Aitik Mill as a Hub for a satellite mine

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Aitik mill as hub for a satellite minePreliminary development plan of a satellite copper deposit

Melissa Markesteijn BTA/RE/14-06

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Aitik mill as hub for a satellite mine

Preliminary development plan of a satellite copper deposit

by Melissa Markesteijn

In partial fulllment of the requirements for the degree of

Bachelor of Sciencein Applied Earth Sciences

at the Delft University of Technology.

First Supervisor: Dr. ir. J. Benndorf Second Supervisor: Dr. ir. D.J.M. Ngan-TillardSupervisor at Boliden: A. Renström

An electronic version of this thesis is available at http://repository.tudelft.nl/ .

http://repository.tudelft.nl/http://repository.tudelft.nl/http://repository.tudelft.nl/


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A BSTRACT

The copper grade in the Aitik mine in northern Sweden is decreasing, therefore other deposits areinvestigated. One of these deposits is the satellite deposit discussed in this thesis. The grade of thisdeposit is higher than in Aitik and could thus be used to increase the copper production at the Aitik mine site.

The goal of this thesis is to establish a preliminarydevelopmentplan for a satellite copper deposit, which will be processed at the Aitik processing plant.

A literature study showed that the geology of the Aitik mine is the same as that of the satellitemine. Therefore the same design properties could be used as in the Aitik mine.

Because of the small surface operation and a steeply dipping ore, the best surface method for thesatellite mine is an open-pit operation. The mine design will slightly differ from the Aitik design, the

overall slope angle will be higher which results in less waste and thus less extracting costs. The overallslope could be made higher by a smaller bench width.

Different cut-off values and elevations of the pit bottom are tried. The best result was obtained with an elevation of the pit bottom of 400 meters. This means that the pit will be 85 meters deep,since the average surface elevation is 485 meters. For the cut-off value is found that the best cut-off value is 55 SEK. This would result in a maximum prot.

The fragmentation of the ore could best be done using a ner blasting schedule, instead of using an in-pit crusher. The costs of ner blasting is less than that of an in-pit crusher.

The production schedule shows that the surface operation of this satellite mine will be from the1st of January 2018 to the 29 th of May 2024, this means that the open-pit mine will produce for justunder 6,5 years. These dates are hypothetical and depend on the real starting date. After that a un-

derground operation is considered. When this production schedule is used the Net Present Value of the project will be 59,9 MSEK.

Therefore this project is economically protable, although the prot is fairly low. However, theprospectsof a high-grade underground mine are promising. Therefore thiswill be a protableproject.

It is recommended for this project to do a more thorough research. The accuracy of grade inthe ore body is not very high, so this should be evaluated by drilling more boreholes. More modelsshould be evaluated, different cut-off values could be used, but also different production times couldbe considered to mine the ore quicker and start earlier with the underground operation.

Also, a leaching plant at the Aitik processing site should be considered. More and more gold andsilver is extracted from the Aitik area, but the recovery of these metals is fairly low, this could be in-creased by a leaching operation.

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CONTENTS

Abstract ii

List of Figures iii

List of Tables iv

Preface v

1 Introduction 11.1 Relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Goal and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Report overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 The Aitik mine and its region 32.1 Geological Setting of the region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 The Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Processing the copper ore 63.1 Crushing the ore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Grinding and milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Flotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.4 Limitations of the processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 The satellite mine 9

4.1 Analysis of the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Fragmentation of the ore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Production schedule and economic evaluation 155.1 Production schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155.2 Economic evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 Conclusions 19

7 Recommendations 20

Bibliography 21

Appendix A: Calculations for the satellite mine 23 A.1 Waste Reduction when using a 2 degrees steeper slope . . . . . . . . . . . . . . . . . . . 23 A.2 Different elevations cut-off of 55 SEK and 124 SEK . . . . . . . . . . . . . . . . . . . . . 24 A.3 Kuz-ram models for blasting to 300 and 1200 millimeters . . . . . . . . . . . . . . . . . 25

Appendix B: Production Schedule 26B.1 Summary of the stage 1 production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26B.2 Summary of the stage 2 production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27B.3 Total production overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Appendix C: Economic Evaluation 30C.1 Calculation of the Net Present Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

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LIST OF FIGURES

1.1 Expected copper grades at the Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1 The location of the Aitik mine and itsregionin the northern part of Sweden ( McGimpsey,2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Geology of Northern Sweden ( Wanhainen et al., 2012 ) . . . . . . . . . . . . . . . . . . . . 42.3 Schematic west-east vertical section through the Gällivare area . . . . . . . . . . . . . . . 5

3.1 The processing process at the Aitik processing site . . . . . . . . . . . . . . . . . . . . . . 63.2 The Mills at Aitik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Principle of otation ( Kawatra , 2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.1 A simple model of the ore at the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Cross section of the block model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.3 The bench design of the satellite mine. Note that this drawing is hypothetical and not

to scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5.1 The outline of the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

A.1 The Kuz-ram model for blasting to 300 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 A.2 The Kuz-ram model for blasting to 1200 mm . . . . . . . . . . . . . . . . . . . . . . . . . . 25

B.3 Production Schedule Summary per bench . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

B.4 The gold and silver grades in the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . 28

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LIST OF T ABLES

2.1 Rock properties in the Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 The amount of ore in the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.2 The waste reduction if a steeper slope is used . . . . . . . . . . . . . . . . . . . . . . . . . 114.3 Cut-off calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.4 Properties of the emulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.5 Costs for the drilling and blasting with an Atlas Copco SmartROC D65 . . . . . . . . . . . 134.6 The variables used for the blasting to 300 mm . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.1 The total amount of days to mine the two stages and its start and end date . . . . . . . . 16

5.2 Summary of the production per year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.3 The production of the trace elements gold and silver . . . . . . . . . . . . . . . . . . . . . 165.4 The long-term prices of copper, gold and silver . . . . . . . . . . . . . . . . . . . . . . . . 175.5 NPV Model for different NSR values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.6 NPV Model for different capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

A.1 Waste Reduction Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 A.2 Optimum pit depth calculated for two cut-off values . . . . . . . . . . . . . . . . . . . . . 24

B.1 Summary of the production per month for stage 1 . . . . . . . . . . . . . . . . . . . . . . 26B.2 Summary of the production per year for stage 2 . . . . . . . . . . . . . . . . . . . . . . . . 27

C.1 The overall NPV Calculation of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

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P REFACE

This report is written as a Bachelor thesis at the end of the Applied Earth Sciences Bachelor’s programof the TU Delft in The Netherlands. The project is done for the company Boliden, with locations inScandinavia and Ireland. This report focuses on the Aitik mine in Sweden, in particular on a satellitemine which will be located 15 kilometers away from the Aitik mine site. This thesis is part of a pre-feasibility study.

I want to thank a few people who did help me to do this project. First of all, I want to thank Dr. ir.J.Benndorf and Dr. ir. D.J.M. Ngan-Tillard for their support and supervision from the TU Delft. Andof course I want to thank Arne Renström from Boliden, without whom I wouldn’t have been able to work on this project. I also want to thank Boliden for providing all the necessary data to work with.

This report would not have been possible without the support of all the employees of Boliden, atthe ofce and at the Aitik mine site.

Melissa Markesteijn

Delft, June 2014

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1INTRODUCTIONIn this rst chapter the main objective of this research is presented. The chapter closes with a shortoutline of each chapter.

1.1. RELEVANCEThe Aitik mine in northern Sweden is one of the biggest open pit copper mines in Europe. The minehas produced copper since 1968. However, over the years the copper grade has drastically decreased.The copper grade will decrease further in the next decade (Figure 1.1).

Figure 1.1: Expected copper grades at the Aitik mine

Around this Aitik mine, there are different other satellite deposits which are rich in copper. Oneof them is located just 15 kilometers from the Aitik mine. The copper grade in this deposit is muchhigher than in the Aitik mine, however it will be a much smaller operation. At the moment the aimis to have a surface mine, which can produce ore for about 5 years. After this 5 years undergroundmining is necessary. The plan is to open this surface mine in or before year X. From Figure 1.1 is clearthat the copper grade of the Aitik mine has a big decrease in that year. The copper from this satellitemine could then be used to have a higher copper production.

This study will investigate the possibility of a surface mine at a satellite deposit, 15 kilometersfrom the Aitik mine. This satellite mine will be implemented in the current processing at Aitik.

1.2. GOAL AND METHODSThe goal of this thesis can be summarized as follows:

"Establish a preliminary development plan for a satellite copper deposit with processing at the Aitik plant"

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1.3. REPORT OVERVIEW 2

To be able to reach the goal of the thesis, the following is done:

• Literature study of the geology of the area: can the assumption that the subsurface is the sameas in Aitik be validated?

• Obtain information about the current mining methods and design of the Aitik mine in order to

determine if this could be used for this satellite mine.• Determine the best option for the fragmentation of the ore by nding an optimized blasting

schedule.

• Create a production schedule for the copper ore.

• Do a basic economic evaluation of the satellite mine operations.

• Derive recommendations for mining the satellite mine.

In this studies, all economics are given in Swedish krona or SEK. In May 2014 the exchange rate is(CNN (2014 )):

Swedish krona Euro American dollar1 0,11 0,15

1.3. REPORT OVERVIEW This thesis is structured as follows. In chapter 1 the general framework and objectives of this thesisare discussed. Chapter 2 will go deeper into the region of the Aitik mine and the Aitik mine itself.Chapter 3 will be about the processing at Aitik and its limitations. Chapter 4 will cover the satellitemine with its data, assumptions and decisions. Chapter 5 will be about the production scheduleand the economic evaluation, this chapter will evaluate if the project is protable or not. Finally, in

chapter 6 conclusions are presented and in chapter 7 the recommendations are set out.


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2THE A ITIK MINE AND ITS REGIONThis chapter will go deeper into the geology of Aitik and its surrounding and it will present somecurrent data from the Aitik mine and processing site.

The Aitik mine and its region is located in the northern part of Sweden. The location is shown onthe map of gure 2.1.

Figure 2.1: The location of the Aitik mine and its region in the northern part of Sweden (McGimpsey , 2010).

2.1. GEOLOGICAL SETTING OF THE REGIONThe bedrock geology in northern Sweden is the result of a complex geodynamic evolution including repeated extensional and compressional tectonic regimes and associated magmatic and metamor-phic events ( Wanhainen et al. , 2012). The deformation in the northern Norrbotten ore provinces,the province in which the Aitik mine and its satellite mines are located, varies both regionally andon a local scale from a strong penetrative foliation to texturally and structurally well preserved rocks.The ductile deformation includes at least two phases of folding, with axial surface traces to the foldsmainly trending NW-SE and N-S. The age relationship between these two phases is not clear.

A highly saline(38 wt.% NaCl) aqueous magmatic uid was released at about 300 degrees Centi-grade and a pressure of nearly 3 kbar, forming disseminated and vein-type ore of mainly chalcopyriteand pyrite within the intrusion and in the surrounding volcanoclastic rocks. At ca. 1.88 Ga this in-trusive and mineralising event was followed by metamorphism and deformation, resulting in folding and foliation of the rocks. Extensive deformation and redistribution of metals occured at ca. 1.78 Ga.

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2.1. GEOLOGICAL SETTING OF THE REGION 4

The Aitik Cu–Au–Ag deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry typedeposit. The complex geology is shown in gure 2.2

PORPHYRY DEPOSITS A porphyry type deposit is a hydrothermal ore deposit ( Voncken and Wolf , 2011). They are depositsthat are related to intrusions that have risen to a high level in the crust. These intrusions are subvol-canic. Aqueous uids exsolve and collect in the apical part of the intrusion. Retrograde boiling canoccur in poryphyry deposits.

Upon retrograde boiling, the uids escape by hydro fracturing of the country rock. Crystallizationof remainingsilicate accelerated. Magmatic hydrothermal solutions contain dissolved metals and arerich in potassium. In this kind of deposit different suldes can be expected, including:

• Chalcocite Cu 2S

• Chalcopyrite CuFeS 2

• Bornite Cu 5FeS 4

• Molybdenite MoS 2

• Zinc may form sphalerite Z nS

• Excess Fe forms pyrite FeS 2

Figure 2.2: Geology of Northern Sweden ( Wanhainen et al. , 2012)


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2.2. THE A ITIK MINE 5

GEOLOGY OF THE SATELLITE MINEBecause of the early stage in the feasibility study, no real geological investigation has been done, i.e.no rock mechanics results are available. However, there are some references from earlier studies thatsuggest that the geology in Aitik and the satellite mine are the same. A geological study of ’GeologicalSurvey of Sweden (SGU)’ mentioned that the ore body extended all the way to the place of the satellitemine ( Danielson , 1987).

The data from gure 2.3 suggest indeed that the two ore bodies are on the same side of the faultzones. This could suggest that the two locations do indeed have the same subsurface.

Figure 2.3: Schematic west-east vertical section through Gällivare area. The Aitik ore body is not to scale. NDZ = NautanenDeformation Zone, KADZ = Karesuando Arjeplog Deformation Zone. Red = younger intrusive rock. Green = volcanoclasticrocks ( Wanhainen et al. , 2012).

Based on these two studies from Danielson (1987) and Wanhainen et al. (2012) the assumptionthat the geology at the satellite mine is the same as in Aitik is validated. That means that the data

from Aitik can be used in this pre-feasibility study.

2.2. THE A ITIK MINEThe Aitik mine is located in the northern part of Sweden, near the town of Gällivare. Aitik is the largestcopper mine in the world. The deposit consists of pyrite and chalcopyrite yielding copper, gold andsilver. The open pit is about 3 kilometers long, over 1 kilometer wide and 450 meters deep. Thedeposit was discovered in the beginning of the 1930’s, but its exploitation began in the 1960’s. Themining capacity is gradually tuned up since the large expansion in 2010 (Boliden , 2014).

Around the Aitik mine different small deposits have been found. These satellite deposits are notfar from the Aitik mine, so they could possibly be processed at theAitik processing plant. One of these

deposits is the one used for this study.Because the same rock type in the satellite mine is found, data from the Aitik mine could be used.Some basic rock properties are listed in table 2.1.

Some discontinuities are found in Aitik and could also be expected at this satellite mine. In Aitik pegmatite dikes are found, these dikes are harder than the surrounding rock and it is therefore harderto drill, which can cause delays during the drilling and blasting of the rock.

Table 2.1: Rock properties in the Aitik mine

Rock Specic Gravity 2,8Elastic Modulus 60 GPa

UCS 100 MPa


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3P ROCESSING THE COPPER OREThis chapter will cover the processing steps at the processing plant at the Aitik mine site. Before theore gets into the processing sequence, drilling and blasting have to be done, as well as loading the oreand transporting it to the processing site.

The process at the Aitik processing site is displayed in gure 3.1. The same processing site will beused for the processing of the ore of the satellite mine.

Figure 3.1: The processing process at the Aitik processing site

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3.1. CRUSHING THE ORE 7

3.1. CRUSHING THE OREThe ore of Aitik is pre-crushed in the Aitik mine itself. Afterwards a cone crusher is used as secondary crusher. Crushing is based on impact rather than on pressure. Cone crushers have a wide crushing cone with a side angle of 30 ◦ C.

The crushing action is continuous. An eccentric cone is rotated in a funnel shaped opening. Start-

ing the crusher with a full crushing chamber and a choke feed is possible. The feed can be directly dumped from a mine truck ( Chaigneau , 2011). After crushing, the ore is transported 7 kilometers by conveyor belt to the ore storage.

3.2. GRINDING AND MILLINGThere are two milling lines with a primary and a secundary mill. The capacity for each line is 2200tonnes per hour, which leads to a total of 36 million tonnes per year. The primary mills are 12 metersin diameter and 14 meters long. The motor in the primary mills has a capacity of 22.5 MW. The sec-ondary mills are 11,4 meters in diameter and 12 meters long. The motor in the secondary mill is 10MW. The feed fractions are between 25 and 100 mm and the discharge is 44 mesh(0.36 millimeters)(Metso , 2006).

The grinding circuits are fully autogenous. They are so-called because they self-grind the ore. A rotating drum throws larger rocks of ore in a cascading motion which causes impact breakage of larger rocks and compressive grinding of ner particles. A picture of the grinding circuits is shown ingure 3.2.

Figure 3.2: The Mills at Aitik

3.3. FLOTATIONIn Aitik froth otation is used. This is a method for physically separating particles based on differ-ences in the ability of air bubbles to selectively adhere to specic mineral surfaces. When these par-ticles are attached to the bubbles, they will be brought to the surface. These bubbles with its particles


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3.4. LIMITATIONS OF THE PROCESSING 8

are then removed from the otation tank ( Kawatra , 2009). This principle of otation is given in gure3.3.

Figure 3.3: Principle of otation ( Kawatra , 2009)

In Aitik there are 52 otation cells with a total volume of 5340 m 3 of otation cells. To achievebetter grades re-oating is required in one (cleaner) or more (recleaner) additional stages ( Miskovic ,2011 ). In Aitik there are different otation tanks, the ore is enriched furtherand further in these tanks.

FURTHER PROCESSING After these processing steps the concentrate is dried and stored. The concentrate will now have atarget of 60% copper. The concentrate will then be transported to the trains, which will transportthem to Boliden’s smelter in Rönnskar, a smelter near the city of Skellefteå.

3.4. LIMITATIONS OF THE PROCESSINGIn order to implement the operation of the satellite deposit at the Aitik processing site, knowing thelimitations of the crusher are important. The only limitation is the fragmentation, the ore needs tobe ne enough to be processed at the Aitik site. The crusher in Aitik can take big boulders if nec-essary. However, for the trucks it is better to not have these boulders. The aim should be to get the

fragmentation under 300 mm. Therefore either ne blasting should be considered or the ore shouldbe pre-crushed at the mine site. The evaluation of both options will be discussed in section 4.2.


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4THE SATELLITE MINEThere have been mining operations before on this location. The copper deposit was found in the late19 th century. In the early 20 th centurymining started. The communitygrew quickly, but soon enoughthe mining company went bankrupt, leaving the location to what it is today. Now you can see the oldfoundations of storages and some remnants of the copper mine of the early 1900s.

The satellite mine is located about 15 kilometers from the Aitik mine. Because of the relatively small deposit, a surface mine is being investigated as an alternative to bring forward the mining of the ore on top of an underground mine. The ore will be transported to the Aitik concentrator.

In this chapter an analysis of the satellite mine will be done, including mining methods and amine design. It will also include a comparison between blasting and pre-crushing of the ore.

4.1. A NALYSIS OF THE SATELLITE MINE

Figure 4.1: A simple model of the ore at the satellitemine

Figure 4.2: Cross section of the block model

The ore deposit of the satellite mine is a narrow, steeply dipping ore as is visible in the gures 4.1and 4.2 (Boliden Technology , 2014). This means production costs fastly increase with depth, becausethere will be more waste production. Investigation of the boreholes at the site are focused on thehigh-grade deep zone, leaving only one borehole directly adjacent to the surface mine. This meansthat there is a high uncertainty, mainly around the boundaries of the surface mine and the marginalore.

The amount of ore from the satellite mine is determined in Boliden’s Ideastudy using a block model ( Boliden Technology , 2014). The ore data can be found in table 4.1.

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4.1. A NALYSIS OF THE SATELLITE MINE 10

Table 4.1: The amount of ore in the satellite mine

ORE FROM PIT

Ore (kton) 5233

Ore Cu (%) 0.5Ore Au (g/ton) 0.2Ore Ag(g/ton) 1.3Ore NSR 170

M INING METHODTo start, a mining method has to be chosen. There are several options, having an underground mineor a surface mine. Research has been done and because of the narrow, steeply dipping formation it would be benecial to start with a surface mine. This surface mine should be fairly shallow, becausethe deeper this mine is, the more waste it will produce. The costs therefore fastly increase with depth.

There are four common surface mining methods (Darling , 2011):

• Open-pit mining

• Quarrying

• Strip mining

• Auger mining

Strip mining and open-pit mining are the two most dominant types of surface mining methods inthe world, accounting for approximately 90% of the surface mineral tonnage. Strip mining is used forlarge, tabular, at lying ore bodies for mineral seams, that are relatively close to the surface. Open-pitmining is typically applied to disseminated ore bodies for steeply dipping veins or seams where themining advance is toward increasing depth. Quarrying is a special type of open-pit mining used toproduce aggregates and dimension stone products. The last method, auger mining, is primarily usedto remove coal from under a nal highway.

This means that for the satellite mine an open-pit mine is preferred. The ore body is steeply dip-ping and therefore the open-pit is a good option. This option is also preferred, since the assumptionis that the ore is the same as in Aitik. This means the methods from the Aitik mine could be used atthis satellite mine site, i.e. it would cost less because a lot of knowledge is already there.

M INE DESIGNTo have an optimized open pit design, alternative depths of the open pit have been analyzed by Boli-den Technology (2014). The open pit mine is relatively shallow, the depth varies from 120 meters inthe south end to 60 meters toward the north end. Optimization has been done by testing a number of alternative open pit bottoms from Z355 to Z435 with a simplied design, Z355 stands for 355 metersabove sealevel and is according to the Swedish coordinate system. The optimization did also con-sider different cut-off grades, that is: values of 55 SEK and 124 SEK. The calculations can be found inappendix A.2. The optimum pit-bottom height is Z400 for a cut-off of 55 SEK and Z435 for a cut-off value of 124 SEK.

The same design criteria are used for embankments as used in the Aitik mine, but the design isslightly adjusted. The total slope will be 2 degrees steeper than in the Aitik mine. This can be done,because of the shallow open pit. A steeper slope is benecial, because it reduces the volume of the


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4.1. A NALYSIS OF THE SATELLITE MINE 11

Table 4.2: The waste reduction if a steeper slope is used

WASTE

Waste original design(kton) 10.717

Reduced waste rock with a steeper slope of 2 degrees (kton) - 1.169 Waste steep design (kton) 9.549

waste rock. The total reduction of waste rock is shown in table 4.2. This would mean that the benches would be smaller, this is possible because of the smaller equipment that is used.The total table with its assumption can be found in appendix A.1.

The maximum slope for the rock itself will be 72 ◦ , this is the same slope as in Aitik. The bench width will be between 16 and 18 meters. This leads to an overall slope of 54 ◦ .The bench heights of 10 and 15 meters have been considered. The bench height of 10 meters is cho-

sen.The total mine design is shown in gure 4.3.

Figure 4.3: The bench design of the satellite mine. Note that this drawing is hypothetical and not to scale.

CUT-OFF VALUE

The cut-off value for the NSR in the open pit mine will differ from the nal cut-off grade that will beused in underground mining. There is a difference, because all the ore and waste from the open pitmine have to be transported to the pits edges. The waste rock will later be used as backll, to ll theopen pit mine. The waste rock will be stored close to the edges of the open pit mine.There are a few cut-off options (Boliden Technology , 2014):

• A cut-off of NSR 124 SEK/ton gives 2.1 million tonnes of ore with an average NSR of approxi-mately 400 SEK and a copper grade of 1.0%

• A cut-off of NSR 55 SEK/ton gives 5.2 million tonnes of ore with an average NSR of approxi-mately 200 SEK and a copper grade of 0.5%


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4.2. FRAGMENTATION OF THE ORE 12

Table 4.3: Cut-off calculations

Cutoff Open pit Satellite mineSEK/ton

Mining − Assumes that the rock will

be mined whether its ore or waste rock.

Crushing 5,0 Possible crushing Transport to Aitik 17,5Backlling of waste rock to thepits

11,3 Back lling

Coverage −

Enrichment 27,5Theoretical cut-off Used in calculation

Cutoff NSR 39 55Copper grade 0,11% 0,15%

The cut-off grade in the calculation as shown in table 4.3 is slightly higher than the theoreticalone, because it has to be a certainty that it would be protable. From appendix A.2 is clear that themaximum result will be obtained with an elevation of Z400 for the pit bottom and a cut-off value of 55 SEK. Therefore this value will be used further in this research.

4.2. FRAGMENTATION OF THE OREIn order to process the ore at the Aitik crusher, the fragmentation should be taken into account. Thebiggest problem is not the crusher itself, but the transportation to the crusher. It’s not favourable if therocks are bigger than 300mm, thus it should beeither blasted to smaller particlesor blasted to a biggersize and crushed at the mine site. The fragmentation of 300 mm could be accomplished by making a ner blasting schedule, i.e. more emulsion in order to get the rocks ner fragmented. Anothermethod to get ner rocks is to have an in-pit crusher that pre-crushes the ore, however blasting stillneeds to be done. Both of these options are discussed.

DRILLING AND BLASTINGThe ore and waste in the satellite mine will be drilled and blasted. The needed fragmentation sizedepends on the use of an in-pit crusher or not. The costs of both possibilities are evaluated.

For the drilling and blasting the Kuz-ram model is used. This is an empirical model that uses blastdesign and rock factors in an empirical equation to predict the fragmentation size distribution.For this analysis some factors have to be chosen, such as the burden and spacing. The burden is theminimal distance from the axis of a blasthole to the free space. The spacing is the distance betweenblastholes in the same row. These parameters depend upon the drilling diameters, the properties of the rock and explosives and the height of the bench ( Jimeno et al. , 1995).

From Hardygóra et al. (2004) the value u , which determines the size distribution curve, can becalculated by the following formula:

u = [2.2 − 14B / D ]∗[((1 + S / B )/2) 0.5 ]∗[1 − E p / B ]∗[| l f − l c | / l + 0.1]0.1 ∗l H

in which D is the blasthole diameter in millimeters, B is the burden in meters, S is the spacing inmeters, l is the total charge length in meters, l f is the length of the bottom charge in meters, l c is the


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length of the column charge in meters, H is the bench height and E p is the typical deviation due todrilling.

The same emulsion as in Aitik is used, this emulsion has the properties listed in table 4.4. Together with the rock properties from section 2.2 it gives the xed parameters of the calculation.

Table 4.4: Properties of the emulsion

Explosives

Density 1 SGRelative Weight Strength 90% (% ANFO)

Nominal VOD 5500 m/sEffective VOD 5500 m/s

Explosive Strength 0,9

In the block model a bench height of 10 meters is used. The stemming is usually around 70% of

the burden according to National Park Service (1999). The stemming is the part of the borehole thatis not lled with explosives, but with a stemming material such as gravel or sand. With the blasting the aim is to have 80% of the rocks smaller than 300 mm. Another alternative is

to blast the rocks to 1200 mm and pre-crush it at the satellite mine site. Both of these options need tobe considered. The intention of this comparison is to nd the most cost-efcient blasting plan.

Using Atlas Copco (2013 ) the different drills are found with their properties, the most importantproperty is the hole range. With this diameter the amount of emulsion could be evaluated to get asize distribution that could be used for the satellite mine.

A good option for drilling and blasting is the Atlas Copco SmartROC D65, a percussive drilling machine. Other machines could be possible as well, however for this pre-feasibility study the D65 isused as a reference. This would be a typical sort of equipment that will be used in a small open-pit

operation. The maximum diameter it can drill is 203 mm. Based on this the Kuz-ram model is madeas shown in appendix A.3.The costs are based on the known costs per meter from the Aitik mine, this is a total cost of 560

SEK/m. The hole diameter of the Atlas Copco SmartROC D65 is smaller than in Aitik. Therefore thetotal costs will be an overestimate of the real costs. In table 4.5 two numbers are evaluated. First thecosts if 80% of the rocks is smaller than 300 mm and secondly the costs if 80% of the rocks is smallerthan 1200 mm.

Table 4.5: Costs for the drilling and blasting with an Atlas Copco SmartROC D65

Target size Hole diameter Charge Length Charge Density # holes Total costs

300 mm 203 mm 7,2 m 1,29 kg/ m 3 39723 160 MSEK 1200 mm 203 mm 7,2 m 0,97 kg/ m 3 29792 121 MSEK

The difference between these two fragmentation sizes is about 40 MSEK, this excludes the costsof the SmartROC D65 itself, but this will be the same for both. This means that blasting to 300 mm ismore expensive, because more drill holes are needed. However, if the rock is blasted to a size of 1200mm the rock needs to be pre-crushed by an in-pit crusher.

These costs do not include the Atlas Copco SmartROC D65 itself. The costs of this equipment willhave more or less the same price as the SmartROC D65 in Aitik, which will cost around 7 MSEK.The variables chosen for the blasting to 300 mm is given in table 4.6.


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Table 4.6: The variables used for the blasting to 300 mm

Hole Diameter 203 mmCharge Length 7,2 mBurden 4 m

Spacing 4,5 mDrill Accuracy SD 0,1 mBench Height 10 m

U SING AN IN-PIT CRUSHER An in-pit crusher can be rented, so that means a xed cost per ton is known for the operation. Thecosts for an in-pit crusher is 10 SEK/ton. Only the ore needs to be pre-crushed, the waste will bedumped on the edge of the mine, no matter what the size is. This means that about 5.2 Mton need tobe crushed. The total costs of this operation would be around 52 MSEK.

This means that the total costs for blasting to 1200 mmand then crushing it would be moreexpen-sive than blasting to 300 mm with direct transport to the Aitik processing site. Therefore the option toblast it to 300 mm is preferred.


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5P RODUCTION SCHEDULE AND ECONOMICEVALUATION

With the information of the previous chapters, a production schedule can be made. When a produc-tion schedule is made, an economic evaluation could be done. In this economic evaluation comesforward if the mining of this satellite mine is protable or not, in order to make a decision to gothrough with the project. This evaluation is done in this chapter.

5.1. PRODUCTION SCHEDULEThe satellite mine will be mined in two stages, the division of the two stages is the green line in gure5.1 (Boliden Technology , 2014 ). The decision is made to mine in two stages because the mining wouldbe faster. Now it is possible to mine at two positions at once which will increase the production.

Figure 5.1: The outline of the satellite mine

Per stage one shovel will be used, for the calculation a capacity of 1000 tonnes per hour is used.

If the rst stage is nished, the shovel that is used for it will be used in the second stage. Thus it will double the capacity in stage 2. However, the rst blast of every bench can only use one shovel,because of the available space. The other blasts can be done simultaneously and thus the two shovels

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5.1. PRODUCTION SCHEDULE 16

can be used. This all ends up in a production schedule, which is summarized in table 5.1. This wouldmean that the open-pit mine can produce for just under 6,5 years. A workweek of 2 shifts and 5 daysa week is assumed: this results in 12 hours of work a day, 5 days a week.

Table 5.1: The total amount of days to mine the two stages and its start and end date

Total duration(days) Start date End datestage 1 815 01/01/2018 26/03/2020stage 2 2340 01/01/2018 29/05/2024

In the production schedule a difference is made between the till, waste and ore. The till is mined rst,followed by the waste and ore. The till is done rst, because this is the soft soil which can be easily extracted. The waste and ore have to be blasted, because the rock is a lot harder. In the block modelthe different parts are divided in either waste or ore, so that could be mined separately. With thisinformation the production can be summarized per year, as done in table 5.2.

Table 5.2: Summary of the production per year

Year Till (kton) Void+waste (kton) Ore (kton) Copper grade % Copper tonnes NSR

2018 1.654 1.346 127 0,4 467 1702019 1.086 1.301 741 0,3 2.425 1102020 349 1.932 718 0,5 3.284 1402021 100 1.994 579 0,5 2.965 1902022 0 2.109 956 0,4 4.165 1702023 0 1.619 1.362 0,5 7.097 2002024 0 415 750 0,7 4.954 260Grand Total 3.191 10.717 5.233 0,5 25.356 170

The production per month for the rst stage is given in appendix B.1. In appendix B.2 the productionper year is given for stage 2. An overal production per bench is given in appendix B.3.

TRACE ELEMENTSBesides copper, other trace elements are found in the ore. The ones that will be processed are silverand gold.

The amount of gold and silver during the two stages and the total amount of these trace elementsis given in table 5.3. The amount of silver and gold is given in gure B.4 for the entire production of

the satellite mine.

Table 5.3: The production of the trace elements gold and silver

Stage Ore (kton) Ag (g/ton) Au (g/ton) Ag (kg) Au (kg)Stage 1 1.105 1,0 0,1 1.091 144Stage 2 4.129 1,4 0,2 5.924 976Total 5.233 1,3 0,2 7.015 1120

The processing site in Aitik is not optimized for silver and gold, therefore the recovery is pretty low. Only about 50% of the gold is retrieved from the concentrate, for silver there’s a slightly higherpercentage of approximately 65% that is recovered.


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5.2. ECONOMIC EVALUATION 17

5.2. ECONOMIC EVALUATIONUsing the production schedule an NPV calculation could be done. To do this calculation the long-term metal prices are needed. The prices that Boliden uses are listed in Boliden Technology (2013)and given in table 5.4. A troy ounce is equal to 31.10 grams.

Table 5.4: The long-term prices of copper, gold and silver

metal pricesCu $6600/ton Au $1200/tr.oz Ag $20/tr.oz

With all this data a net present value calculation can be done. The Net Present Value(NPV) of aproject is today’s cash equivalent of the cash ow that is expected to be generated by this project,assuming that money can be invested or borrowed at a specied discount rate (Rendu , 2014). The

formula for the NPV is:

NPV (i , N ) =N

t = 0

R t (1 + i )t

in which N is the total number of years, R t is the net cash ow, i is the discount rate and t is thetime of the cash ow.

The discount rate used in the NPV calculation is 10%. The enrichment at the Aitik processing sitecosts the same as for the Aitik ore. The mining costs, till extraction and mining and transport costs of the ore are based on historic knowledge of the costs in other mines, which was provided by Boliden.

An example of a NPV-calculation is given in appendix C.1. The NPV of this operation is 59,9 MSEK.

It is still an early stage in the feasibility study, but some sensibility calculations could be donebased on the NSR. The NSR of the ore depends on the long-term costs of copper, gold and silver.These prices could vary in the upcoming years. It turns out that the break-even point is around 152MSEK as shown in table 5.5.

Table 5.5: NPV Model for different NSR values

NSR NPV 150 -6.6 MSEK 151.93 0 MSEK

160 27.5 MSEK 170 61.6 MSEK 180 95.7 MSEK 190 129.8 MSEK

The project is also sensible for the exchange rate between the American dollar and the Swedishkrona. Everything in this studies is calculated in SEK, but the company gets paid in American dollars.The exchange rate could be either favourable or unfavourable and could be a factor in the economicevaluation. This calculation is not included in this studies.

An NPV model is made for different capacities. In table 5.6 the NPVis given fordifferentcapacities.If the capacity per hour is increased, the project time is decreased, and vice versa. The calculation isdone for a capacity of 500, 1000, 1500 and 2000 tonnes/hour.


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5.2. ECONOMIC EVALUATION 18

Table 5.6: NPV Model for different capacities

capacity NPV 500 tonnes/hour 7.0 MSEK 1000 tonnes/hour 59.9 MSEK 1500 tonnes/hour 53.4 MSEK 2000 tonnes/hour 58.9 MSEK

From table 5.6 is clear that a capacity of 1000 tonnes/hour is the most favourable for this project.This is the capacity that is used for this studies.


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6CONCLUSIONSThe objective of this project was to establish a preliminary development plan for for a satellite copperdeposit with processing at the Aitik plant.

As a result of this studies the following conclusions can be made.

• The geology of the satellite mine is found to be similar than in Aitik. Thus the same designproperties could be used as found in Aitik.

• An open-pit mine is the best surface mining option. A slightly steeper overall slope angle couldbe used and for the rock the same slope angle will be used as in Aitik.

• The best cut-off value is 55 SEK with a pit bottom of 400 meters and thus a pit depth of 85meters.

• It is more cost-efcient to blast the ore to 300 millimeters than to blast it to a bigger size of 1200millimeters and then pre-crush it at the satellite mine site.

• The production time of the open-pit operation is just under 6,5 years.

• The Net Present Value of the operation is 59,9 MSEK.

• An NPV model shows that the most favourable capacity for this project is 1000 tonnes/hour.

This open-pit operation is supposed to be followed by an underground operation. The ore gradein the lower part of the open-pit mine is higher than the upperpart of the mine. Therefore the averagegrade of the underground operation would probably be higher than that of the surface mine. This

could mean that the underground operation is more protable than the open-pit operation.Since this open-pit operation has a positive Net Present Value of 60 MSEK with the prospect of

an even more protable underground operation, the mining of this satellite deposit has a promising perspective.

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7RECOMMENDATIONSThis study suggests that the mining of the satellite deposit is a protable operation. However, toget more accurate results and more certainty about the project, the following recommendations aremade:

1. Evaluate the ore body more accurately by drilling more holes

The ore body model is now made with only one borehole. That means that almost all the orein this investigation is a result of extrapolating the existing data from the deeper part of the orebody to the upper part. By drilling more holes the model of the shallower part could be mademore accurate.

2. Look into the archives to nd information about the former mine in the 1920’s Since there was amine in the 1920’s it is possible that there is geological information available. This might givean indication about the deposit. It might be that there were some tests done at that time whichcould be used to make a better evaluation of the project.

3. More cut-off values could be considered

For this pre-feasibility study only the cut-offs of 55 SEK and 124 SEK are considered. For fu-ture research other cut-off grades could be considered to get the most protable model for thisopen-pit operation.

4. Investigate the possibility of decreasing the production time of the open-pit part of the mine

The length of the operation by using two shovels with a capacity of 1000 tonnes/hour is 6,5 years. The production could be faster by using longer working days, 3 shifts instead of 2 and working all days of the week, instead of 2 shifts and working 5 days a week. Another option isto use more shovels and thus increase the capacity. However, it turns out that the increase of capacity is not protable.

5. Consideration of a leaching plant as an extension of the current processing site

The recovery of gold and silver is relatively low. This recovery could be increased by using aseparate leaching plant to extract the gold and silver. Since the production of the Aitik mineitself increases, and there are also satellite mines that will increase production in the future, itmight be protable to have a leaching plant on site to recover the silver and gold.

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BIBLIOGRAPHY

Atlas Copco (2013). Blasthole Reference Book . Atlas Copco.

Boliden (2014). Aitik fact sheet. http://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdf . Last checked: 28 April 2014.

Boliden Technology (2013). Annual Report 2013 .

Boliden Technology (2014). Idéstudie 2014 Dagbrott .

Chaigneau, R. (2011). Physical Processing . TU Delft.

CNN (2014). Currency exchange rate. http://money.cnn.com/data/currencies/ . Last checked:

2 May 2014.

Danielson, S. (1987). Geologisk beskrivning över Nautanen - Aitik - Jårbokistråket i Gällivareområdet .Sveriges Geologiska Undersökning.

Darling, P. (2011). SME Mining Engineering Handbook . Society for mining, metallurgy and explo-ration, Inc., 3rd edition.

Hardygóra, M., Paszkowska, G., and Sikora, M. (2004). Mine Planning and Equipment Selection 2004 .CRC Press.

Jimeno, E. L., Jimeno, C. L., and Carcedo, A. (1995). Drilling and blasting of rocks . Geomining Tech-

nological Institute of Spain.Kawatra, S. K. (2009). Froth Flotation . Michigan Technological University.

McGimpsey, I. (2010). Petrology and lithogeochemistry of the host rocks of the nautanen cu-au de-posit, gällivare area, northern sweden. Master’s thesis, Lund University.

Metso (2006). Service contract for swedish grinding mills. http://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocument . Last checked: 8 May 2014.

Miskovic, S. (2011). An investigation of the gas dispersion properties of mechanical otation cells: an in-situ approach . PhD thesis, Virginia Polytechnic Institute and State University.

National Park Service (1999). Handbook for the transportation, and use of explosives . National Park Service.

Rendu, J.-M. (2014). An introduction to cut-off grade estimation . Society for mining, metallurgy andexploration, Inc., 2nd edition.

Voncken, J. H. L. and Wolf, K. H. A. A. (2011). Economic Minerals and Rocks - An introduction to ores,ore minerals, industrial minerals, and coal . TU Delft.

Wanhainen, C., Broman, C., Martinsson, O., and Magnor, B. (2012). Modication of a palaeoprotero-zoicporphyry-like system: integration of structural, geochemical, petrographic, and uid inclusion

data from the aitik cu-au-ag deposit, northern sweden. Ore Geology Reviews , 48:306–331.

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http://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdfhttp://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdfhttp://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdfhttp://money.cnn.com/data/currencies/http://money.cnn.com/data/currencies/http://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocumenthttp://money.cnn.com/data/currencies/http://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdfhttp://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdf


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Appendices


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A PPENDIX A: C ALCULATIONS FOR THE

SATELLITE MINE

A.1. W ASTE REDUCTION WHEN USING A 2 DEGREES STEEPER SLOPE

Table A.1: Waste Reduction Calculation

Calculation of waste that can be saved by having a steeper slope

Changing theslope from IRS50 to IRS 52saves X metersper pallet 3 m Approximateopen pit depth 90 mbench height 15 mdensity 2,8

Production of waste per yearLength of open pit kton Y2018 Y2019 Y2020 Y2021 Y2022Pall 1 437 m 110 100%Pall 2 890 m 224 60% 40%Pall 3 880 m 222 70% 30%Pall 4 820 m 207 30% 70%Pall 5 810 m 204 70% 30%Pall 6 800 m 202 80% 20%

1.169 135 417 345 223 40

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A.2. D IFFERENT ELEVATIONS CUT - OFF OF 55 SEK A ND 124 SEK

Note that the average surface elevation at the satellite mine is 485 meters.

Table A.2: Optimum pit depth calculated for two cut-off values

Low grade cutoff HG=125 LG=80 Mar=55 Avg. Pit depth (m): 100 50 85 130

Design criteria for corresponding slopes at Aitik Pit bottom elevation (m): 385 435 400 355Ore (million tonnes) 7,38 1,91 5,24 11,67Cu% 0,4 0,6 0,5 0,4

NSR SEK/ton 170 240 190 160Moraine (million tonnes) 4,34 1,54 3,19 6,43 Waste Rock (million tonnes) 16,01 4,01 10,72 28,59Total ore, waste rock and moraine 27,72 7,45 19,16 46,70

Costs and Revenues in million SEK Refractive Cost − 693 − 186 − 479 − 1167Transport & Enrichment − 369 − 95 − 262 − 584Recovery − 80 − 20 − 54 − 143Ore revenue 1283 466 996 1864Results 141 165 202 − 30

High grade Cutoff = 124100 50 85 130Design criteria for corresponding slopes at Aitik

Pit bottom elevation (m): 385 435 400 355Ore (million tonnes) 2,23 0,93 1,80 3,18Cu% 1,01 1,04 1,02 0,98NSR SEK/ton 410 430 420 400Moraine (million tonnes) 4,34 1,54 3,19 6,43 Waste Rock (million tonnes) 21,15 4,98 14,16 37,08Total ore, waste rock and moraine 27,72 7,45 19,16 46,70

Costs and Revenues in million SEK Refractive Cost − 693 − 186 − 479 − 1167Transport & Enrichment − 112 − 47 − 90 − 159Recovery − 106 − 25 − 71 − 185Ore revenue 922 398 754 1271Results 11 140 114 − 241

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A.3. K UZ - RAM MODELS FOR BLASTING TO 300 A ND 1200 MILLIMETERS

Figure A.1: The Kuz-ram model for blasting to 300 mm

Figure A.2: The Kuz-ram model for blasting to 1200 mm

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B.2. SUMMARY OF THE STAGE 2 PRODUCTION

Table B.2: Summary of the production per year for stage 2

Year Till (kton) Void + Waste (kton) Ore (kton) Ag g/ton Au g/ton Cu %

2018 636 923 5 2,1 0,4 0,82019 765 750 49 1,7 0,3 0,62020 349 1.855 427 1,0 0,2 0,62021 100 1.993 579 1,4 0,3 0,52022 0 2.109 956 1,2 0,2 0,42023 0 1.619 1362 1,5 0,2 0,52024 0 415 750 1,9 0,3 0,7Grand Total 1.851 9.667 4.129 1,4 0,2 0,5

B.3. TOTAL PRODUCTION OVERVIEW

Figure B.3: Production Schedule Summary per bench

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Figure B.4: The gold and silver grades in the satellite mine

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A PPENDIX C: ECONOMIC E VALUATION

C.1. C ALCULATION OF TH E NET PRESENT V ALUE

Table C.1: The overall NPV Calculation of the project