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Innovation with Integrity

Rare Earth Element Prospecting and Production,Starring Analytical X-ray as Indiana Jones!

Bruker AXSMadison, WI

Today’s Topics

• Introduction to the Rare Earth Elements

• What, where, and other important facts

• Economics and uses

• Deposits, resources and production

• Analytical Tools

• Mineralogical Analysis

• Chemical Analysis

Welcome

20.05.2011 2

Speakers

Alexander SeyfarthProduct Manager, XRFMadison, WI USA

Holger CordesApplications Scientist, XRDMadison, WI USA

Introduction to Rare Earth ElementsWhat are they?

Rare Earth Elements (REE) are a group of chemical elements that occur together in the periodic table: 15 Lanthanide elements + Sc and Y

REE are soft, malleable, ductile and usually quite reactive metals.

MP range from 798 to 1663 deg C(CORDIER & HEDRICK, 2010)

All REE are classified as metals. Chemical properties are similar and often all of them occur together in the same minerals.

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Use of Individual Rare Earth Elements

Usage of rare earth minerals by gigagrams (Gg). Credit: Xiaoyue Du and T. E. Graedel

InnovationNewsDaily Senior Writer Jeremy Hsu on Twitter @ScienceHsu

• Importance and use of REE grows with increased use of ―battery‖ and ―Clean Air‖ related technology

Clean Air and Hybrid Car TechnologyRequire REE

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• Applications lack substitutes

• Linked to global supply chain

National Security is Impacted by REE

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World REE Mineral Reserves and Production

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U.S. Geological Survey, Mineral Commodity Summaries, January 2011

• In 2010, China announced it would significantly restrict REE exports to ensure supply for Chinese domestic manufacturing

• 72% REE export reduction in 2010

• 35% REE export reduction in 2011

• Quota reduction officially to curb ―rampant and unregulated‖ production over the last few years, which has caused significant environmental problems

Chinese Era of REE Domination

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• The New York Times reported that the Chinese Central Government is placing all ―provincial‖ districts under oversight, removing local officials and taking steps towards a ―National Rare Earth Mining Area‖

• US Government is pressuring China for assurance on exports; China is leery of international commitments

• Most Chinese deposits are unique with very high concentrations of heavy REE, such as Sm and Dy, and lowest contamination of Th

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Chinese Mining Under Government Control

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Demand and Production

Are Rare Earth Elements Rare?

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Where Can We Find REE?

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• REE are relatively abundant in the earth’s crust, but discovered mineable concentrations are less common than other ores

• Main minerals within the ore resources are bastnaesite and monazite

• Mineralizations are associated with:

• Carbonatite complexes

• Bauxite/laterites

• Absorbed in clays (IAClays)

• Magnetite

• Uranium deposits

• Vein (hydrothermal)

• Placer (residual)

• Peralkaline Igneous deposits

REE Ores and Minerals Are Very Complex

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• What tools are there for the characterization of minerals and ores?

The Instrument-Makers’ Solutions

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• Traditional mineralogical analysis is done by microscopy or phase separation

• Shape, color, symmetry, refractive index, etc.

• For complex rocks, an electron microprobe is used, combining imaging with elemental analysis

• There is a direct way to identify minerals as well!

Mineralogical Analysis

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Mineral Identification by XRD

50484644424038363432302826242220181614

Bastnaesite

Monazite

Image: www.mindat.org\ min-2751.html

Image from www.wikipedia.org

Unit cells Powder diffraction patterns

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What Kind of Information Can Be Obtained From a Powder Diffraction Pattern?

• Peak position dimension of the unit cell, lattice parameters, space group

• Peak intensity content of the unit cell, atomic positions

• Peak broadening strain/crystallite size

• Scaling factor weight percent of phase

• Background degree of crystallinity

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Powder Diffraction BasicsSample

Diffraction of an ideal powder

Diffraction of a small number of crystallites ("spotiness effect")

Diffraction of textured materials

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Point detectors • Scintillation

detector• XFlash® detector

PSD• VÅNTEC-1• LYNXEYE

Area detectors• VÅNTEC-500• VÅNTEC-2000

Detector Options for Mineral Analysis

Commonly used for routine Rietveld analysis with Bragg-Brentano geometry

Can be used for Rietveld analysisof small spots,micro-diffraction, mapping, non-ideal powders

High speed analysis, quality control

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Bastnaesite Ore Measured in D2 PHASER

• D2 PHASER

• LYNXEYE detector with 5.6 opening and Ni filter

• 0.6 mm divergence slit

• 2.5 primary Soller, 4 secondary Soller

• 0.02 steps, 0.5 s/step

• 25 minutes

• XFlash® detector

• 2 mm divergence slit

• 0.2 mm receiving slit

• 2.5 primary Soller, 2.5 secondary Soller

• 0.02 steps, 10 s/step

• 8 hours, 30 min

2-Theta - Scale

15 20 30 40 50 60 70

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REE Concentrate Measured in D2 PHASERPhase Identification with EVA

• D2 PHASER

• LYNXEYE detector with 5.6 opening and Ni filter

• 0.6 mm divergence slit

• 2.5 primary Soller, 4 secondary Soller

• 0.02 steps, 0.5 s/step

• 25 minutes

00-005-0586 (*) - Calcite, syn - CaCO3

00-036-0426 (*) - Dolomite - CaMg(CO3)2

01-071-2393 (C) - Strontianite - SrCO3

00-046-1295 (I) - Monazite-(Ce) - (Ce,La,Nd)PO4

01-083-0077 (C) - Synchysite-(Ce) - CeCaF(CO3)2

00-038-0400 (I) - Hydroxylbastnasite-(Nd) - NdCO3(OH)

00-011-0340 (I) - Bastnasite-(Ce) - CeCO3F

File: sample 180071 0.6mm lynxeye 5.6dg 4dg soller_disc0.19.raw

2-Theta - Scale

10 20 30 40 50 60 70 80 90

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Phase Identification Using DIFFRAC.EVA Software and Elements as Filter Criteria

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Phase Identification Using DIFFRAC.EVA Software

Counts

10 20 30 40 50 60 70

2Theta (Coupled TwoTheta/Theta) WL=1.54060

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

20.05.2011 23

Element Identification Using D2 PHASER with XFlash® Detector, Bastnaesite Deposit

• Collected at 45incident angle for

10 minutes

• Ce and Nd can be identified, possibly Pr and very minor Y

20.05.2011 24

Element Identification Using D2 PHASER with XFlash® Detector, Concentrate

• Collected at 45incident angle for

10 minutes

• La, Ce, Pr, Nd, Smcan be distinguished

20.05.2011 25

Quantitative Mineral Analysis Using X-ray Diffraction

Standard-based methods

• Conventional method (DQuant): Calibration curve with standards required, mostly used for quality control, accurate but problematic with peak overlap between phases

• Reference intensity ratio method: Quick semi-quantitative method for many minerals using the I/Icor values from the ICDD database (can be done in EVA program)

• Full pattern analysis: Scaling of full patterns of standard minerals, very consistent sample preparation and standard minerals necessary

Standardless methods

• Rietveld analysis with TOPAS: standard-less, peak overlap between phases can be resolved, all crystal structures have to be known

20.05.2011 26

The Rietveld Method

• Standardless full-profile approach to quantitative phase analysis• Uses every data point as a unique observation and least-squares methods to

minimize the difference between calculated and measured intensities• Residual of Least Square Refinement

R = Σ wi(yi – yci)2

Rietveld Analysis requires: • The crystal structure data for every phase in a mixture (unit cell and atomic

positions) • A model for the peak shapes and widths and a model for any aberrations• A model for the background

The relative masses of all phases contributing to the diffraction pattern can be derivedfrom the refinement using the simple relationship:

Wr = Sr (ZMV)r / t St (ZMV)t

Wr is the relative weight fraction of phase r in a mixture of t phasesS is the scale factor derived from Rietveld refinementZ is the number of formula units per unit cellM is the mass of the formula unit (atomic mass units)V is the volume of the unit cell (Å3 ).

20.05.2011 27

Bastnaesite Deposit Quantitative Analysis Using TOPAS Software

20.05.2011 28

Bastnaesite DepositQuantitative Analysis Using TOPAS Software

20.05.2011 29

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ConcentrateQuantitative Analysis Using TOPAS Software

20.05.2011 35

Solid Solution EffectsSchematical Representation

20.05.2011 36

Solution PhasesQuantitative Analysis Using TOPAS Software

20.05.2011 37

• Absolute method for direct and highly accurate quantitative phase analysis of mineral mixtures, if the crystal structures are known

• Standardless method for determination of phase amounts, lattice parameters, crystallite size and much more

• Independent of equipment and sample properties such as tube aging, solid solution effects, and preferred orientation

• Intrinsic handling of solid solution and preferred orientation effects

• Operator-independent

• Can be operated without human interaction (TOPAS BBQ)

Quantitative Rietveld AnalysisAbsolute and Standardless

20.05.2011 38

• R & D, Centralized Lab

• Most flexible unit, capable of all shown applications

• Widest range of components

• Highest power/flux and smallest spot sizes

• Process Analysis

• Quantification with large, sturdy sample changer

• Ease of use

• High power

• Tie into automated concepts

InstrumentationLaboratory or Process Instrumentation

20.05.2011 39

• Fastest desktop X-ray diffractometer

Choice of

• LYNXEYE detector

• Scintillation counter

• XFlash® detector

• Completely self-contained, including cooling and PC

• Rugged instrument with high resolution for complex minerals

• Highest resolution XRD/XRF unit

Benchtop Diffractometer

20.05.2011 40

In Addition to Minerals, We Need to Know the Chemistry!

20.05.2011 41

• Classical ―wet‖ chemical approach

• Atomic Spectroscopy approaches:

• Beers Law (absorption proportional to concentration)

• Free atoms (outer electron shell interactions)

• Detection with a variety of detectors

• Different techniques

• AAS

• ICP

• ICP MS

• LIBS

• LA-ICP-MS

• X-ray Spectroscopy

Elemental Analysis for REE

NEW ICP-MS M90

20.05.2011 42

XRF is the method for:

• doing qualitative and quantitative analysis of elemental composition

• by excitation of atoms and detection of their characteristic X-rays

XRF: X-ray Fluorescence Analysisor X-ray Spectrometry

20.05.2011 43

XRF Sample Preparation Approaches

20.05.2011 44

How Characteristic X-rays are Generated in an Atom

20.05.2011

X-ray Energy Distribution from an X-ray Tube (Rh)

mA setting

controls

number of

photons

kV setting

determines

excitation

energy

20.05.2011

Bond energy of the electron

Absorption edge/ Excitation Potential

Excitation / Emission of Characteristic X-ray Radiation

Energy of incoming photon

20.05.2011 47

X-ray Emission Energies

20.05.2011 48

• Excitation Voltage: Rule of thumb is minimum 3x higher than emission line energy

• Detection of characteristic lines requires adequate resolution of the instrument

• The higher the emission energy the larger/thicker the analyzed layer of sample

• Calibration based on matrix matched reference material or by means of FP (makes possibly semi quantitative)

Exciting Rare Earth Elements… Using X-rays

20.05.2011 49

XRF: X-ray Fluorescence Analysis

Energy of X-ray photons• Which element

• Qualitative analysis

Number of X-ray photons at a given energy • What concentration

• Quantitative analysis

Sample

20.05.2011 50

Energy-Dispersive XRF

20.05.2011 51

Wavelength-Dispersive XRFSequential

20.05.2011 52

Wavelength-Dispersive XRFSimultaneous, Multielement Channel™

20.05.2011 53

EDXRF versus WDXRF

20.05.2011 54

XRFSelecting the Right Tool for the Job

• What equipment can be used where?

• What can we determine?

• Which tool to use for the job?

20.05.2011 55

REE Exploration

Search for deposits

Qualification of deposits

“accelerating” discovery

20.05.2011 56

• Usually, all REE are present, with various ratios in high concentrations

• Light REE vs. Heavy REE are of economic interest

• Y, Sc is indicator for HREE presence

• Detecting Y, Ce, La is critical for REE exploration

• Detecting Th is important as well since it ―penalizes‖ the value due to increased processing:

• Th concentration is low!

• Most ores are very high in Fe, Ca and also contain Sr and Nb(more interferences on EDX)

• Matrix affects quantification, and reference samples should be used for calibration which potentially matches the unknowns:

• Chicken or Egg Question?

• Data needs to be related to 3-D space / map

Exploration: Analytical Challenge

20.05.2011 57

Excitation in Practice

• EDXRF units: 50 kV max. (HH units around 45 kV)Resolution < 150 eV at >100,000 total cps with XFlash® detector

• Power level from 1 Watt (HH) to 50 Watt (Benchtop)

• K-Lines for Ce, Pr, Nd can be detected and easily separated, but yield is low

20.05.2011 58

• Using best-in-class resolution (<145 eV at 100,000 cps), L-lines cannot be easily separated

EDXRF Detection of REE L-Lines

20.05.2011 59

Ce, Pr, Nd Detection on 45-kV EDXRF (1.2 Watt)

15 20 25 30 35

- keV -

Pulses

Ce Ce Ca Gd Gd La La

Y Y Pr Pr

Fe Yb Yb Tm Tm

Pb Pb Nd

Sn Sn Rh

15 20 25 30 35 40

- keV -

Pulses

Ce Ce Ca Gd Gd La La

Y Y Pr

Fe Yb Yb

Pb Pb Nd

Y K1 Sum

Y KB Sum

LOG Scale

For best yield, we need

higher power…

20.05.2011 60

K-Lines Using 60-kV WDXRFBastnaesite Ore

Pressed 1 60 KV None XS-400 0.23 degr.

Pressed 1 60 KV None LiF200 0.23 degr.

28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

20.05.2011 61

Gadolinite Mineral on Handheld Unit

5 6 7 8

- keV -

x 1E3 Pulses

Ce Ce Ce Ca Ca Gd Gd Gd La La La

Rh Rh Rh Y Y Y Pr Pr Pr Sr Sr Sr

Yb Yb Yb Tm Tm Tm

Er Er Er Ho Ho Ho Dy Dy Dy

Pb Pb Pb Nd Nd Nd Sm Sm Sm Eu Eu Eu

5 10 15 20 25 30

- keV -

Pulses

Ce Ce Ce Ca Ca

Gd Gd Gd La La

Rh Rh Rh Y Y Y

Pr Pr Pr

Er Er Er

Pb Pb Pb

20.05.2011 62

WDXRF L-Line Separation0

4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7

20.05.2011 63

WDXRF L-Line Separation 0

4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7 7.1

20.05.2011 64

Particle Size Effects of HeterogeneousPowder Samples

Compound Line Concentration

Energy

Thickness [m]

Fe2O3 Fe KA1 0.722 6.40 174

MnO Mn KA1 0.016 5.89 139

TiO2 Ti KA1 0.016 4.51 66

CaO Ca KA1 30.12 3.69 104

K2O K KA1 0.103 3.31 77

SO3 S KA1 0.000 2.31 27

P2O5 P KA1 0.004 2.01 19

SiO2 Si KA1 1.130 1.74 13

Al2O3 Al KA1 0.277 1.49 8

MgO Mg KA1 21.03 1.25 7

Na2O Na KA1 0.029 1.04 4

CO2 46.37

Thickness of the

sample from which

90% of the

measured intensity

is derived

NBS 88b dolomite

Pressed pellet

without binder

Especially for the lines of light elements,

average grain size layer thickness

(typically grain sizes vary between : 20 - 200 m)

20.05.2011 65

• Direct measurements on rock face are limited by the analyzed layer of the sample (physics) and is independent of instrumentation

• Homogeneity is important: analysis of powders is best done on a portable stand setup!

• Factory calibration with type standardization for custom materials using one or two samples will have only limited accuracy

• Using generic ―non-calibrated‖ approach and using element ratios enables universal mapping of relative abundance

• Ideally, a custom calibration of major formations is done using characterized reference material for best accuracy!

Prospection for REE with Geochemical Exploration Tools:Recommendations for Portable or HH-XRF

20.05.2011 66

Prospection for REE with Geochemical Exploration Tools:Recommendations for Portable or HH-XRF

• 45 kV or higher excitation

• Resolution of detector <145 eV also at high count rates

• Higher power (BT) unit for Th and more K signal

Direct mapping data from the field can be averaged and reprocessed in camp

Loose powder or pellet approach yields better data than rock face

FP-based calibrations

Matrix matched calibrations for best performance

Customized calibration approaches

20.05.2011 67

Mining

20.05.2011 68

• High variable matrix for some locations

• All REE need to be quantified

• Th, U and other elements as well

• High precision

• Easy to use in ―challenging location‖

• Cost effective – less consumables

Mining Samples Analytical Challenge

20.05.2011 69

The Solution Lies in the Sample Preparation

20.05.2011 70

www.bruker-axs.com/webinars_xrf

MiningRecommendation for XRF

Where to mine and what?

HH-XRF or pXRF for grade control in the pit/mine

WDXRF for blast-hole screening

Mined ore can be

• Product

Accurate analysis for value

• Feed to processing plant

Variable ore requires sturdy calibration

model with screening for all elements

Various methods need to be applied,

elemental flexibility from F to Am!

WDXRF is most-suited tool

20.05.2011 71

Processing and Recovery

20.05.2011 72

The ability to process is very, very critical and very, very complex”Mark Smith of Molycorp

’5th International Rare Earths Conference’ Hong Kong, 2009

• Producing rare earth oxides is considerably harder than other mining processes

• Rare-earth element extraction involves many steps. In the case of bastnaesite, usually found in igneous rock formations, the ore is mined using traditional open-pit techniques. The bastnaesite is then removed from the rock by crushing the ore into a small gravel, and then grinding the crushed ore in a mill until it becomes a fine sand. That sand, or silt, gradually separates into different mineral grains — bastnaesite and other generally less valuable minerals. The silt is then run through a floatation process wherein a liquid element is added, and air bubbles introduced. The finer bastnaesite silt sticks to the bubbles and rises to the top of the liquid where it is skimmed off.i

• That is the first process. The bastnaesite must now be separated into its constituent rare earth elements. The mineral is usually sent to a separation plant where each element is separated using an acid or solvent extraction process.

“It’s a very long and involved process. That’s one of the biggest risks.It can take dozens, hundreds of steps to separate the rare earths.”

Yaron Vorona, Executive Director Institute for the Analysis of Global Security’s Technology and Rare Earth Metals Center

The Washington Independent, October 25, 2010

Mining is Easy… Processing is Not…

20.05.2011 73

• Instrument needs to be protected against spills, operator mistakes

• Direct, easy access to measurement position

• Protection over tube and secondary side

• Flexible setup requires that solid samples and liquid samples are processed on same system

• Fast change-over

• Fail-safe operation

• Helium purge needs to be at atmospheric pressure

• Sample needs to stay cool

Processing of the Ore UsingOrganics and Acids

20.05.2011 74

• Widest dynamic range: % to PPM

• Best resolution (High conc. next to low conc.)

• Better than 0.1% relative for concentrates and minors

• Configuration tunable for desired element combinations

• Solid and liquid samples can be analyzed directly

• Calibrations built once, then operational for years!

• QA/QC done by stable monitor samples

• Can be operated by… operators

• ―Retools‖ to different applications

• Universal Calibration Mode enables measurement and quantification of complete unknowns (e.g. process issue samples)

• Cost of operation/consumables much lower than atomic spectroscopy!

Process Control / Beneficiation of REEWDXRF Advantages

20.05.2011 75

• X–ray techniques are ideal complements for both field- and lab-based prospecting campaigns:

• Elemental quantification

• Mineral identification and quantification

• Mining and processing

• X-ray techniques are ideal to:

• Quantify: lower operating cost than ICP/AAS and less consumables

• One calibration is stable for years!

• Optimizing the processing chemistry for the mineralization

• XRD is used in the Cu mining industry as primary tool for leaching

SummaryREE Prospecting & Production

20.05.2011 76

Any Questions?

Please type any questions

you may have for our speakers

in the Q&A panel and

click Send.

20.05.2011 77

For more information:

Check out Bruker Training Central (BTC) online training courses on www.brukersupport.com

• XRF Basics I: From Theory to Intensity (two 1-hr videos)

• XRF Basics II: From Intensities to Concentrations (two 1-hr videos)

• XRF Sample Preparation (two 1-hr videos)

• Fundamentals of Powder XRD (two 1-hr videos)

• Powder XRD Data Collection and Analysis (two 1-hr videos)

• Basics of Two-Dimensional XRD (two 1-hr videos)

Register for our upcoming webinar:

• XRF and Microanalysis in Geoscience, Jun 21, 2011

Visit us at:

• Denver X-ray Conference, Colorado Springs, CO, Aug 1-5, 2011

• Geological Society of America, Minneapolis, MN, Oct 9-12, 2011

20.05.2011 78

Thank you for your attention!

Innovation with Integrity

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