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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Final Graphite Conc 2.4 94.4 0.01 94.5 0.0
Graphite 1st Clnr Conc Screen O/S 2.2 95.2 0.01 87.9 0.0
4" Column O/F 0.2 85.1 0.01 6.6 0.0
Sulphide 1st Clnr Conc 1.8 1.65 23.2 1.3 41.6
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
Final Graphite Conc 2.4 93.2 0.01 94.9 0.0
Graphite 1st Clnr Conc Screen O/S 1.4 90.5 0.01 52.8 0.0
4" Column O/F 1.0 96.8 0.01 42.1 0.0
Sulphide 1st Clnr Conc 1.8 2.15 23.2 1.6 41.6
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
Final Graphite Conc 2.3 93.4 0.01 91.6 0.0
Graphite 1st Clnr Conc Screen O/S 1.5 91.2 0.02 56.6 0.0
4" Column O/F 0.9 97.1 0.02 35.0 0.0
Sulphide 1st Clnr Conc 1.9 1.43 27.5 1.1 45.7
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
Final Graphite Conc 2.6 95.2 0.01 90.5 0.0
Graphite 1st Clnr Conc Screen O/S 2.3 95.0 0.01 80.2 0.0
4" Column O/F 0.3 96.7 0.01 10.2 0.0
Sulphide 1st Clnr Conc 1.6 1.93 34.0 1.1 41.9
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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)
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Final Concentrate 1.4 93.7 95.2
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
Final Concentrate 3.4 93.7 99.1
Head (calc) 100.0 3.22 100.0Head (direct) 3.18
Final Concentrate 3.7 95.5 96.2
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
Final Concentrate 3.6 95.9 98.3
Head (calc) 100.0 3.52 100.0Head (direct) 2.61
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)
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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:
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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.
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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.
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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.
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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
Northern Graphite – Bisset Creek– Project 12394-02 – FINAL DRAFT
SGS Minerals Services
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)
D7-Tank D7-Tank D7-Tank D7-Tank
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 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
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Graphite Rougher Cell #3 Kerosene 1.0 2.5 1.5
MIBC 1.0 5.0 3.0
Graphite Rougher Cell #5 Kerosene 1.0 2.5 1.5
MIBC 1.0 5.0 3.0
Graphite Rougher Cell #7 Kerosene 1.0 2.5 1.5
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
Sulphide Rougher Cell #3 PAX 5.0 16.7 49.5
MIBC 1.0 0.0 0.0
Sulphide Rougher Cell #5 PAX 5.0 16.7 49.5
MIBC 1.0 0.0 0.0
Sulphide Rougher Cell #7 PAX 5.0 8.4 24.7
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
Sulphide Cleaner Cell #3 PAX 5.0 0.0 0.0
MIBC 1.0 0.0 0.0
Sulphide Cleaner Cell #5 PAX 5.0 4.2 12.3
MIBC 1.0 0.0 0.0
Sulphide Cleaner Cell #7 PAX 5.0 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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
)
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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)
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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.
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
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
Final Graphite Conc 2.4 94.4 0.01 94.5 0.0
Graphite 1st Clnr Conc Screen O/S 2.2 95.2 0.01 87.9 0.0
4" Column O/F 0.2 85.1 0.01 6.6 0.0
Sulphide 1st Clnr Conc 1.8 1.65 23.2 1.3 41.6
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
Final Graphite Conc 2.4 93.2 0.01 94.9 0.0
Graphite 1st Clnr Conc Screen O/S 1.4 90.5 0.01 52.8 0.0
4" Column O/F 1.0 96.8 0.01 42.1 0.0
Sulphide 1st Clnr Conc 1.8 2.15 23.2 1.6 41.6
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
Final Graphite Conc 2.3 93.4 0.01 91.6 0.0
Graphite 1st Clnr Conc Screen O/S 1.5 91.2 0.02 56.6 0.0
4" Column O/F 0.9 97.1 0.02 35.0 0.0
Sulphide 1st Clnr Conc 1.9 1.43 27.5 1.1 45.7
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
Final Graphite Conc 2.6 95.2 0.01 90.5 0.0
Graphite 1st Clnr Conc Screen O/S 2.3 95.0 0.01 80.2 0.0
4" Column O/F 0.3 96.7 0.01 10.2 0.0
Sulphide 1st Clnr Conc 1.6 1.93 34.0 1.1 41.9
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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)
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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))
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Flake Size Distribution - % retained (mesh)
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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.
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
33
Figure 19: Flowsheet Option II – Cycles C & D
Figure 20: Flowsheet Option III – Cycles E & F
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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.
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Sulphide 1st Clnr Tails 1.2 0.04 12.45 0.0 12.9
Sulphide Ro Tails 92.0 0.05 0.26 3.7 20.7
Head (calc) 100.0 1.35 1.18 100.0 100.0
Head (direct) 1.45 1.22
Final Concentrate 1.6 96.5 - 97.7Sec 1st Clnr Tails 0.0 28.9 - 0.4
Pri 1st Clnr Tails 2.0 0.34 - 0.4
Sulphide Conc 2.3 0.20 36.3 0.3 60.0
Sulphide 1st Clnr Tails 1.9 0.03 21.15 0.0 28.6
Sulphide Ro Tails 92.3 0.02 0.17 1.2 11.4
Head (calc) 100.0 1.60 1.37 100.0 100.0
Head (direct) 1.47 1.41
Final Concentrate 1.6 95.4 - 96.8Sec 1st Clnr Tails 0.0 16.8 - 0.4
Pri 1st Clnr Tails 2.7 0.19 - 0.3
Sulphide Conc 2.1 0.26 29.1 0.3 57.0
Sulphide 1st Clnr Tails 1.5 0.04 9.32 0.0 13.0
Sulphide Ro Tails 92.0 0.04 0.36 2.0 30.0
Head (calc) 100.0 1.58 1.09 100.0 100.0
Head (direct) 1.30 1.15
Final Concentrate 3.4 93.7 - 99.1Sec 1st Clnr Tails 0.1 5.9 - 0.2
Pri 1st Clnr Tails 6.3 0.05 - 0.1
Sulphide Conc 3.0 0.19 33.4 0.2 83.1
Sulphide 1st Clnr Tails 2.7 0.12 4.00 0.1 8.8
Sulphide Ro Tails 84.6 0.01 0.12 0.3 8.1
Head (calc) 100.0 3.22 1.20 100.0 100.0
Head (direct) 3.18 1.54
Final Concentrate 3.7 95.5 - 96.2Sec 1st Clnr Tails 0.1 21.1 - 0.8
Pri 1st Clnr Tails 5.7 1.14 - 1.8
Sulphide Conc 2.9 0.34 39.4 0.3 79.6
Sulphide 1st Clnr Tails 3.1 0.11 4.41 0.1 9.6
Sulphide Ro Tails 84.5 0.04 0.18 0.8 10.8
Head (calc) 100.0 3.66 1.44 100.0 100.0
Head (direct) 3.34 1.13
Final Concentrate 2.6 95.3 - 97.1Sec 1st Clnr Tails 0.0 16.5 - 0.3
Pri 1st Clnr Tails 4.9 0.09 - 0.2
Sulphide Conc 2.9 0.19 27.9 0.2 71.8
Sulphide 1st Clnr Tails 2.0 0.08 10.26 0.1 17.9
Sulphide Ro Tails 87.6 0.07 0.13 2.2 10.4
Head (calc) 100.0 2.56 1.14 100.0 100.0
Head (direct) 2.32 1.07
Final Concentrate 3.6 95.9 - 98.3Sec 1st Clnr Tails 0.1 19.2 - 0.6
Pri 1st Clnr Tails 6.2 0.16 - 0.3
Sulphide Conc 3.4 0.15 25.4 0.1 74.1
Sulphide 1st Clnr Tails 3.7 0.05 4.22 0.0 13.4
Sulphide Ro Tails 83.0 0.03 0.18 0.6 12.5
Head (calc) 100.0 3.52 1.16 100.0 100.0
Head (direct) 2.61 1.05
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Flake Size Distribution - % retained (mesh)
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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
Sulphide 1st Clnr Conc 2.82 31.1 60.2
MagSep Feed 97.2 0.60 39.8
Magsep Conc 4.22 12.4 35.9
MagSep Tails 93.0 0.06 3.8
Head ( calc. ) 100.0 1.46 100
Head (direct) 1.41
Sulphide 1st Clnr Conc 3.80 28.1 73.0
MagSep Feed 96.2 0.41 27.0
Magsep Conc 3.96 8.8 23.9
MagSep Tails 92.2 0.05 3.2
Head ( calc. ) 100.0 1.46 100
Head (direct) 1.41
Sulphide 1st Clnr Conc 3.32 31.4 69.8
MagSep Feed 96.7 0.47 30.2
Magsep Conc 3.67 10.0 24.6
MagSep Tails 93.0 0.09 5.6
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
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
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.
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
42
Appendix A – Comminution Test Data
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
43
Appendix B – Pilot Plant Operation Logs
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
44
Appendix C – Variability Batch Flotation Test Data
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
45
Appendix D – Variability Locked Cycle Test Data
Northern Graphite – Bisset Creek – 12394-002
SGS Minerals Services
46
Appendix E – NAG and ABA Certificates