Amayapampa Gold Project

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Orway Mineral Consultants (WA) Pty Ltd, Level 4, 1 Adelaide Terrace, East Perth, Western Australia, 6004Tel: +61 8 6210 5601 Fax: +61 8 6210 5555 Email: [email protected] Web: www.orway.com.au A.B.N: 40 093 277 126

Report No. 8677 Rev CJanuary 2011

AMAYAPAMPA GOLD PROJECT

COMMINUTION CIRCUIT DESIGN

REPUBLIC GOLD



Republic Gold a Report No. 8677 Rev C

CONTENTS

EXECUTIVE SUMMARY ..................................................................................................................................... I

1.0 INTRODUCTION ...................................................................................................................................... 1

2.0 GEOLOGY AND TESTWORK ................................................................................................................. 2

2.1 Geology .......................................................................................................................................... 2

2.2 Testwork ......................................................................................................................................... 4

2.3 Ore Interpretation ........................................................................................................................... 6

2.4 Viscosity Analysis ........................................................................................................................... 6

3.0 PROCESS DESIGN CRITERIA ............................................................................................................... 9

4.0 POWER UTILISATION ........................................................................................................................... 10

5.0 CRUSHING CIRCUIT MODELLING ...................................................................................................... 11

5.1 Simulation & Crusher Specification .............................................................................................. 11

6.0 GRINDING CIRCUIT MODELLING ........................................................................................................ 14

6.1 Mill selection ................................................................................................................................. 14

6.2 Throughput estimates .................................................................................................................. 15

7.0 CIRCUIT SELECTION............................................................................................................................ 17

8.0 MINE SCHEDULE ORE BLENDS .......................................................................................................... 20

9.0 CONSUMABLES .................................................................................................................................... 23

10.0 CONCLUSION ........................................................................................................................................ 24

11.0 DISCLAIMER .......................................................................................................................................... 25

12.0 STANDARD WARRANTY ...................................................................................................................... 25

13.0 OWNERSHIP ......................................................................................................................................... 25

TABLES

Table 2-1 Comminution Testwork Summary ............................................................................................... 5

Table 2-2 Comparison of Testwork Results with Database ......................................................................... 6

Table 3-1 Process Design Criteria ............................................................................................................... 9

Table 4-1 Power Modelling Results ........................................................................................................... 10

Table 5-1 Crusher Specification ................................................................................................................ 11

Table 6-1 Mill Specification ........................................................................................................................ 14

Table 6-2 Throughput estimate - Tertiary Crush Ball Milling ..................................................................... 15

Table 6-3 Throughput estimate - SS SAG ................................................................................................. 15

Table 6-4 Performance of Various Feed Types through SAB ................................................................... 15

Table 9-1 Liner and Grinding Media Consumption .................................................................................... 23



Republic Gold b Report No. 8677 Rev C

FIGURES

Figure 2-1 Comminution sample - Fresh rocks ............................................................................................. 3

Figure 2-2 Rheology Measurements for the Fresh Ore Sample ................................................................... 7

Figure 2-3 Rheology Measurements for the Transition Ore Sample ............................................................ 7

Figure 2-4 Rheology Measurements for the Oxide Ore Sample................................................................... 8

Figure 5-1 Primary Crushing Option ........................................................................................................... 12

Figure 5-2 Tertiary Crushing Option ........................................................................................................... 13

Figure 6-1 Throughput estimates ................................................................................................................ 16 Figure 7-1 Simplified flowsheet: Tertiary crush – ball milling option ........................................................... 17

Figure 7-2 Simplified flowsheet: Single Stage SAG mill ............................................................................. 18

Figure 7-3 Simplified flowsheet: SAB circuit ............................................................................................... 19

Figure 8-1 Ore type contribution to mill feed ............................................................................................... 20

Figure 8-2 Tertiary crush ball milling option – blend power requirements .................................................. 20

Figure 8-3 SS SAG milling option – blend power requirements ................................................................. 21

Figure 8-4 SAB option - SAG mill – blend power requirements.................................................................. 21

Figure 8-5 SAB option - ball mill – blend power requirements.................................................................... 22



Republic Gold i Report No. 8677 Rev C

EXECUTIVE SUMMARY

OMC was requested to undertake a comminution circuit design for the Republic Gold Amayapampa Projectin the South-West region of Bolivia between Oruro and Potosi Cities.

The target throughput provided for this project is 2.74 Mtpa or 340 tph equivalent and a grinding product P80

of 150 µm.

The testwork was completed on samples that represent the three main ore types that will be treated atAmayapampa. The mill design was based on the Fresh ore only with throughput estimates made for theother two ore types. The following table summarises the ore characteristics.

Parameter Unit Oxide Ore Transition Ore Fresh Ore

UCS MPa 27 29 40

Crushing Work Index kWh/t - - 5.5

Abrasion Index 0.249 0.1683 0.1093

Bond Ball Mill Work Index kWh/t 7.9 13.0 15.2

Bond Rod Mill Work Index kWh/t 11.4 12.3 15.2

Ore SG 2.63 2.60 2.79

Breakage Characteristics (A x b) 61.6 93.4 52.4

Three circuit configurations were considered, namely three stage crushing followed by single stage ballmilling, single stage SAG milling and SAG – ball milling. The major equipment selected for this project is asfollows:

Crushing equipment

Parameter Unit Primary Tertiary

Primary CrusherModel Metso C125 or equivalent Metso C125 or equivalentNumber of Crushers 1 1Installed Power kW 160 160Secondary Crusher

Model HP800 –or equivalentCavity Std MediumNumber of Crusher 1Installed Power kW 600Tertiary CrusherModel HP800 –or equivalentCavity Short Head MediumNumber of Crusher 1Installed Power kW 600



Republic Gold ii Report No. 8677 Rev C

Grinding Equipment

Parameter UnitTertiaryCrush

SS SAG SAB

SAG MillMill Diameter (Inside Shell) m 7.92 6.71Effective Grind Length (EGL) m 6.40 5.25Imperial ft x ft 26.0 x 21.0 22.0 x 17.1Recommended Installed Power kW 7,300 4,000

Ball MillMill Diameter (Inside Shell) m 5.49 4.88Effective Grind Length (EGL) m 9.75 7.62

Imperial ft x ft 18.0 x 32 16.0 x 25.0Recommended Installed Power kW 5,000 2,850

The following graph summarises the throughput expected on the individual ore types.

!" #!

Discussion

The tertiary crush – ball mill option generally results in the most stable milling operation with the least risk ofthroughput and grind excursions. If this option is considered and the oxide component of the resource issubstantial, then it is recommended that the materials handling properties of the oxide ore be evaluated.This will ensure that there is minimal sticky clay associated with this ore that will be detrimental to theperformance of the three stage crusher plant. The capital cost associated with a three stage crusher plant isoften higher than for the other options

The single stage SAG milling option provides a lot of flexibility when treating variable ore types. For soft oresit can be set up to operate at high ball charge and low speed, while for the more competent ores a lower ball

charge and higher speed will be required. It is however important to realise that it is not possible to changefrom one scenario to the other on a daily basis and the mine schedule should be reviewed if this option isconsidered. SS SAG milling provides good expansion options, but also requires reasonably skilledoperators.



Republic Gold iii Report No. 8677 Rev C

The SAB option is a good compromise between the ball milling and the SS SAG milling options. The ore

variability showed that the circuit becomes SAG mill limited in some cases and ball mill limited in others.Again, reasonably skilled operators are required to run the circuit efficiently.

Rheology testwork indicated that viscosity should not pose any difficulties in the comminution circuit;however more extreme viscosities were measured on fine samples at 70% solids. It is stronglyrecommended that this phenomenon be investigated and understood to avoid any potential downstreampumping and processing issues



Republic Gold 1 Report No. 8677 Rev C

1.0 INTRODUCTION

Paul Pyke of Republic Gold requested OMC to undertake a comminution circuit design for the RepublicGold Amayapampa Project in the South-West region of Bolivia between Oruro and Potosi Cities.

OMC have had previous involvement with the project (OMC Report number 8503 - March 2010).Additional comminution testwork has since been conducted to increase the confidence in the circuitdesign. The circuit selection is based on samples that were selected to represent the various oxidationstates of the Amayapampa ore. OMC has been informed that additional variability samples will besourced to further validate the design.

The target throughput is 2.74 Mtpa or 340 tph at a grinding product of 80% passing 150 µm.

This report covers:

• A review of testwork conducted

• Ore interpretation based the testwork data and a regional geological description;

• A comminution circuit design based on the process design criteria provided;

• Major equipment specifications;

• Process description and engineering design brief to allow costing;

• Recommendations for any further work to reduce the design risk.




2.0 GEOLOGY AND TESTWORK

2.1 Geology

Based on the information provided by the client, the three main ore types are classified as follows:

Oxide Zone:

Fractured – very fractured black/grey shale with bleached zones that include zones with abundant sandgrains. Fractures in filled with clay and iron oxides (limonite). Some sandstones contain sideriticcarbonate cement with abundant box works. The quartz veins show fracture filled with iron oxides andbox works. The thickness of this zone varies up to 35 m.

Transition Zone:

Fractured – massive black/grey shales with bleached zones. Also, layers of fine grain silicifiedsandstones. The pyrite content is less 1% that occurs in fine grain or euhedral crystals. The fracturesare in filled with clay and iron oxide. Quartz veins with oxide and less sulphide (pyrite).

The thickness of this zone is irregular because there are different levels between the surfaces, up to 110m.

Fresh Zone:

Broken, foliated and massive black /gray shales – sandstones shales. Pyritic black shales withsingenetic sulphides. Some sandstones contain sideritic carbonate cement pyritized and less barite,pyrite in veins, veinlets and disseminated and occurrence of quartz-sideritic veins. Authigenic pyrite,

coarse grained and euhedral arsenopyrite.




Figure 2-1 Comminution sample - Fresh rocks

The following additional commentary was provided by the site geologist (e-mail dated 3/12/2010):

The Pyrite crystals are common in black shales that are related to deep deposits in the sea. In this casemost of the rocks that are located in the Paleozoic belt in Bolivia (that correspond exactly with thepollymetallic belt) are silicoclastic sequences constituted by shales, black shales and sandy shales,depending of the depth where they were deposited. For example in Amayapampa we have anOrdovician sedimentary sequence where one can see different members, some of them with moreorganic material (graphitic), other sectors with more sand and other sectors with only shales.

There are thus two types of pyrite based on the source: the first one, related with the environment ofdeposition - in this case what the mineralogist used to call singenetic related to euxinic conditions. In

general they are euhedrals (cubics) and used to leave prints or cubic open spaces that are called boxworks. This type of Pyrite, in general don´t have interest for mineralization. There is a second type ofPyrite that it is related with the mineralization called hydrotermal pyrite. This type of pyrite is associatedwith the base metals / Au / and as a gangue with the quartz. In general this type of pyrite it is noteuhedral, but subhedral to anhedral. This pyrite fills fractures and also is disseminated in the sandyfractions and has more economic interest.




2.2 Testwork

Metallurgical test work was completed by Amdel Laboratories in Adelaide and the University of SouthAustralia on oxide, transition and fresh ore samples. The results of this work are reported in Appendix 2.

OMC have had no input into the metallurgical sample selection and are unable to comment on therepresentivity of these samples. OMC did however specify which comminution tests were required fordesign.

The selected samples were subjected to the following testwork:

• Unconfined compressive strength, UCS

• Impact crushing work index, CWi

• Abrasion index, Ai

• Bond rod mill work index, RWi

• Bond ball mill work index, BWi

• JK Drop Weight Test, JK / SMC Test

• Rheology testwork

No variability testwork has yet been carried out.

Table 2-1 summarises the comminution testwork results.




.

Table 2-1 Comminution Testwork Summary

Parameter Unit Oxide Ore Transition Ore Fresh Ore

UCS

Average MPa 27 29 40

Range MPa 0 - 45 0 - 42 13 - 66

Crushing Work Index kWh/t - - 5.5

Abrasion Index 0.249 0.1683 0.1093

Bond Ball Mill Work Index

F80 µm 2144 1937 2462

P80 µm 77 79 80

Grindability g / rev 2.75 1.56 1.25

Wi kWh/t 7.9 13.0 15.2

Closing screen µm 106 106 106

Bond Rod Mill Work Index

P80 µm 886 915 864

Wi kWh/t 11.4 12.3 15.2

RWI:BWI 1.44 0.95 1.00

Ore SG 2.63 2.60 2.79

Breakage Characteristics

A x b 61.6 93.4 52.4

A 56.5 63.1 57.6

b 1.09 1.48 0.91

DWi kWh/m 4.27 2.78 -

ta 0.61 0.93 0.73

The breakage characteristics of the Oxide and Transition material are not what would typically beexpected. Typically the oxidised ore is less competent than the transition and Fresh ore, but for theAmayapampa samples tested the oxide samples are more competent than the Transition ore. The BWivalues follow a more typical sequence.

It is recommended that this competency be verified once the variability samples have been sourced.




2.3 Ore Interpretation

Table 2-2 compares the testwork results for the oxide, transition and fresh ore with OMC’s database.

Table 2-2 Comparison of Testwork Results with Database

Parameter Percentile Rank of Data

Units Oxide Ore Transition Ore Fresh Ore

Rod Mill Work Index % Rank 10 13 34

Ball Mill Work Index % Rank 3 23 43

Abrasion Index – Ai % Rank 48 34 23

UCS % Rank 9 10 15

JK Appearance Function

A x b NOTE % Rank 71 89 63

ta % Rank 66 82 75

NOTE: For the A x b values a higher rank implies a softer ore.

The ore types are considered below average in terms of competency (A x b) as well as grindingrequirements (RWi and BWi). Abrasion indices are below average and liner and media consumptions arenot expected to be excessive.

2.4 Viscosity Analysis

A laboratory was supplied with fresh, transition and oxide ore samples ground to a P80 of 80 m,79 m and 77 m respectively for rheology testwork. Viscosity measurements were taken for each of thesamples at slurry densities varying between 50% solids and 70% solids. Standard plots of apparentviscosity (Cp) against shear rate (s

-1) for each sample are presented in Figure 2-2 to

Figure 2-4.




$

$

$

%

%

%

Approximate Limitof Centrifugal

Pumps

HighViscosity

CyclonesPumpsAgitators

Figure 2-2 Rheology Measurements for the Fresh Ore Sample

$

$

$

%

%

%

Approximate Limi tof Centrifugal

Pumps

HighViscosity


Figure 2-3 Rheology Measurements for the Transition Ore Sample




$

$

$

%

%

%

Approximate Limitof Centrifugal

Pumps

HighViscosity


Figure 2-4 Rheology Measurements for the Oxide Ore Sample

The rheology plots for each ore sample consistently suggests that while the viscosity at 60% solids isconsidered high, it should still pose no difficulty in the comminution circuit where a coarser particle sizedistribution is likely to relieve potential viscosity issues.

All of the ore samples tested exhibit more extreme viscosity at 70% solids suggesting pumping andprocessing difficulties downstream of the comminution circuit at this density. This severe increase inviscosity is surprising, and it is strongly recommended that the cause of the increased viscosity andinfluence of density be investigated in more detail.




3.0 PROCESS DESIGN CRITERIA

The process design criteria for this project is summarised in Table 3-1.

Table 3-1 Process Design Criteria

Parameter Unit Value Source

Crushing CircuitThroughput tpa 2,737,500 Client

tph 521 ClientAvailability % 60.0 Client

h/a 5,256 Client

Grinding CircuitThroughput tpa 2,737,500 Client

tph 340 ClientAvailability % 92.0 Client

h/a 8,059 Client

Grinding Product P80 µm 150 Client

Ore Parameters Crushing Work Index, CWi kWh/t 5.5 TestworkBond Ball Mill Work Index, BWi kWh/t 15.2 TestworkBond Rod Mill Work Index, RWi kWh/t 15.2 TestworkAbrasion Index 0.1093 Testwork

Ore SG 2.79 Testwork

Breakage CharacteristicsA x b 52.4 TestworkA 57.6 Testworkb 0.91 TestworkDWi kWh/m 5.99 TestworkTa 0.73 Testwork

The following circuit options were considered:

• Tertiary Crushed - Ball Mill (Tertiary Crush)

• Primary Crushed SS SAG (SS SAG)

• Primary Crushed SAB (SAB)




4.0 POWER UTILISATION

Power modelling was carried out to determine the grinding efficiency and power consumption expectedfor each configuration. Results are summarised in Table 4-1.

Table 4-1 Power Modelling Results


SS SAG SAB

Feed Rate tph 340 340 340Feed Size, F80 mm 10 125 125Product Size, P80 µm 150 150 150

Specific Crush Energy from 150mm toF80

kWh/t 0.41 0.01 0.01

SAG Milling Specific Energy kWh/t - 15.9 9.1Ball Milling Specific Energy kWh/t 12.7 - 6.8Total Circuit Specific Energy kWh/t 13.1 15.9 15.9fSAG 1.23 1.23

Grinding Power Required- SAG Mill kW - 5,406 3,094- Ball Mill kW 4,305 - 2,311- Total kW 4,305 5,406 5,405

Power modelling suggests that Tertiary crushing will be the most energy efficient option which is notuncommon. Historically, this is counterbalanced by the likelihood that tertiary crushing is more costly tobuild than the other options and incurs higher maintenance costs.

None of the primary crushed options are clearly superior from a power efficiency point of view; thereforecircuit selection will be driven by differences in:

• Capital and operating cost

• Company preference

• Relative complexity and ease of operation

• Likelihood of expansion




5.0 CRUSHING CIRCUIT MODELLING

5.1 Simulation & Crusher Specification

Two crushing circuits were designed to match the comminution circuit options. Specifically, they were:

• Primary Crushing Circuit – designed as the front end crushing for the SS SAG and SAB options

• Tertiary Crushing Circuit – designed as the front end crushing for the tertiary crush – ball millingoption

The configuration of the Primary and Tertiary crushing circuits simulated are presented in Figure 5-1 andFigure 5-2. The crusher specifications simulated are presented in Table 5-1.

Table 5-1 Crusher Specification

Parameter Unit Primary Tertiary

Primary CrusherModel Metso C125 or equivalent Metso C125or equivalentNumber of Crushers 1 1Feed Opening mm 1,250 x 950 1,250 x 950Closed Size Setting mm 130 125Installed Power kW 160 160

Secondary CrusherModel HP800 –or equivalent

Cavity Std MediumNumber of Crusher 1Feed Opening mm 267Closed Size Setting mm 33Installed Power kW 600

Tertiary CrusherModel HP800 –or equivalentCavity Short Head MediumNumber of Crusher 1Feed Opening mm 92Closed Size Setting mm 16Installed Power kW 600

It should be noted that the design is based on the assumption (client advice) that the material will flowfreely without any sticky clays. If this is not the case, the crusher design must be revised.




Figure 5-1 Primary Crushing Option



Republic Gold 13

Figure 5-2 Tertiary Crushing Option




6.0 GRINDING CIRCUIT MODELLING

6.1 Mill selection

Grinding mill equipment sizing were conducted to estimate mill specifications that would deliver the requiredthroughput. Table 6-1 details the mill specification for the three circuit configurations.

Table 6-1 Mill Specification


SS SAG SAB

SAG MillMill Diameter (Inside Shell) m 7.92 6.71Effective Grind Length (EGL) m 6.40 5.25

Imperial ft x ft 26.0 x 21.0 22.0 x 17.1L : D Ratio 0.81 0.77

Discharge Arrangement Grate GrateLiner Type Steel SteelNew Liner Thickness mm 100 100Backing Rubber mm 6 6Operating Mill Speed %Nc 75 75

Speed Range %Nc 60 - 80 60 - 80

Ball Charge- Operating % Vol 11 12- Maximum % Vol 18 15

- Ball Size Recommendation mm Up to 125 Up to 125Total Load- Operating % Vol 25 25- Maximum % Vol 35 35Pinion Power- Operating kW 5,400 3,100- Maximum kW 6,900 3,800Recommended Installed Power kW 7,300 4,000

Ball MillMill Diameter (Inside Shell) m 5.49 4.88Effective Grind Length (EGL) m 9.75 7.62Imperial ft x ft 18.0 x 32 16.0 x 25.0L : D Ratio 1.78 1.56

Discharge Arrangement Overflow OverflowLiner Type Rubber RubberNew Liner Thickness mm 100 80Backing Rubber mm 6 6Operating Mill Speed %Nc 75 75

Ball Charge- Operating %Vol 30 30- Maximum %Vol 35 35- Ball Size Recommendation mm 80 50Pinion Power- Operating kW 4,300 2,400- Maximum kW 4,730 2,680Recommended Installed Power kW 5,000 2,850




6.2 Throughput estimates

In order to make a more complete comparison of the options, each comminution configuration was re-simulated for the oxide and transition ore. These results are presented in Table 6-2 to Table 6-4.

Table 6-2 Throughput estimate - Tertiary Crush Ball Milling

Parameter Unit Fresh Oxide Transition

Feed Rate tph 340 700 415BWi kWh/t 15.2 7.9 13.0RWi kWh/t 15.2 11.4 12.3Feed Size, F80 mm 10 10 10Product Size, P80 µm 150 150 150

SG 2.79 2.63 2.60

Product of Efficiency Factors 1.163 1.004 1.101Corrected Ball Milling Specific Energy kWh/t 12.7 6.1 10.3

Ball Mill Power Required kW 4,300 4,265 4,260NOTE: The oxide throughput will probably be restricted to less than the value indicated by factors other than themil. Other probable bottlenecks include: crush circuit limitations, discharge pumps and cyclones and otherdownstream circuit constraints.

Table 6-3 Throughput estimate - SS SAG



SAG Milling Specific Energy kWh/t 15.9 10.8 11.6

SAG Mill Power Required kW 5,400 4,700 NOTE 4,700 NOTE NOTE: The SS SAG mill may be required operate at 60%Nc and high ball charge when treating oxide andtransition ore.

Table 6-4 Performance of Various Feed Types through SAB



SAG Milling Specific Energy kWh/t 9.1 7.6 5.2Corrected Ball Milling Specific Energy kWh/t 7.1 3.2 6.4

Total Circuit Specific Energy kWh/t 16.2 10.8 11.6

SAG Mill Power Required kW 3,100 3,100 1,955Ball Mill Power Required kW 2,400 1,300 2,400

Total Power Required kW 5,500 4,400 4,482

Throughput in the SAB option is limited by the SAG mill for the oxide (A x b = 61 and BWi = 7.9 kWh/t) whilethe Transition ore is limited by the ball mill (A x b = 93 and BWi = 13 kWh/t).




Figure 6-1 graphically represents the throughput estimates for each configuration and ore type.

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Figure 6-1 Throughput estimates




7.0 CIRCUIT SELECTION

Tertiary Crushed – Ball Miling

For this option, the ROM ore will be tertiary crushed to 80% passing 10mm prior to being fed to a singlestage ball mill for grinding. The ball mill will be operated in closed circuit with hydro-cyclones. The cycloneoverflow at the target grind size will report to downstream processing and the coarse cyclone underflow willrecycle back to the ball mill for further grinding.

The major concern for a tertiary crushing plant would be the clay content when processing Oxide ore as itcould cause blockages in the crusher, screens, chutes and fine ore storage. However, the client confirmedthat from visual inspection, the clay content is unlikely to be an issue for the tertiary crushing circuit.

Ball milling is considered a low risk option, but the three stage crushing plant and fine ore storage oftenresults in the highest capital cost.

A basic circuit flowsheet is shown in Figure 7-1.

Figure 7-1 Simplified flowsheet: Tertiary crush – ball milling option




Primary Crushed – SS SAG Milling

For this option, the ROM ore will be primary crushed by a jaw crusher to provide a coarse crushing productfor single stage SAG milling. The SAG mill will be in closed circuit with hydro-cyclones.

Due to the average competency (A x b = 52.4) of this ore, recycle crushing should not be required. It ishowever recommended to allow for future installation of recycle conveyors and/or recycle crushing ifrequired.

The single stage SAG mill is the most flexible of the grinding configurations for the particular ore typestested. It should however be set up to allow for high ball charge operation when the soft ores are treated.The required speed range (60 – 80% critical speed) is also extremely important to ensure that the mill can beoperated at low speed and high ball charge when treating soft ores (typically ball mill operation), and highspeed with a lower ball charge when treating the more competent ores (typical SAG mill operation).

If future expansion is a consideration, the single stage SAG mill configuration provides the simplestexpansion with future addition of a ball mill to increase throughput if the primary crusher is also adequatelysized.

A basic circuit flowsheet is shown in Figure 7-2.

Figure 7-2 Simplified flowsheet: Single Stage SAG mill

Depending upon environmental conditions, a fine ore bin is sometimes preferable to a stockpile to preventfeeding issues from frozen ore stocks.




SAB Configuration

The primary crushed product will be fed into a SAG mill, which operates in open circuit. The SAG millproduct will combine with the ball mill product prior to classification by hydro-cyclones. The cyclone overflowat target grind size will report to the downstream process, and the coarse cyclone underflow will report to theball mill for further grinding.

SAB circuits are generally considered easier to operate than single stage SAG mill. In the case of the threeore types tested, this circuit becomes ball mill limited when treating Transition ores and SAG mill limited foroxides.

These circuits are typically operated at very low ball charge in the SAG mill when treating soft ores(Transition ore in this case), with most of the comminution being done in the ball mill. As the competencyincreases, the SAG ball charge and speed is increased, allowing for more work being done in the SAG.

As with the single stage option recycle crushing should not be required. It is however recommended to allowfor the future installation of recycle conveyors and/or recycle crushing if required.

The basic circuit is shown in Figure 7-3.

Figure 7-3 Simplified flowsheet: SAB circuit

As with the SS SAG option, the stockpile can be replaced with a fine ore bin in environmental conditions thatcan often result in frozen ore stocks.




8.0 MINE SCHEDULE ORE BLENDS

An indicative first pass mine schedule has been provided to OMC to evaluate the affect of the ore blend oneach circuit option. Figure 8-1 depicts the mill feed blend.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81

% C

o n t r i b u t i o n t o m i l l f e e d

Month

Oxide % Transitio n % Fresh %

Figure 8-1 Ore type contribution to mill feed

The pinion power requirement for each monthly blend was calculated for each option. The realisticallysustainable minimum and maximum pinion power for the selected equipment was also calculated to

establish whether the required power is achieved within the typical operating range.

Tertiary crush – ball milling option

Figure 8-2 shows that the ball mill will be required to operate at very low ball charges (<20%) during the first10 months. Operating at such low ball charges results slurry pooling and thus in poor power efficiency.Over-grinding may occur during this period. The ball charge will be increased gradually to compensate forthe increase in competency.

& & & & & & & &

'( ) * + '( , % + -! '( , % + -!

Figure 8-2 Tertiary crush ball milling option – blend power requirements




SS SAG

The power requirements for the ore blend for a single stage SAG circuit is shown in Figure 8-3. It isexpected that the mill be operated at slow speed (60% Nc) initially. The speed and subsequently the ballcharge will be increased as the ore competency increases.

& & & & & & & &

'( ) * + '( , % + -! $ % . %/-

'( , % + -!$ % 0 %/-

Figure 8-3 SS SAG milling option – blend power requirements

SAB

For the SAB circuit, the SAG mill and ball mill power requirements were evaluated separately. The SAG mill

will initially operate at low ball charge and low speed, which will be increased as the competency increases.

& & & & & & & &

' ( ) * + ' ( , % + - ! $ % . %/-

'( , % + -!$ % . %/-

Figure 8-4 SAB option - SAG mill – blend power requirements

The ball mill is expected to operate at low ball charge during the first few months. In the SAB circuit thiscould however be managed by reducing the ball charge in the SAG mill even more (operating the SAG as apulper), thus increasing the power required from the ball mill.




& & & & & & & &

'( ) * + '( , % + -! '( , % + -!

Figure 8-5 SAB option - ball mill – blend power requirements




9.0 CONSUMABLES

Table 9-1 presents the calculated mill liner and media consumption rates for three of the options.

Table 9-1 Liner and Grinding Media Consumption

Unit Tertiary Crush SS SAG SAB

Primary Crusher

Liner Consumption – Fixed Jaw hours 2,400 2,200 2,200

Liner Consumption – Moving Jaw hours 3,400 3,100 3,100

Power Consumption kWh/t 0.07 0.08 0.08

Secondary CrusherLiner Consumption hours 5,700

Power Consumption kWh/t 0.30

Tertiary Crusher

Liner Consumption hours 4,600

Power Consumption kWh/t 0.32

SAG Mill

Ball Consumption 0.54 0.31

Steel Liner Consumption 0.09 0.05

Gross Power (kWh/t) 17.2 9.8

BALL MILL

Ball Consumption kg/t 0.54 0.29

Steel Liner Consumption kg/t 0.07 0.04

Gross Power (kWh/t) kWh/t 13.7 7.4

Steel liner consumption does not include waste factor, which could be as high as 30% for mill liners.




10.0 CONCLUSION

• The testwork was completed on samples that represent the three main ore types that will betreated at Amayapampa.

• The mill design was based on the Fresh ore only with throughput estimates made for the other twoore types.

• Three circuits were evaluated, tertiary crush – ball milling, single stage SAG milling and SAG – ballmilling.

• The tertiary crush – ball mill option generally results in the most stable milling operation with theleast risk of throughput and grind excursions. If this option is considered, then it is recommendedthat the nature of the oxide ore be evaluated carefully to ensure that there is minimal clayassociated with this ore. Sticky ore will be detrimental to the three stage crusher plant. The capital

cost associated with the three stage crusher plant is often higher than for the other options

• The single stage SAG milling option provides a lot of flexibility when treating variable ore types.For soft ores it can be set up to operate at high ball charge and low speed, while for the morecompetent ores a lower ball charge and higher speed will be required. It is however important torealise that it is not possible to change from one scenario to the other on a daily basis and the mineschedule should be reviewed if this option is considered. SS SAG milling provides good expansionpotential, but also requires reasonably skilled operators.

• The SAB option is a good compromise between the ball milling and the SS SAG milling options.The ore variability showed that the circuit becomes SAG mill limited in some cases and ball milllimited in others. Again, reasonably skilled operators are required to run the circuit efficiently.

• Rheology testwork indicated that viscosity should not pose any difficulties in the comminutioncircuit, however more extreme viscosities were measured on fine samples at 70% solids. It isstrongly recommended that this phenomenon be investigated and understood to avoid anypotential downstream pumping and processing issues.



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The material and advice produced by OMC as contained in this report is for the internal use of the client onlyand OMC takes no responsibility and accepts no liability for the use of or reliance upon any such material oradvice by any third party. Should a third party suffer any loss or damage as a result of using or relying uponsuch material or advice, OMC shall in no way be liable to the client or the third party.

12.0 STANDARD WARRANTY

Orway Mineral Consultants warrants that it will perform the Services in accordance with standards of careand diligence normally practised by recognised engineering consulting firms in performing services of asimilar nature. If during the one (1) year period following completion or termination of the Services, it isshown that there is error in the report or Services as a result of those standards not having been met, andyou have promptly notified Orway Mineral Consultants in writing of such error, Orway Mineral Consultantsshall perform on a reimbursable basis but without any additional fees, such corrective services as may be

necessary within the original scope of Orway Mineral Consultants Services to remedy such error. Thiswarranty shall constitute Orway Mineral Consultants sole liability with respect to the Services or anyinformation or report supplied to you. Acceptance of our report or use of any of the Services or informationshall constitute a release and agreement to defend and indemnify Orway Mineral Consultants from andagainst all other liabilities arising.

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This report, together with all intellectual property contained or embodied therein remains the property ofOrway Mineral Consultants, subject only to an express written agreement with the client to the contrary.

Prepared by ORWAY MINERAL CONSULTANTS (WA) PTY LTD:

John Baines

Lead Metallurgist

Countersigned by:

Fred Kock

Principal Metallurgist

-Orway Mineral Consultants (WA) Pty Ltd, 2010

Amayapampa Gold Project

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