UG-2 ore variability5 June 2009

Dr MAW Bryson, Mr N V Ramlall, Mr A McKenzie, Mr P Morgan (DRA)

Council for Mineral Technology

Outline

Presentation Outline

1. Variability drivers

2. Database examples of UG-2 variability

with respect to flotation & milling

3. Concluding remarks

Project feasibility studies

Geological reserve(discount

geological losses)

Mining method

Metallurgical work

Factors•Comminution loss

•Flotation loss

Converting into a reserve

1. Scoping tests

2. Pre-feasibilityØ Variability study

3. FeasibilityØ Bulk sample study

1. Head grade

2. Waste dilution

3. Degree of weathering

4. Degree of alteration

5. Blasting and mining methods

6. Proximity to geological features

Ø Footwall rock types i.e. IRUP, PEG, PRX, ANS, etc

Ø Faults

Ø Intrusions

Ø Lineaments

7. Geographical location i.e. Western/Eastern Limb

Drivers of variability in UG-2 ores

Consequences of variabilityØ Important for determining metallurgical parameters like recovery and

grade across a deposit

Ø Important for determining the payback period for a mine

Ø Milling rates for e.g. waste dilution can reduce throughput by 40 %

Ø Possible to identify problematic/good areas in a deposit

Variability methodology

Sam

plin

g M

etho

dolo

gy

Metallurgical testw

ork

Cost versus complexity of study

Examples

Examples of three Eastern Limb UG-2 ores

Ore No.1

Ore No.1 cont…

0

1

2

3

4

5

≤78 >78<82 >82<86 >86<90 ≥90

4E Recovery/ [%]

Freq

uenc

y of

occ

uren

ce Composite recovery 83 %

Ore No.2Zone

compositesZone drill cores

Bulk composite

Zone composites

Bulk composite

Ore No.2 cont…

0

1

2

3

≤87 88 89 90 91 92 93 ≥943E Recovery/ [%]

Freq

uenc

y of

occ

uren

ceBulk composite recovery 93 %

Ore No.3

Ore No. 3 cont…

0

1

2

3

4

5

≤74 >74<78 >78<82 >82<86 >86<90 ≥904E Recovery/ [%]

Freq

uenc

y of

occ

uren

ce

Examples

Examples of two Western Limb UG-2 ores

Ore No.4

Ore No.4 cont…

Site B composite recovery 84 %

0

2

4

6

8

10

12

14

≤74 >74<78 >78<82 >82<86 >86<90 ≥903E Recovery/ [%]

Freq

uenc

y of

occ

uren

ceSite A Site B

Site A composite recovery 75 %

Site B composite recovery 84 %

• Site A and Site B were characterised into altered an unaltered samples

• The presence of large amounts of talc, chlorite, serpentine, amphibole

and mica indicate some degree of alteration

Ore No.4 cont…

0123456789

10

≤70 >70<74 >74<78 >78<82 >82<86 >86<90 ≥903E Recovery [7 min]/ [%]

Freq

uenc

y of

occ

uren

ce "Altered samples" "Unaltered samples"

Ore No. 5 – Area composite

Ore No. 5 – Area composite cont…

0

1

2

3

≤75 76 77 78 ≥793E Recovery/ [%]

Freq

uenc

y of

occ

uren

ce

Ore No. 5 - Lithologies

Ore No. 5 – Lithologies cont…

0

10

2030

40

50

60

7080

90

100

Pyroxenite Anorthosite Iron-rich upperpyroxenite

Pegmatoidalpyroxenite

Lithology

3E R

ecov

ery/

[%]

Central zone Eastern Zone

Lithology composite recovery 73 %

Milling variability

UG2 ROM Size Ditributions

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

0.01 0.10 1.00 10.00 100.00 1000.00

Size,mm

%w

t Pas

sing

Milling Variability cont…

Variable top size

Size/ [mm]

%w

t Pas

sing

UG-2 ROM Size Distribution

Western LimbØ Ore body Variability affects grind and therefore recovery

Ø Example- Typical finite recovery-grind curve

82

84

86

88

90

92

35 45 55 65 75 85% -75 m

Fini

te R

ecov

ery/

[%]

μ

Eastern Limb• Waste rock generally harder than on Western Limb; and higher variability

encountered• Example- Eastern Limb ‘waste fraction’ effect on ROMB grinding

efficiency

• Indicates 40 % slowdown in breakage at high waste levels!

0.0

0.2

0.4

0.6

0.8

1.0

1.2

25 30 35 40 45

% Waste in feed

Rel

ativ

e sp

ecifi

c ra

tes

of

brea

kage

UG2 Grinding cont…•Bi-modal nature of ore is significantly affected by variations in ‘waste’ dilution

5

10

15

20

25

30

35

10 100 1000 10000 100000

Size/

Wor

k In

dex/

[kW

h/t]

Footwall Chromatic reef

[μm]

Point of cross over reflecting more energy for liberating at grain size

Grind Variation- Typical Western Limb UG2

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11

Sample ID

Com

posi

tion/

[%]

Reef Pyroxenite Norite Other

73.91.026Composite71.90.9121178.61.145976.31.053877.01.088767.40.957670.71.070571.41.078469.41.030377.21.283271.81.081173.50.98175.31.01910

(Control)

Actual% -75 µm

Relative Grindκn/κcontrol_avg

Sample №

Concluding remarks• Allocate more resources to understand the inherent variability in a

deposit

• Formulate a standard metallurgical variability methodology

• Use the methodology to understand what factors control variability

within a deposit

Thank youwww.mintek.co.za