher feed samples was P80 = 329 microns with a relative standard deviation of 17.4%.

Parameter Point Unit PP-14A PP-14B PP-15A PP-15B PP-16 A PP-16 B PP-16 C PP-17A PP-17B Average

Steel Charge Rod Mill kg 360 360 360 360 360 360 360 360 360 360

Feed Rate Rod Mill kg/h 953 953 785 885 916 925 907 876 876 897

Pulp Density RM Disch g/L 1,407 1,407 1,654 1,628 1,449 1,410 1,410 1,665 1,646 1,520

Net Power Rod Mill kWh/t feed 2.52 2.55 2.47 2.45 2.61 2.40 2.61 2.46 2.84 2.55

P80 RM Feed µm 9,439 9,664 7,295 8,682 10,832 9,410 9,508 7,369 9,963 9129

P80 Flash Feed µm 691 726 828 753 798 715 750 791 771 758

Work Index Ball Mill KWh/t 9.1 9.5 13.7 10.8 10.1 9.6 10.0 11.7 10.9 10.6



16

Figure 9: Grab and Survey Sample Profile – Graphite Rougher Feed

The pertinent secondary ball mill grinding circuit data is summarized in Table 16. The average P80 of the

graphite rougher feed in PP14 to PP-17 was 282 µm and the calculated Bond ball mill work index was

15.3 kWh/t.

Table 16: Secondary Ball Mill Process Data

5.5.3. Sulphide Regrind Mill

Sub-samples of the sulphide 1st cleaner feed were collected during regular operation and all surveys. The

results of the size analyses of this product are presented in Figure 10. Due to the low solids concentration

of the sulphide rougher feed, the pulp was screened to remove the majority of the water prior to

100

150

200

250

300

350

400

450

500

PP

-02

PP

-03

PP

-04

PP

-06

PP

-07

PP

-08

PP

-09

PP

-10

PP

-12

PP

-13

PP

-14

PP

-15

PP

-16

PP

-17

P80

Fe

ed

Siz

e (

mic

ron

s)

Parameter Point Unit PP-14A PP-14B PP-15A PP-15B PP-16 A PP-16 B PP-16 C PP-17A PP-17B Average

Steel Charge Ball Mill kg 400 400 400 400 400 400 400 400 400 400

Feed Rate Ball Mill kg/h 934 934 769 867 894 903 885 858 858 878

Pulp Density BM Disch g/L 1,343 1,343 1,359 1,244 1,329 1,329 1,329 1,382 1,359 1,335

Net Power Ball Mill kWh/t feed 3.21 3.06 3.08 3.08 3.01 2.99 3.00 3.07 3.02 3.06

P80 BM Feed µm 691 726 828 753 798 715 750 791 771 758

P80 BM Disch µm 216 244 343 298 206 305 289 329 312 282

Work Index Ball Mill KWh/t 10.7 12.2 20.8 16.5 9.8 16.7 15.2 18.3 17.1 15.3



17

subjecting the screen oversize to a regrind. However, as a result the mill process data could not be

compiled for this grinding application.

Figure 10: Grab and Survey Sample Profile - Sulphide 1st

Cleaner Feed

The P80 values of the polishing mill #1 and polishing mill #2 are presented in Figure 11 and Figure 12,

respectively. Since two polishing mills were operated in open circuit (i.e. without a classification of the mill

discharge), the best option to improve mineral liberation to the column feed was to gradually increase the

amount of grinding media in the mill throughout the campaign until an acceptable concentrate grade was

achieved. This gradual increase of grinding media minimizes the risk of overgrinding, thus keeping

graphite flake breakage to a minimum. The P80 of the polishing mill #1 stabilized at the start of the

extended run (PP-15 to PP-17) and the polishing mill #2 reached a constant grind size marginally earlier

during PP-14.

50

60

70

80

90

100

110

120

130

140

150

PP

-02

PP

-03

PP

-04

PP

-06

PP

-07

PP

-08

PP

-09

PP

-10

PP

-12

PP

-13

PP

-14

PP

-15

PP

-16

PP

-17

P8

0 F

ee

d S

ize

(m

icro

ns

)



18

Figure 11: Grab and Survey Sample Profile – Polishing Mill #1

Figure 12: Grab and Survey Sample Profile – Polishing Mill #2

0

100

200

300

400

500

600

700

PP

-04

PP

-06

PP

-07

PP

-08

PP

-09

PP

-10

PP

-12

PP

-13

PP

-14

PP

-15

PP

-16

PP

-17

P8

0 F

ee

d S

ize

(m

icro

ns

)

0

50

100

150

200

250

PP

-06

PP

-07

PP

-08

PP

-09

PP

-10

PP

-12

PP

-13

PP

-14

PP

-15

PP

-16

PP

-17

P8

0 F

eed

Siz

e (

mic

ron

s)



19

5.6. Reagents

The Bisset Creek pilot plant campaign used only three flotation reagents at any given point in time, which

are listed below together with their purpose:

• Kerosene – graphite collector (PP-01 to PP-04)

• Fuel oil – graphite collector (PP-05 to PP-17)

• MIBC - Methylisobutyl Carbinol – Frother

• PAX – Potassium Amyl Xanthate – Sulphide collector

The graphite collector dosage used during start-up proved insufficient due to the process challenges that

were encountered. A series of adjustments were carried out to improve the metallurgical response of the

sample. The most relevant changes are summarized below:

• Switched from kerosene to the stronger graphite collector fuel oil at the end of PP-04 as the froth

stability and graphite recovery particularly in the flash flotation circuit was low;

• Employed 100% fuel oil solution instead of an aqueous solution for selected addition points due

to high dosage requirements and better collector properties.

The average dosages of reagents that were used in the graphite flash, graphite rougher, graphite cleaner,

sulphide rougher, and sulphide cleaner circuits are compiled for each shift in Table 17 and trend lines are

plotted in Figure 13. The complete data set with all reagent addition points and dosages for the entire

campaign are included in the operation logs in Appendix B.

All reagent dosages are expressed relative to the pilot plant feed. Due to the very light froth in the flash

flotation cell and the inability to recover sufficient graphite units into the flash flotation concentrate, the

collector was changed from kerosene to fuel oil at the end of run PP-04. Even with 1% aqueous fuel oil

solutions the combined flash and graphite rougher recovery was below expectations. It was postulated

that the fuel oil was not properly dispersed in the flotation cells due to the cold river water that was used

as process water. Hence, neat fuel oil was introduced at selected reagent addition points starting in PP-

12, which improved the overall graphite recovery noticeably. Controlling pump speed for the neat fuel oil

addition rates proved challenging as only one drop per minute corresponds to a reagent addition rate of 3

g/t. As a result, the fuel oil dosages were about 10 times higher compared to the laboratory scale tests. It

is postulated that the fuel oil addition rates could be reduced noticeably. This postulation is supported by

the fact that the dosages were gradually lowered in PP-16 and PP-17 without an impact on the overall

circuit performance.

Due to the mechanical and metallurgical challenges associated with the graphite circuit, very little

attention was given to the sulphide rougher and cleaner circuit. Hence, no optimization of the PAX

dosages was carried out and, therefore, they were likely excessive based on a head grade of

approximately 1.1 % S. In fact, lower PAX dosages of less than 200 g/t in the laboratory proved sufficient



20

to recover the floatable sulphide minerals. Note that even in the lab no PAX reagent dosage optimisation

was completed due to schedule restraints and that a surplus collector dosage was chosen to ensure that

all floatable sulphide minerals were recovered.

Table 17: Summary of Reagent Dosages (g/t)

Figure 13: Reagent Dosages (PP-03 to PP-17)

PP Run Kerosene Fuel Oil MIBC PAX

PP-03 145 94 210

PP-04 127 119 272

PP-05 36 75 340

PP-06 55 68 281

PP-07 41 78 340

PP-08 86 82 348

PP-09 79 79 354

PP-10 76 55 339

PP-11 78 83 383

PP-12 606 59 0

PP-13 794 101 361

PP-14 465 87 323

PP-15 714 88 355

PP-16 318 88 327

PP-17 254 113 359

0

100

200

300

400

500

600

700

800

900

Reag

en

t D

osa

ge (

g/t

)

Kerosene

Fuel Oil

MIBC

PAX



21

5.7. Metallurgical Results

Although a total of 14 kinetics and circuit surveys were completed, the circuit never reached stability in

the first 9 surveys and, therefore, the resulting mass balances were not used in the analysis of the circuit

performance. Instead those circuit surveys were used to assess only specific parts of the circuit to aid

with the optimization of the operation. The five last surveys were carried with the objective of generating

mass balances to quantify the metallurgical performance of the circuit since stability observations such as

column froth depth, grinding energy power consumption, and froth removal rates were suggesting a

stable condition of the circuit.

In order to generate a full circuit mass balance, the data reconciliation software BILMATTM

was used.

While the software will ensure that the output is balanced in terms of mass and chemical elements, the

user has to incorporate the knowledge of the actual circuit. Aspects to be considered are the level of

confidence in the assays of the various internal and external streams as well as the solids flow rates. This

knowledge is incorporated into the model through adjustments to the measured standard deviation of the

mass and chemical analysis of each product stream. Consequently, there is no single mass balance for a

given survey set, but instead the output is controlled to a certain degree by the user through adjustments

of the measured standard deviation using past experience and the knowledge of the current circuit.

The head assays of the five surveys that are being used to assess the circuit performance are shown in

Table 18. The average BILMATTM

adjusted head grade for the Bisset Creek composite was 2.43 % C(g)

and 1.14 % S. The relative standard deviation of the direct head assays for C(g) and S were 6.9% and

4.3%, respectively. The adjusted values using mass balances that were generated using BilmatTM

slightly

lowered the relative standard deviation of C(g) to 6.6% and increased the relative standard deviation of S

to 9.5%.

Table 18: Head Assays from Pilot Plant Surveys

Direct Adjusted Direct Adjusted

PP-16A 2.43 2.43 0.96 1.08

PP-16B 2.35 2.38 1.06 1.20

PP-16C 2.72 2.35 1.04 1.01

PP17A 2.70 2.38 1.00 1.12

PP17B 2.71 2.74 0.97 1.29

Average 2.58 2.46 1.01 1.14

StdDev 0.18 0.16 0.04 0.11

Rel Std Dev 6.9 6.6 4.3 9.5

S(%)% C(g)Product

Grade



22

A summary of the mass balances of the five surveys is presented in Table 19. The five mass balances

are shown in sequence of the plant operation starting with PP-16A and ending with PP-17B. The

completed mass balances of these surveys with all intermediate streams are included in Appendix B prior

to the operations logs. In order to generate the mass balances, the various product streams were

subjected to two different assay methods depending on the expected carbon grade of the sample. All

products were assayed for total carbon, but the streams with low carbon content were also analyzed with

the graphitic carbon method. This approach was chosen as the graphitic carbon method does not provide

reliable results as the highly hydrophobic properties of the graphite results in mass losses during the

sample preparation stage that is required in the graphitic carbon assay method. For mass balance

purposed, the graphitic carbon assays were for grades of less than 10 % C and the total carbon assays

were used for all other streams. For the products with higher grades, total and graphitic carbon are used

interchangeably.



23

Table 19: Summary of Circuit Mass Balances

The final concentrates of each circuit survey were submitted for a screen analysis followed by C(t)

analysis of the various size fractions. The results for the five concentrates are presented in Table 20. The

product size of the final graphite concentrate from the five surveys was very consistent at P80 = 374-380

microns. Between 45.5% and 49.9% of the concentrate mass reported to the coarsest size fraction of 48

mesh (300 microns), which is very high compared to other graphite deposits.

C(g) S(%) C S



4" Column O/F 1.0 97.0 0.02 39.0 0.0


Mags 0.7 0.14 33.0 0.0 22.1

Non-Mags 95.1 0.16 0.34 6.4 29.9

Feed 100.0 2.43 1.08 100.0 100.0



4" Column O/F 0.2 85.1 0.01 6.6 0.0


Mags 0.2 0.12 30.2 0.0 4.8

Non-Mags 95.6 0.11 0.57 4.2 53.5

Feed 100.0 2.38 1.01 100.0 100.0



4" Column O/F 1.0 96.8 0.01 42.1 0.0


Mags 0.1 0.10 30.2 0.0 4.2

Non-Mags 95.7 0.08 0.57 3.4 54.1

Feed 100.0 2.35 1.01 100.0 100.0



4" Column O/F 0.9 97.1 0.02 35.0 0.0


Mags 1.0 0.16 31.4 0.1 27.2

Non-Mags 94.8 0.18 0.32 7.2 27.1

Feed 100.0 2.38 1.12 100.0 100.0



4" Column O/F 0.3 96.7 0.01 10.2 0.0


Mags 1.2 0.11 30.5 0.0 27.3

Non-Mags 94.6 0.24 0.42 8.4 30.7

Feed 100.0 2.74 1.29 100.0 100.0

Grade % Distribution

PP-17A

PP-17B

Wt %Survey

PP-16A

PP-16B

PP-16C

Product



24

Table 20: Size-by-Size Analysis of Final Graphite Concentrate (PP-16 and PP17)

The S grades in the tailings were still high between 0.34% S and 0.57% S and, therefore, these tailings

would be acid generating without further treatment. Two factors have been identified that resulted in these

elevated S grade concentrations, which were approximately three times higher compared to the lab

results of 0.10-0.15% S. Firstly, the sulphides were floating sluggishly compared to the Master composite

response, which was probably the result of a partial weathering of the sample. A visual comparison of the

bulk composite, the Master composite that was used in 12394-001, and the variability composites that

were tested after the pilot plant campaign revealed a grey colour for the latter two compared to a brown

colour of the pilot plant composite. Secondly, the magnetic separation stage operated less efficient in the

pilot plant as this unit was operating at approximately 750 Gauss compared to at least 1,200 Gauss of the

laboratory scale magnet.

The grab sample profiles for the three concentrate products and the two tailings streams for the extended

run from PP-15 to PP-17 are presented in Figure 14 and Figure 15, respectively. The charts also mark

the time periods when the five surveys in PP-16 and PP-17 were carried out. As evidenced by the charts,

the operation of the graphite cleaner circuit was very stable during the time period when the five surveys

were conducted. During PP-15 and early PP-16 the concentrate grades were still varying more noticeably

and the grade of the concentrate from the small Derrick screen O/S was still increasing. Since the circuit

was started up again at the beginning of PP-15, it is postulated that the circulating streams were still

stabilizing during the first 16-18 hours of operation.

The average grades of the five grab samples for each of the three PP runs as well as the average

for the extended run are presented in

Table 21.

Mesh µm

48 300 49.1 97.7 49.8 49.9 95.1 49.8 49.2 92.7 48.7 48.2 94.4 48.0 45.4 95.4 45.7

65 212 19.6 93.6 19.0 19.3 93.5 19.0 20.8 91.8 20.4 20.6 94.3 20.5 20.2 94.2 20.1

80 180 8.0 97.9 8.1 7.6 96.2 7.7 8.0 97.3 8.3 8.4 96.0 8.5 8.7 97.9 9.0

100 150 5.0 97.8 5.1 4.6 97.8 4.8 4.4 97.5 4.6 4.9 96.7 5.0 5.2 96.8 5.3

150 106 7.8 97.6 7.9 7.3 98.5 7.5 6.2 99.3 6.6 7.3 98.0 7.5 8.5 96.6 8.7

Pan -106 10.5 93.1 10.1 11.3 94.5 11.2 11.4 93.9 11.4 10.7 92.3 10.4 12.0 89.6 11.3

96.4 100.0 95.2 100.0 93.6 100.0 94.8 100.0 100.0 94.9 100.0

SizeGrade

% C(t)

Grade

% C(t)

Grade

% C(t)

Distr.

(%) C(t)

Distr.

(%) C(t)

Distr.

(%) C(t)

PP-16A PP-16B PP-16C PP-17A PP-17B

Total

P80 in µm

Grade

% C(t)

Grade

% C(t)

Ret.

%

Ret.

%

Ret.

%

Ret.

%

Ret.

%

374378379380379

Distr.

(%) C(t)

Distr.

(%) C(t)



25

Figure 14: Grab Sample Profile – Graphite Concentrates (PP-15 to PP-17)

Figure 15: Grab Sample Profile – Graphite Rougher and Scavenger Tailings (PP-15 to PP-17)

60

65

70

75

80

85

90

95

100

6:00 12:00 18:00 0:00 6:00 12:00 18:00

Co

nc

en

tra

te G

rad

e (

% C

(t))

Comb Conc

Small Derrick Screen O/S

4" Column O/F

PP-15 PP-16 PP-17

PP-16A PP-16B

PP-17A

PP-17B

PP-17C

0.0

0.5

1.0

1.5

2.0

2.5

3.0

6:00 12:00 18:00 0:00 6:00 12:00 18:00

Ta

ilin

gs

Gra

de

(%

C(t

))

Scav Tails

Graphite Ro Tail

PP-15 PP-16 PP-17

PP-16A PP-16B PP-17A

PP-17BPP-17C



26

Table 21: Average Total Carbon Assays (%) of Grab Samples (PP-15 to PP-17)

5.8. Pilot Plant Kinetics

One flash and graphite rougher circuit kinetics survey was carried out during PP-12 to determine the

flotation kinetics and evaluate the suitability of the chosen flotation time. In order to generate kinetics

curves, samples of the concentrate of each flotation cell and tailings at the end of each bank were

collected. The concentrates and tailings were submitted for C(t) and C(g) analysis, respectively. The C(t)

grade profile for the flash and graphite rougher stages are presented in Figure 16. As expected, the

highest concentrate grades were achieved in the flash flotation stage and gradually decreased in the 12

flotation cells. The fact that the last incremental concentrate grade of 3.10 % C(t) was still higher than the

head grade of 2.50 C(t) suggests that the chosen flotation time was not excessive.

The tailings grades of the flash flotation bank and the two graphite rougher banks are presented in Figure

17. Based on a direct head grade of 2.50 % C(t), the graphite recovery in the flash flotation stage was

already more than 75%. At the end of the graphite rougher bank #1, the recovery increased to 95.2%,

and the second graphite rougher bank only recovered an addition 0.8% of the graphite for a combined

recovery of 96%.

Based on these kinetics tests, the chosen flotation time for the combined flash and graphite rougher was

a good comprise between the amount of equipment employed and the graphite recovery. In order to

determine if the graphite rougher recovery could be increased further, a third bank of graphite rougher

was incorporated in PP-13. However, on a commercial scale this small incremental graphite recovery

would likely not cover the increased costs to install and operate the additional flotation cells.

Product PP-15 PP-16 PP-17 PP-15 to PP-17

Comb Conc 89.7 91.9 91.8 91.0

Small Derrick Screen O/S 86.3 91.5 93.1 89.7

4" Column O/F 94.1 89.0 97.1 92.6

Scav Tails 2.19 1.33 2.41 1.88

Graphite Ro Tail 0.20 0.23 0.23 0.22



27

Figure 16: Flash and Graphite Rougher Concentrate Kinetics

Figure 17: Flash and Graphite Rougher Tailings Grades

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

Fla

sh C

onc 1

Fla

sh C

onc 2

Fla

sh C

onc 3

Fla

sh C

onc 4

Ro C

on

c 1

Ro C

on

c 2

Ro C

on

c 3

Ro C

on

c 4

Ro C

on

c 5

Ro C

on

c 6

Ro C

on

c 7

Ro C

on

c 8

Gra

ph

ite C

on

cen

trate

Gra

de (

% C

(t))

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

PP-12 Flash Tails PP-12 Graphite Ro Tails 1 PP-12 Graphite Ro Tails 2

Tail

ing

s G

rad

e (

% C

(g))



28

5.9. Environmental Characterization of Pilot Plant Products

Selected pilot plant products were collected during PP-17 and submitted for a basic environmental

characterization. The results for the modified acid-base accounting (ABA) tests and net acid generating

(NAG) tests on those samples are presented in Table 22 and Table 23, respectively. The ABA tests

yielded NP/AP ratios of less than 3.0, which suggests that they are all potentially acid generating based

on the interpretation of solely the ABA test data. The NAG results reveal that all samples possessed a net

acid generating potential for a pH of 7.0 and only the non-magnetic fraction of the sulphide rougher

tailings did not have a net acid generating potential at a pH of 4.5. In conclusion, all pilot plant samples

yielded acid generating potential. However, these tailings are not considered representative of what is to

be expected in the commercial plant since the sulphide minerals were apparently oxidized and a stronger

magnet would be employed to recover additional magnetic sulphide minerals.

Table 22: Modified Acid-Base Accounting Test Results

Sample ID

Sample Date/Time

Analysis Units

Paste pH units 8.39 8.45 8.38 6.47 8.55 8.56

Fizz Rate --- 1 1 2 1 1 1

Sample weight g 1.97 2.01 1.97 1.96 1.99 2.02

HCl added mL 20.0 20.0 20.0 42.5 20.0 20.0

HCl Normality 0.10 0.10 0.10 0.10 0.10 0.10

NaOH Normality 0.10 0.10 0.10 0.10 0.10 0.10

NaOH to pH=8.3 mL 13.4 13.7 13.3 36.9 14.6 13.7

Final pH units 1.44 1.45 1.41 1.62 1.32 1.38

NP t CaCO3/1000 t 16.7 15.7 16.9 14.3 13.6 15.7

AP t CaCO3/1000 t 26.9 16.6 11.1 938 6.87 8.88

Net NP t CaCO3/1000 t -10.2 -0.88 5.83 -924 6.73 6.82

NP/AP ratio 0.62 0.95 1.53 0.02 1.98 1.77

S % 1.16 0.77 0.68 32.2 0.36 0.47

Acid Leachable SO4-S % 0.30 0.24 0.33 2.17 0.13 0.19

Sulphide % 0.86 0.53 0.35 30.0 0.22 0.28

C % 0.199 0.237 0.178 0.215 0.203 0.240

CO3 % 0.400 0.619 0.384 0.605 0.408 0.581

CO3 NP2 t CaCO3/1000 t 6.6 10.3 6.4 10.0 6.8 9.6

CO3 Net NP t CaCO3/1000 t -20.3 -6.3 -4.7 -928.0 -0.1 0.8

CO3 NP/AP Ratio -0.8 -0.4 -0.4 -1.0 0.0 0.1

Classification based on ABA NP1 PAG PAG PAG PAG PAG PAG

Classification based on CO3 NP2 PAG PAG PAG PAG PAG PAG

1 measured in ABA test

2 theoretical, based on CO3 content alone.

Green highlighting indicates Net NP values less than 20.

Orange highlighting indicates NP/AP ratios less than 3.

PAG - Potentially Acid Generating based on interpretation of ABA test data alone.

PAN - Potentially Acid Neutralizing based on interpretation of ABA test data alone.

uncertain - acid generation potential is uncertain based on interpretation of ABA test data alone.

Non-Mags

Sulphide

Ro Only

Non-Mags

Sulphide

Ro & Clnr

Graphite

Rougher

Tails Bank

2

Sulphide

Rougher &

Clnr Tails

Sulphide

Rougher

Tails Mags



29

Table 23: Net Acid Generating Test Results

6. Variability Composites

Eight variability composites were submitted by Northern Graphite, which represented two low-grade, two

medium-grade, and four high-grade zones of the Bisset Creek deposit. The samples were stage-crushed

to -10mesh, homogenized, and split into 2 kg test charges for laboratory testing.

6.1. Head Assays

Representative sub-samples of the eight variability composites were submitted for chemical

characterization including a full carbon speciation, S, and ICP-OES analysis. The results of this analysis

are presented in Table 24. The graphitic carbon head grades ranged from 1.10 % C(g) for low-grade

composite #4 (LG-4) to 3.18% C(g) for high-grade composite #1 (HG-1). The S grades were not

proportional to the graphitic carbon head grade and varied between 1.07% S and 1.54% S.

Sample ID

Sample Date/Time

Analysis Units

Sample weight g 1.50 1.53 1.50 1.52 1.50 1.50

Vol H2O2 mL 150 150 150 150 150 150

Final pH units 2.76 3.15 3.29 2.26 5.97 4.36

NaOH Normality 0.10 0.10 0.10 0.10 0.10 0.10

Vol NaOH to PH 4.5 mL 4.53 1.44 1.08 16.1 0.00 0.07

Vol NaOH to PH 7.0 mL 5.41 2.48 1.98 41.3 0.11 0.45

NAG (pH 4.5) kg H2SO4/tonne 15.0 4.60 3.50 52.0 0.00 0.20

NAG (pH 7.0) kg H2SO4/tonne 18.0 7.90 6.50 133 0.40 1.50

Non-

Mags

Sulphide

Ro & Clnr

Sulphide

Rougher &

Clnr Tails

Sulphide

Rougher

Tails

Graphite

Rougher

Tails Bank

2 Mags

Non-Mags

Sulphide

Ro Only



30

Table 24: Head Analysis Results of Variability Composites

6.2. Batch Flotation

A series of batch flotation tests was completed to validate the flotation conditions prior to locked cycle

testing. A summary of the flotation results is provided in Table 25 and complete mass balances are

included in Appendix C.

LG PIT#3 LG PIT#4 MG PIT#2 MG PIT#4 HG PIT#1 HG PIT#2 HG PIT#3 HG PIT#4

C(t) % 1.45 1.41 1.74 1.59 3.62 3.34 2.55 2.73

C(g) % 1.22 1.10 1.47 1.30 3.18 2.85 2.32 2.61

TOC leco % < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05

CO3 % 1.00 0.95 1.45 1.25 1.75 0.40 < 0.05 < 0.05

S % 1.07 1.22 1.41 1.15 1.54 1.13 1.13 1.05

Ag g/t < 3 < 3 < 3 < 3 < 3 < 3 < 3 < 3

Al g/t 56,000 56,300 53,800 56,700 56,800 58,600 63,300 60,000

As g/t < 30 < 30 < 30 < 30 < 30 < 30 < 30 < 30

Ba g/t 561 592 521 531 549 510 624 512

Be g/t 1.42 1.48 2.14 1.58 1.42 1.6 1.43 1.55

Bi g/t < 20 < 20 < 20 < 20 < 20 < 20 < 20 < 20

Ca g/t 36,000 37,100 38,300 36,700 22,800 18,500 24,900 23,600

Cd g/t < 3 < 3 < 3 < 3 < 3 < 3 < 3 < 3

Co g/t < 20 < 20 < 20 < 20 < 20 < 20 < 20 < 20

Cr g/t 121 123 124 125 95.8 100 110 104

Cu g/t 34.9 43 34.9 35.3 48.1 36.6 38.8 60

Fe g/t 27,500 30,700 30,600 29,000 29,400 28,600 32,100 29,300

K g/t 23,900 25,000 23,300 21,100 25,600 23,400 24,500 22,000

Li g/t < 40 < 40 < 40 < 40 < 40 < 40 < 40 < 40

Mg g/t 22,300 20,800 21,700 19,500 14,600 11,700 14,100 12,400

Mn g/t 689 5,420 2,330 1,050 711 667 728 1,050

Mo g/t < 20 < 20 < 20 < 20 < 20 < 20 < 20 < 20

Na g/t 14,800 14,900 12,900 16,900 9,370 10,400 14,000 13,900

Ni g/t 34 32 41 35 46 34 40 40

P g/t 774 786 854 773 1570 1340 1020 1420

Pb g/t < 40 < 40 < 40 < 40 < 40 < 40 < 40 < 40

Sb g/t < 10 < 10 < 10 < 10 < 10 < 10 < 10 < 10

Se g/t < 30 < 30 < 30 < 30 < 30 < 30 < 30 < 30

Sn g/t < 20 < 20 < 20 < 20 < 20 < 20 < 20 < 20

Sr g/t 152 159 153 165 124 121 156 163

Ti g/t 2,450 2,730 2,310 2,380 2,670 2,610 2,590 2,720

Tl g/t < 30 < 30 < 30 < 30 < 30 < 30 < 30 < 30

U g/t < 20 < 20 < 20 < 20 < 20 < 20 < 20 < 20

V g/t 95 101 111 100 129 118 110 116

Y g/t 21 24 20 20 36 34 23 33

Zn g/t < 2 89 84 76 < 2 < 2 < 2 < 2

CompositeUnitElement



31

Table 25: Summary of Batch Cleaner Tests on Variability Composites

The low-grade and medium-grade composites responded well to the baseline reagent and grinding

conditions and the grade target of 95% C was achieved in the first test on each composite. In contrast,

the higher-grade composites did not upgrade as well in the graphite cleaner circuit and, therefore

produced concentrates with lower graphite grades. Up to three repeat tests were completed with

increasing polishing times, which ultimately improved the concentrate grades to acceptable levels.

6.3. Locked Cycle Flotation

Three different flowsheet variants were evaluated in each LCT to compare the acid-generating potential

of the primary tailings stream. The graphite flash, rougher, and cleaner flotation conditions were

maintained throughout the entire LCT.

Flowsheet option I is depicted in Figure 18 and included a sulphide rougher, followed by a regrind of the

sulphide rougher concentrate and one stage of cleaning. The sulphide rougher and cleaner tailings were

combined to form the low-sulphur tailings stream. The graphite flash, rougher, and cleaner circuits used

the same conditions as the locked cycle test that was completed at the end of the flowsheet development

program 12394-001. Due to the low mass recovery into the flash and rougher concentrates, the cleaning

circuit employed conventional Denver cells instead of flotation columns.

Grade Rec +32 +48 +80 +100 +200 -200 >80

LG Pit #3 96.8 85.0 19.8 37.5 25.9 4.8 9.3 2.7 83.2

LG Pit #4 99.3 82.6 16.6 35.2 23.5 5.1 10.0 2.7 75.3

MG Pit #2 95.6 92.1 24.2 36.8 22.7 4.1 8.1 4.1 83.7

MG Pit #4 98.3 92.6 25.2 33.2 20.3 3.8 9.3 8.2 78.7

HG Pit #1 93.8 96.5 11.7 32.8 28.4 6.7 12.8 7.6 72.9

HG Pit #2 98.5 92.8 16.5 29.8 23.0 4.6 11.1 15.0 69.3

HG Pit #4 96.9 94.6 18.1 33.7 25.5 4.9 10.9 7.0 77.2

Final Concentrate C(t)Composite




32

Figure 18: Flowsheet Option I – Cycles A& B

The flowsheet option II is presented in Figure 19 and is based on option I with the addition of a magnetic

separation of the combined low-sulpur tailings to recover any additional sulphide units that are magnetic.

The last flowsheet option III, which is depicted in Figure 20 only, includes a magnetic separation stage,

but no sulphide rougher or cleaning circuit. Samples of the various tailings were submitted for net acid

generating potential tests (NAG) and modified acid-base accounting tests (ABA) to determine the acid-

generating potential of the low-sulphur tailings stream that is generated by each flowsheet option. The

results are discussed in a separate section.



33

Figure 19: Flowsheet Option II – Cycles C & D

Figure 20: Flowsheet Option III – Cycles E & F



34

A summary of the mass balance results of the eight locked cycle tests is presented in Table 26 and the

complete test data are included in Appendix D. All eight variability composites responded well to the

flowsheet and produced graphitic carbon recoveries between 95.2% and 99.1%. The corresponding

concentrate grades ranged between 93.5% C and 96.5% C. The chemical analysis that was carried out to

determine the concentrate grade used LECO without the roast that is typically completed for a graphitic

carbon analysis. Although the preparation procedure for the roasting step has been substantially

improved to address the physical challenges that the highly hydrophobic graphite flakes generate, the

analysis still proved inaccurate for high grade concentrates and always underestimated the grades by as

much as 20% C. Hence, total carbon results are used interchangeably for graphitic carbon for the final

concentrates with the assumption that all carbonaceous and organic carbon was rejected in the rougher

and cleaning stages.



35

Table 26: Summary of Locked Cycle Mass Balances

% C(t,g) S C(t,g) SFinal Concentrate 1.4 93.5 - 96.8Sec 1st Clnr Tails 0.0 14.8 - 0.3

Pri 1st Clnr Tails 2.5 0.15 - 0.3

Sulphide Conc 2.1 0.25 32.7 0.4 59.7

Sulphide 1st Clnr Tails 2.1 0.03 14.95 0.1 26.6

Sulphide Ro Tails 91.9 0.03 0.17 2.2 13.8

Head (calc) 100.0 1.38 1.16 100.0 100.0

Head (direct) 1.22 1.07

Final Concentrate 1.4 93.7 - 95.2Sec 1st Clnr Tails 0.1 8.3 - 0.3Pri 1st Clnr Tails 2.8 0.18 - 0.4

Sulphide Conc 2.5 0.15 31.2 0.3 66.4



Head (calc) 100.0 1.35 1.18 100.0 100.0


Final Concentrate 1.6 96.5 - 97.7Sec 1st Clnr Tails 0.0 28.9 - 0.4


Sulphide Conc 2.3 0.20 36.3 0.3 60.0



Head (calc) 100.0 1.60 1.37 100.0 100.0




Sulphide Conc 2.1 0.26 29.1 0.3 57.0



Head (calc) 100.0 1.58 1.09 100.0 100.0




Sulphide Conc 3.0 0.19 33.4 0.2 83.1



Head (calc) 100.0 3.22 1.20 100.0 100.0




Sulphide Conc 2.9 0.34 39.4 0.3 79.6



Head (calc) 100.0 3.66 1.44 100.0 100.0




Sulphide Conc 2.9 0.19 27.9 0.2 71.8



Head (calc) 100.0 2.56 1.14 100.0 100.0




Sulphide Conc 3.4 0.15 25.4 0.1 74.1



Head (calc) 100.0 3.52 1.16 100.0 100.0


LCT HG-4

ProductWeight Assay (%) Distribution (%)

Test

LCT LG-4

LCT LG-3

LCT MG-2

LCT MG-4

LCT HG-1

LCT HG-2

LCT HG-3



36

The flake size distribution of the final graphite concentrates of the six locked cycle tests is presented in

Table 27. While the amount of flakes greater than 32 mesh varied substantially between 11.2% and

25.7% by mass, the -32mesh/+48 mesh size fraction was very consistent at 31.9% to 35.1% by mass. As

a result, the mass of the +48 mesh fraction ranged between 43.1% and 58.5% by mass. These results

are in agreement with the data obtained during the flowsheet development program and the pilot plant

campaign.

Table 27: Flake Size Distribution of Final Graphite Concentrates from LCTs

6.4. Environmental Characterization of LCT Products

Samples of selected flotation products from three LCTs (LCT LG-3, LCT MG-2, and LCT HG-4) were

subjected to a basic environmental characterization consisting of a NAG and ABA test on each product.

The ABA and NAG results are summarized in Table 28 and Table 29, respectively, and the test

certificates are included in Appendix E.

Based on the ABA and NAG results, the flowsheet option I (sulphide rougher only – the sulphide rougher

concentrate constitutes a final high-sulphur tailings product) and option II (sulphide circuit and magnetic

separation on the combined sulphide rougher tailings and sulphide 1st cleaner concentrate) produced

tailings that were classified as non-acid generating. Flowsheet option II will minimize the amount of high-

sulphur tailings to be disposed.

+32 +48 +80 +100 +200 -200 >80

LG Pit #3 19.0 32.8 23.2 5.0 10.4 9.5 75.1

LG Pit #4 22.6 32.6 20.1 4.6 9.5 10.5 75.3

MG Pit #2 23.7 34.1 22.1 3.9 8.7 7.5 79.9

MG Pit #4 25.7 32.8 19.9 3.8 9.3 8.4 78.4

HG Pit #1 11.2 31.9 28.1 7.0 12.8 9.0 71.2

HG Pit #2 14.8 32.8 25.9 5.9 12.0 8.6 73.5

HG Pit #3 20.2 35.1 22.7 5.3 9.3 7.4 78.0

HG Pit #4 15.7 32.0 24.4 6.0 11.7 10.2 72.1

Minimum 11.2 31.9 19.9 3.8 8.7 7.4 71.2

Maximum 25.7 35.1 28.1 7.0 12.8 10.5 79.9

Average 19.1 33.0 23.3 5.2 10.5 8.9 75.4

StdDev 4.9 1.1 2.8 1.1 1.5 1.2 3.1

Rel StdDev 25.8 3.3 12.0 21.4 14.3 13.0 4.1

Composite




37

Table 28: Acid-Base Accounting Test Results for LCT Products

Modified Acid Base Accounting

Parameter Unit

Sulphide

Conc

A,B,C,D

Magsep

Conc

C,D,E,F

Magsep

Tails C,D

Magsep

Tails E,F

Combined

Sample

Sulphide

Conc

A/B/C/D

Sulphide 1st

Clnr Tails

A/B/Rougher

Tails A/B

Magsep

Conc

C/D/E/F

Magsep

Tails C/D

Magsep

Tails E/F

Comb

Sulphide

Conc

A/B/C/D

Comb

Sulphide Tails

clnr/rougher

A/B

Comb

Magsep

Conc

C/D/E/F

Comb

Magsep

Tails C/D

Comb

Magsep

Tails E/F

LIMS 11130-JAN1211130-JAN1211130-JAN1211130-JAN1211130-JAN1211283-JAN1211283-JAN12 11283-JAN1211283-JAN1211283-JAN1211134-FEB1211134-FEB12 11134-FEB1211134-FEB1211134-FEB12

Paste pH units 5.4 8.22 9.65 9.66 9.68 7.01 9.88 8.4 10.03 9.98 6.7 8.16 7.85 8.29 8.54

Fizz Rate --- 1 2 2 2 2 1 1 1 1 1 3 3 1 3 3

Sample weight g 1.97 1.99 2.02 2.03 2.01 2 2.02 2.01 1.99 1.97 2.05 2.01 2.02 2.02 1.96

HCl added mL 24.50 24.10 20.00 20.00 20.00 36.70 20.00 33.60 20.00 20.00 20.00 20.00 25.60 20.00 20.00

HCl Normality 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10

NaOH Normality 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10

NaOH to pH=8.3 mL 22.15 19.90 14.51 14.52 14.44 31.08 13.86 26.58 14.52 14.49 11.16 8.00 18.65 7.59 14.69

Final pH units 1.64 1.64 1.29 1.32 1.34 1.63 1.51 1.63 1.34 1.34 1.58 1.67 1.79 1.74 1.2

NP1t CaCO3/1000 t 6 10.6 13.6 13.5 13.8 14 15.2 17.50 13.8 14 21.6 29.8 17.2 30.7 13.6

AP t CaCO3/1000 t 1040 319 0.71 3.71 6.74 789 8.8 250 0.62 2.16 838 6.1 103 4.34 11.5

Net NP t CaCO3/1000 t -1034 -308 12.9 9.8 7.1 -775.0 6.4 -232 13.2 11.8 -816 23.7 -85.8 26.4 2.1

NP/AP ratio 0.01 0.03 19.1 3.6 2 0.02 1.73 0.07 22.4 6.47 0.03 4.89 0.17 7.08 1.18

S % 33.1 13.8 0.095 0.181 0.61 25.8 0.52 12.6 0.057 0.12 28.5 0.353 14.1 0.181 0.357

SO4 % < 0.01 3.6 0.07 0.06 0.39 0.55 0.23 4.6 0.04 0.05 1.65 0.16 10.8 0.04 < 0.01

Sulphide % 33.3 10.2 0.02 0.12 0.22 25.2 0.28 7.99 0.02 0.07 26.8 0.2 3.3 0.14 0.37

C % 0.309 0.082 0.109 0.117 0.125 0.342 0.102 0.126 0.105 0.109 0.595 0.347 0.109 0.317 0.09

Carbonate % 0.937 0.118 0.275 0.364 0.262 0.926 <0.184 <0.205 0.32 <0.307 2.06 <1.350 <0.503 <1.510 <0.471

CO3 NP2 t CaCO3/1000 t 15.6 2.0 4.6 6.0 4.3 15.4 3.1 3.4 5.3 5.1 34.2 22.4 8.3 25.1 7.8

CO3 Net t CaCO3/1000 t -1024.4 -317.0 3.9 2.3 -2.4 -773.6 -5.7 -246.6 4.7 2.9 -803.8 16.3 -94.7 20.7 -3.7

CO3 NP/AP ratio 0.015 0.006 6.430 1.629 0.645 0.019 0.347 0.014 8.568 2.359 0.041 3.674 0.081 5.776 0.680

Classification based on ABA NP1 PAG PAG uncertain uncertain uncertain PAG uncertain PAG uncertain uncertain PAG PAN PAG PAN uncertain

Classification based on CO3 NP2PAG PAG uncertain uncertain PAG PAG PAG PAG uncertain uncertain PAG uncertain PAG PAN PAG

1 measured in ABA test PAG PAG PAN uncertain PAG PAG PAG PAG PAN uncertain PAG PAN PAG PAN PAG2 theoretical, based on CO

3 content alone.

Green highlighting indicates Net NP values less than 20.

Orange highlighting indicates NP/AP ratios less than 3.

PAG - Potentially Acid Generating based on interpretation of ABA test data alone.

PAN - Potentially Acid Neutralizing based on interpretation of ABA test data alone.

uncertain - acid generation potential is uncertain based on interpretation of ABA test data alone.

LCT MG2 LCT HG4LCT LG3



38

Table 29: Net Acid Generating Tests for LCT Products

NAG Test - LCT LG-3

Parameter Unit Sulphide Conc A/B/C/D Comb Sulp. 1st Clnr & Ro Tails A/B Magsep Conc C/D/E/F Magsep Tails C/D Magsep Tails E/F

Sample weight(g) 1.47 1.49 1.49 1.47 1.49

Vol H2O2 ml 150 150 150 150 150

Final ph units 2.66 3.82 1.95 8.14 7.97

NaOH Normality 0.10 0.10 0.50 0.10 0.10

Vol NaOH to pH 4.5 ml 8.7 0.3 7.0 0.0 0.0

Vol NaOH to pH 7.0 ml 28.1 1.0 9.5 0.0 0.0

NAG @pH4.5 29.0 0.9 115.0 0.0 0.0

NAG @pH7 93.6 3.1 156.0 0.0 0.0

NAG Test - LCT MG-2

Parameter Unit Sulphide Conc A/B/C/D Sulhide 1st Clnr Tails Ro Tails Magsep Tails C/D Magsep Tails E/F

Sample weight(g) 1.49 1.5 1.47 1.54 1.46

Vol H2O2 ml 150 150 150 150 150

Final ph units 2.95 2.03 8.02 7.35 3.51

NaOH Normality 0.10 0.50 0.10 0.10 0.10

Vol NaOH to pH 4.5 ml 4.8 6.4 0.0 0.0 0.7

Vol NaOH to pH 7.0 ml 20.6 9.2 0.0 0.0 1.6

NAG @pH4.5 16.0 104.0 0.0 0.0 2.4

NAG @pH7 68.0 150.0 0.0 0.0 5.4

NAG Test - LCT HG-4

Parameter Unit Sulphide Conc A/B/C/D Sulhide 1st Clnr Tails Ro Tails Magsep Tails C/D Magsep Tails E/F

Sample weight(g) 1.46 1.49 1.47 1.48 1.49

Vol H2O2 ml 150 150 150 150 150

Final ph units 1.95 2.45 8.84 9.98 3.55

NaOH Normality 0.50 0.10 0.10 0.10 0.10

Vol NaOH to pH 4.5 ml 6.4 9.4 0.0 0.0 0.5

Vol NaOH to pH 7.0 ml 9.5 17.7 0.0 0.0 0.9

NAG @pH4.5 107.0 31.0 0.0 0.0 1.7

NAG @pH7 159.0 58.0 0.0 0.0 2.9



39

7. Product Characterization and Handling

A number of sub-samples were collected during the pilot plant campaign for vendor and environmental

testing, A summary of the samples that were shipped are provided in the following sections. Any test

results were reported directly to Northern Graphite and, therefore, are not included in this document.

• 4 drums of decanted flash flotation tailings were shipped to Derrick in Buffalo on January 3, 2012

for screening tests.

• Approximately 10 kg of final graphite concentrate was shipped to URSTM on December 16, 2011

for static settling tests.

• Six pails of final plant process water were shipped to Aquatox in Guelph for toxicity tests on

December 12, 2011.

• Samples of the tailings products collected at the end of PP-17 were forwarded to Knight Piesold

for environmental characterization tests. The products included the sulphide 1st cleaner

concentrate and the non-magnetic product, which represents the primary plant tailings.

8. Conclusions and Recommendations

The pilot plant campaign on the Bisset Creek pilot plant sample produced a number of mechanical and

metallurgical challenges that required 14 shifts of operation to overcome. The primary mechanical

challenges were created by the coarse flotation feed, which was up to 8 times coarser compared to most

other flotation pilot plants. In order to prevent sanding out of the flotation cells, the feed solids

concentration and the sand port configuration were adjusted until a steady operation was obtained. Also

routing of the pulp transfer lines was changed in a number of instances.

The majority of metallurgical challenges arose from the fact that the bulk sample produced a different

flotation response in the pilot plant compared to the Master composite in the laboratory tests. While the

drill core that was received from the Bisset Creek deposit was typically grey in colour, the bulk sample

was distinctively brown. Discussions with the clients reveal that this sample was extracted from an area

directly underneath a zone that was visually weathered. These observations combined with the fact that

the flotation kinetics and overall recovery of the sulphide minerals were very poor, lead to the conclusion

that even the bulk sample was partially weathered.

A number of changes to the circuit and reagent regime were carried out to improve the flotation response

of the bulk sample. The collector dosages in both the graphite and sulphide circuits were up to 10 times

higher compared to the laboratory tests. In the case of the graphite circuit, the difficulty to control the

addition rate of neat fuel oil contributed to the high dosage rate. An effort was made to reduce the fuel oil

dosages during the extended run in PP-16 and PP-17, but more operating time would have been required

to further optimize the dosage. All locked cycle tests that were carried out on the variability composites



40

used a kerosene dosage of 37.5 g/t, which proved sufficient for the process. Considering the fact that the

locked cycle tests did not recycle the process water, the required collector dosage is expected to be

below that value. Taking into account the collector dosages in the lab and the pilot scale, a fuel oil

consumption of 100 g/t in the full-scale plant is considered a conservative number.

In order to generate low-sulphur tailings streams that are non-acid generating, the proposed flotation

circuit should include a sulphide rougher and cleaner circuit and a magnetic separator to treat the

sulphide tailings.

Due to the focus on the graphite flotation circuit, the reagent dosages in the sulphide circuit were not

optimized. In addition, the sample oxidation led to much slower flotation kinetics of the sulphide minerals

and a significant percentage of the sulphides could not be recovered by means of flotation. In order to

develop a better understanding of the PAX dosage that would be required to achieve a satisfactory

sulphide recovery, a series of rougher kinetics tests were completed after the pilot plant campaign. In

those tests, the total PAX dosage in the sulphide rougher and cleaner stages were gradually increased

from 75 g/t to 225 g/t. The results of the tests are summarized in Table 30. The test data reveal that the

sulphur grade of the magnetic separation tailings did not increase as the PAX dosage was gradually

reduced. Even at a PAX dosage of 75 g/t, less than 4% of the sulphides reported to the low-sulphur

tailings stream. Hence, it is recommended to use a PAX dosage of 100 g/t for design purposes.

Table 30: Summary of PAX Dosage Tests

Although a graphite concentrate grading 95% C was obtained towards the end of the pilot plant

campaign, the overall recovery fell short compared to the results obtained in the laboratory tests. It is

postulated that this was primarily the result of insufficient time to optimize the circuit after all mechanical

Weight Assay (%) Distr. (%)

% S S

Sulphide 1st Clnr Conc 2.83 28.6 56.4

MagSep Feed 97.2 0.64 43.6

Magsep Conc 4.67 12.2 39.7

MagSep Tails 92.5 0.06 3.9

Head ( calc. ) 100.0 1.43 100

Head (direct) 1.41


MagSep Feed 97.2 0.60 39.8

Magsep Conc 4.22 12.4 35.9


Head ( calc. ) 100.0 1.46 100

Head (direct) 1.41


MagSep Feed 96.2 0.41 27.0

Magsep Conc 3.96 8.8 23.9


Head ( calc. ) 100.0 1.46 100

Head (direct) 1.41


MagSep Feed 96.7 0.47 30.2

Magsep Conc 3.67 10.0 24.6


Head ( calc. ) 100.0 1.49 100

Head (direct) 1.41

ProductTest

S-1

75 g/t PAX

S-2

110 g/t

PAX

S-3

150 g/t

PAX

S-4

225 g/t

PAX



41

and metallurgical issues were resolved. The variability composites produced consistently high

concentrate grades and recoveries in the locked cycle tests. Typically, optimized pilot plant conditions

produce comparable or even superior results compared to the laboratory-scale data, which further

supports the statement that the pilot plant had not reached its optimum operating point at the time the ore

was depleted.

The pilot plant campaign demonstrated that a high-grade graphite concentrate could be produced from

the Bisset Creek mineralization and that approximately 50% of the graphite flakes reported to the +48

mesh size fraction.



42

Appendix A – Comminution Test Data



43

Appendix B – Pilot Plant Operation Logs



44

Appendix C – Variability Batch Flotation Test Data



45

Appendix D – Variability Locked Cycle Test Data



46

Appendix E – NAG and ABA Certificates

prepared for northern graphite - ontario · primary rod grind-marcy (p 80 ~ 1,200 microns)...

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