1) Mineralogical studies and leaching tests are important for evaluating in situ recovery (ISR) uranium projects to assess amenability of sandstone ores to the process. 2) Uranium mineral compositions can vary within deposits and do not always have well-defined elemental makeups. Other mineral compositions also impact leaching. 3) Characterization of multiple drill cores is necessary since mineralogical and leaching characteristics can differ within and between deposits. 4) Leaching tests on examples showed recoveries met targets of over 80% and optimizations improved recoveries up to 10% per ore, not dependent on grade. Elements of concern showed variable leachability based on host minerals.

1. Milling Underground - The Importance of
Mineralogy and Leach Studies in the Evaluation
of In Situ Recovery Projects
G.W. Heinrich, R.J. De Klerk, L. Reimann, E. Lam and C. Foldenauer
Cameco Corporation
IAEA Technical Meeting on the
Origin of Sandstone Uranium Deposits - A Global Perspective
May-June 2012, Vienna

2. Forward-looking Statement
Please note that the statements made in this presentation,
including statements regarding the company’s objectives,
projections, outlook, estimates, expectations or predictions, are
considered to be forward-looking information and statements
under Canadian and US securities laws. This information
involves risk and uncertainty and actual results could differ
materially. In addition, material factors or assumptions were
applied in drawing the conclusions contained in them.
Additional information about the material factors that could
cause the results to differ materially, and the material factors or
assumptions that were applied, are contained in Cameco’s
current Annual Information Form and MD&A, which are
available on SEDAR and EDGAR.
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3. Introduction
● What is in situ recovery (ISR)?
- Schematic of typical alkaline ISR operation
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4. Introduction
Operational requirements, characteristics and
performance for ISR (for typical sandstone ores):
1. Impermeable layers above and below ore horizon
2. Water-bearing open pore space (typically 15-30%)
3. Sufficient permeability (normally 0.7 to 1 d)
4. Leachable uranium minerals (typical uranium leaching
recovery target = 80%)
5. Uranium mineralization accessible to leach solutions
(allowing completion of leaching after 2 to 4 years or 50 to
200 pore volume replacements)
6. Sufficiently low contents of preg-robbing components (e.g.,
carbonaceous material)
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5. Introduction
Post-discovery technical evaluation of sandstone
orebodies for ISR:
● Delineation drilling
● Borehole geophysics/radiometry
● Borehole lithology/stratigraphy
● Hydro-geology
● Mineralogical and geochemical drill core characterization
● Metallurgical drill core characterization (leaching amenability
tests
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6. Core Evaluation Methods Used
Sample preparation (under an
inert atmosphere):
● Core splitting
● Intact texture sampling plus
polished section prep.
● Homogenization of half cores
● Test charge preparation
● Head sample cutting
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7. Core Evaluation Methods Used
Mineralogical characterization:
Head sample:
● Moisture determination
● Whole-rock analysis for main
element contents
● Uranium and impurity
analyses (e.g., vanadium and
selenium)
● X-ray diffractometry and
Rietveld analysis for main
mineral contents X-ray powder diffractometer
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8. Core Evaluation Methods Used
Mineralogical characterization:
Samples with intact texture:
● Porosity and pore size
determination
● Reflected light microscopy for
quality of polish and for
carbonaceous matter
● Scanning electron
microscope/microprobe
analyses for uranium
minerals, trace minerals and
ore texture (e.g. for
determination of uranium
mineral accessibility to
solutions)
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9. Core Evaluation Methods Used
Metallurgical characterization:
Pressurized bottle roll tests (under oxygen pressure) to
determine leaching chemistry (example of six parallel tests
shown)
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10. Core Evaluation Methods Used
Metallurgical characterization:
Pressurized column leach tests
(under oxygen pressure) for
leaching and ion exchange tests
(Example of two parallel tests
shown)
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11. Ore Mineralogy
Example of poresizer application (deposit 1):
Correlation of calculated montmorillonite content (based on
magnesium assay) with pore surface area
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12. Ore Mineralogy
Example of ore compositional data (deposit 1):
Area in Mineral XRD/Rietveld
F
Micrograph Content (%)
A Quartz 56.2
E B Albite 8.9
C K-feldspar 12.1
D Micas: Muscovite/Illite 1.9
A
D E Pyrite/Marcasite 0
F Kaolinite 5.5
Montmorillonite * 15.4
Total: 100
* by Mg assay obtained with
Cu K-alpha
B wavelength
A C
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13. Ore Mineralogy
Examples of uranium mineralization solution accessibility
A
A
B
Solution accessible uranium
mineralization with a composition of
calcium-phosphorus-bearing coffinite and Poorly solution accessible uranium
uranium-bearing clay, associated with mineralization (A) with shapes of
clay, pyrite and zircon in deposit 1 core framboidal pyrite in a clay matrix (B)
in deposit 2 core
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14. Ore Mineralogy
Uranium mineralization texture and genesis
Micrograph of uranium mineralization with Micrograph of uranium mineralization
euxenite and clay in a corrosion pocket in with a composition of calcium-
chlorite in deposit 1 core phosphorus-bearing coffinite around
corroded framboidal pyrite in deposit 1
core
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15. Ore Mineralogy
Uranium mineralization texture and genesis
Ca-P-coffinite apparently displacing
illite that had formed from K-feldspar.
Rounded oxygen deficient particles in
upper part of the image with contents
of uranium, iron, sulphur and silicon
show shapes typical for micro-
organisms (deposit 3 core)
Energy dispersive microanalysis:
Spectrum O Mg Al Si P S Cl K Ca V Fe As U Interpretation
A 24.3 0.5 5.9 1.6 0.4 1.8 0.3 0.8 64.4 Ca-P-coffinite
B 56.9 43.1 Quartz
C 50.3 49.7 Quartz
D 47.1 0.2 8.5 28.4 10.6 1.0 4.2 K-feldspar, U-min
E 21.0 0.8 6.1 1.8 0.5 0.3 1.9 0.4 1.7 65.5 Ca-P-coffinite
F 7.1 0.6 43.5 0.3 41.9 1.0 5.7 Pyrite, U-min.
G 7.1 3.8 1.4 12.0 0.3 1.6 0.4 13.7 59.8 Org., U-min., pyrite
H 12.7 5.2 2.2 1.7 0.6 2.1 0.4 2.5 72.7 Ca-P-coffinite, org.

16. Ore Mineralogy
Overall mineralogy summary and comparison
Estimated Content
Mineral
Deposit 1 Deposit 2
Core 1 Core 2 Core 1 Core 2
Quartz 56.2 50 62 71.1
Orthoclase 12.1 17.8 7 2
Albite 8.9 9.4 10.3 0
Muscovite/illite 1.9 7.7 2.1 4.1
Kaolinite 5.5 11.5 6.7 4
Montmorillonite * 15.4 3.7 11.1 18.4
Total Clays 22.8 22.9 19.9 26.5
Pyrite ** 0.8 0.4 0.9 0.4
* Not amenable to Rietveld analysis - estimated by EDX analyses for magnesium
** Estimated by EDX analysis for sulphur
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17. Ore Mineralogy
Uranium mineralogy summary and comparison
*
Estimated Content
Uranium Mineral Deposit 1 Deposit 2
Composition Type
Core 1 Core 2 Core 1 Core 2
Ca-P bearing coffinite 35% 85% 83% 62%
Uraninite/pitchblende 39% 8% 17% 8%
Coffinite 27% 8% 0% 0%
Autunite 0% 0% 0% 31%
Solution accessibility good good good good
Uranium head grade 2,200-2,600 2,000- 700 1,000
(ppm) 2,100
* Based on approx. 20 observations per core
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18. Ore Mineralogy
Influence of uranium minerals on leaching requirements
Uranium minerals requiring
oxidants
Name Valency
Uraninite U4+
Pitchblende U4+
Thucholite U4+
Coffinite U4+
Uranothorite U4+
Brannerite U4+
Davidite U4+
Pyrochlore U4+
Euxenite U4+
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19. ISR Leaching Simulation
Summary and comparison of optimized bottle roll leach test
results
Uranium Recovery
Leaching Time (%)
(h)
Deposit 1 Deposit 2
Core 1 Core 2 Core 1 Core 2
86 41 46.5 71.1 77.4
598 81-91 -- -- --
672 -- 79.2 -- --
720 -- -- 83 87.1
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20. ISR Leaching Simulation
Column leach tests – example of absolute uranium recovery
kinetics
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21. ISR Leaching Simulation
Column leach tests – example of leach solution volume-based
uranium recovery kinetics
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22. ISR Leaching Simulation
Estimate of possible ISR improvements from alkaline lixiviant
optimization
Ore Sample Standard Optimized Uranium
Origin Uranium Uranium Recovery
Recovery Recovery Improvement
** **
(%) (%) (%)
Deposit 1 65 72 7
Deposit 2 80 85 5
Deposit 3 70 80 10
Deposit 4 83 88 5
Average * 6.4
* resource size weighted
** by optimizing leach chemistry - bottle roll tests
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23. Impurities
Modes of occurrence of arsenic and selenium (elements of
concern)
Backscattered electron micrograph of Backscattered micrograph of ferroselite
zoned pyrite in roll-front ore (0-2% As, (FeSe2) in marcasite and/or pyrite in roll-
present in outer zones, deposit 1, front ore (deposit 1, core 3)
core 3)
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24. Impurities
Occurrence of vanadium (an element of concern) with uranium
mineralization
Backscattered electron
micrograph and elemental
composition of uranium-coal
mineralization consisting of a
coffinite-tyuyamunite type
mixed composition with
associated minerals (in
deposit 3, core 1)
Microanalyses by EDX (%)
Spectrum C O Na Al Si P Cl Ca V Fe U Total Interpretation
6A 23.5 0.6 0.3 7.6 0.6 2.7 3.0 0.6 61.1 100.0 coffinite-tyuyamunite?
6B 22.5 0.4 0.2 7.6 0.8 2.5 2.6 63.6 100.0 coffinite-tyuyamunite?
6C 25.9 0.6 0.1 7.5 0.7 2.8 3.0 59.5 100.0 coffinite-tyuyamunite?
6D 78.6 20.7 0.7 100.0 carbonaceous material
6E 79.1 20.2 0.7 100.0 carbonaceous material
6F 52.6 47.4 100.0 quartz
6G 51.4 48.6 100.0 quartz
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25. Impurities
Comparison of impurity grades and recoveries to leach solution
in bottle roll leach tests
Parameter Units Sample Origin
Deposit 1 Deposit 3
Ore Grade
As (ppm) 27 4
Se (ppm) 14 160
V (ppm) 39 80
Recovery to Solution
As (%) 0.4 3.3
Se (%) 14.8 0.2
V (%) 0.1 16
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26. Summary & Conclusions
● Mineralogical studies and laboratory bottle roll and column
leaching tests are well established methods to assess the
amenability of sandstone ores to ISR.
● Uranium minerals can vary considerably within a given
deposit and do not always give well-defined elemental
compositions - as was the case with a compound interpreted
as calcium-phosphorus-bearing coffinite.
● The mineralogical characteristics and final uranium leaching
recoveries can vary equally within and between individual
deposits, thus necessitating characterization of drill cores
from multiple locations within an ISR deposit.
● In the examples given, the final uranium recoveries of
optimized tests were not dependent on ore grades and met
the target of >80% in most cases - showing improvements of
up to 10% per ore.
● Elements of concern displayed variable leachability that
depended on the characteristics of their host minerals.
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27. Acknowledgements
The authors are indebted to:
● The members of the Cameco Technology and Innovation-
Research Centre (CTI-RC) hydrometallurgy team for sample
preparation and for carrying out the leaching tests
● The members of the CTI-RC Mineral and Chemical Analysis
Laboratory team for sample characterization and analyses
● Simon Reid for review of this presentation
● Cameco management for sponsoring the related projects and
for permission for this presentation
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28. Questions?
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