Crystal Chemistry and Structure of Anomalous Birefringent Cubic Uvarovite Garnet, Ideally Ca3cr2si3o12

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2017 Crystal Chemistry and Structure of Anomalous Birefringent Cubic Uvarovite Garnet, Ideally Ca3Cr2Si3O12

Salvador, Jeffrey

Salvador, J. (2017). Crystal Chemistry and Structure of Anomalous Birefringent Cubic Uvarovite Garnet, Ideally Ca3Cr2Si3O12 (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/25496 http://hdl.handle.net/11023/3906 master thesis

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Crystal Chemistry and Structure of Anomalous Birefringent Cubic Uvarovite Garnet, Ideally

Ca3Cr2Si3O12

Jeffrey Juan Salvador

A THESIS

SUBMITTED TO THE FACULTY OF GRADUATE STUDIES

IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE

DEGREE OF MASTER OF SCIENCE

GRADUATE PROGRAM IN GEOLOGY AND GEOPHYSICS

CALGARY, ALBERTA

June, 2017

Anomalous birefringent uvarovite (Uv) garnets from the Ural Mountains, Russia (SAR-1,

SAR-2, and SKR-1), Zermatt, Switzerland (STZ-1), Jacksonville, Tuolumne County, California

(JTC-1), and Outokumpu, Finland (FIN-1) were analyzed using synchrotron high-resolution powder X-ray diffraction (HRPXRD) and electron microprobe analysis (EMPA) in order to understand the crystal chemistry and structure that causes the occurrence of optical anisotropy.

HRPXRD detected the existence of fine scale intergrowths of two (SAR-2, STZ-1, and JTC-1), three (SAR-1), and up to four (FIN-1) additional cubic phases of Uv, with slight changes in the a unit-cell parameter representative of distinct chemical compositional phases obtained by EMP analyses. The a unit-cell parameter ranges from 11.91425(2) Å in SAR-1b to 12.05305(2) Å in

JTC-4a and based on the garnet end-member composition, uvarovite ranges from Uv9Adr88Grs2 in JTC-4a to Uv71Grs24Sps1 in FIN-6a. Rietveld refinement X-ray diffraction traces show no deviation from cubic symmetry and reveal consistent peak profiles with the appearance of broadening and asymmetrical peak effects caused by the existence of additional microscopic cubic uvarovite phases intergrown together. These multiphase intergrowths contain strain derived from lattice mismatch of slightly different a unit-cell parameters against boundary contacts between phases and ultimately give rise to the observed birefringence in uvarovite, and possibly to other garnet end-member species.

ii ACKNOWLEDGEMENTS

I would first like to express my deepest gratitude to my supervisor, Dr. Sytle M. Antao for her continuous guidance; advice, financial support, and feedback as well as her encouragement to optimize my potential by giving me more responsibility throughout the course of my degree. I would also like to thank Dr. Robert Marr for his assistance with the Electron

Microprobe Analysis, including calibration, sample mounting, and instructions on using the electron microprobe.

This project was funded in part by an NSERC Discovery Grant. Synchrotron HRPXRD data was collected by Dr. Antao at beamline 11-BM, Advanced Photon Source (APS), Argonne

National Laboratory (ANL). I would also like to extend my appreciation to my mineralogy research group members: Nes, Laura, Lynsey, and Inayat for their advice, encouragement, and insightful discussions throughout my time at the University of Calgary.

Thank you to my friend, Michelle Bjorndalen for reviewing my thesis and providing helpful feedback. Lastly, I would like to thank my family and friends for their continued love, support, and motivational conversations throughout my degree.

iii TABLE OF CONTENTS

ABSTRACT ...... ii ACKNOWLEDGEMENTS ...... iii TABLE OF CONTENTS ...... iv LIST OF TABLES ...... vi LIST OF FIGURES ...... viii

CHAPTER 1: INTRODUCTION ...... 1 1.1 Purpose ...... 1 1.2 Organization of this Thesis ...... 2 1.3 Garnet ...... 3 1.4 Uvarovite Garnet ...... 5 1.5 Crystal Chemistry of Uvarovite Garnet ...... 7 1.6 Crystal Structure of Uvarovite Garnet ...... 8 1.6.1 Dodecahedral {X} Site ...... 10 1.6.2 Octahedral [Y] Site ...... 12 1.6.3 Tetrahedral (Z) Site ...... 13 1.7 Previous Research on Anomalous Birefringent Garnets ...... 14 1.7.1 Twinning ...... 15 1.7.2 Cation Ordering ...... 15 1.7.3 Hydrous Components ...... 17 1.7.4 Compositional Heterogeneity ...... 19 1.7.5 Additional Cubic Phase Intergrowths ...... 20

CHAPTER 2: EXPERIMENTAL TECHNIQUES ...... 22 2.1 Sample Description ...... 22 2.1.1 SAR-1, SAR-2, and SKR-1 ...... 22 2.1.2 FIN-1, JTC-1, and STZ-1 ...... 24 2.2 Optical Microscopy ...... 24 2.3 Electron Microprobe Analysis (EMPA) ...... 27

iv 2.4 Synchrotron High-Resolution Powder X-Ray Diffraction (HRPXRD) ...... 28 2.4.1 Rietveld Structure Refinement ...... 29

CHAPTER 3: RESULTS AND DISCUSSION ...... 31 3.1 Electron Microprobe Analysis (EMPA) Results ...... 31 3.1.1 SAR-1 ...... 34 3.1.2 SAR-2 ...... 39 3.1.3 SKR-1 ...... 43 3.1.4 STZ-1 ...... 47 3.1.5 JTC-1 ...... 52 3.1.6 FIN-1 ...... 57 3.1.7 Comparison between the six uvarovites garnets ...... 62 3.1.8 Comparison with Literature ...... 66 3.2 Synchrotron High Resolution Powder X-Ray Diffraction (HRPXRD) Results ...... 74 3.2.1 Sarany, Urals, Russia (SAR-1) ...... 75 3.2.2 Sarany, Urals, Russia (SAR-2) ...... 80 3.2.3 Zermatt, Switzerland (STZ-1) ...... 83 3.2.4 Jacksonville, Tuolumne County, California, USA (JTC-1) ...... 88 3.2.5 Outokumpu, Finland (FIN-1) ...... 92 3.2.6 Unit-Cell Parameter Variations ...... 97 3.2.7 Site Occupancy Factors (sofs) and Chemical Composition ...... 100 3.2.8 Isotropic Displacement Parameters (U) ...... 103 3.2.9 Bond Distances ...... 104 3.3 Evaluation of Birefringence in Uvarovite Garnet ...... 111

CHAPTER 4: CONCLUSION ...... 116

REFERENCES ...... 118

APPENDIX A ...... 125

v LIST OF TABLES

Table 1.1. Ugrandite and pyralspite end member garnets ...... 5

Table 1.2. Structural symmetry, Wyckoff position, and coordination of Uv garnet (modified after Geller 1967) ...... 10

Table 3.1.0. Representative chemical and garnet end-member compositions for each phase of the six samples of ugrandite garnet ...... 33

Table 3.1.1. EMPA of three phases of Uv in SAR-1 and two phases in SAR-2 from Sarany, Urals, Russia ...... 38

Table 3.1.3. EMPA of three representative phases of uvarovite in SKR-1 from Saranovskii, Russia ...... 45

Table 3.1.4. EMPA of two phases of uvarovite in STZ-1 from Zermatt, Switzerland ...... 50

Table 3.1.5. EMPA of two different phases of uvarovite-andradite in JTC-1 from Jacksonville, Tuolumne County, California ...... 55

Table 3.1.6. EMPA of four distinct phases of Uv in FIN-1 from Outokumpu, Finland ...... 60

Table 3.2.1. HRPXRD data including Rietveld structure refinement statistics for uvarovite samples SAR-1 and SAR-2 ...... 78

Table 3.2.2. Atom coordinates, isotropic displacement parameters, U (x100) (Å2), sofs, and differences between phases for uvarovite samples from Russia: SAR-1 and SAR-2 ...... 79

Table 3.2.3. HRPXRD data including selected interatomic distances (Å) and Rietveld structure refinement statistics for uvarovite samples STZ-1 and JTC-1 ...... 86

Table 3.2.5. HRPXRD data including selected interatomic distances (Å) and Rietveld structure refinement statistics for uvarovite samples FIN-1 ...... 95

vi Table 3.2.6. Atom coordinates, isotropic displacement parameters, U (x100) (Å2), sofs, and differences between phases for uvarovite sample from Finland: FIN-1 ...... 96

Table 3.2.7. Uvarovite EMPA phase end-member relationships to corresponding HRPXRD single and multiple phases ...... 102

Table 3.2.8. Selected interatomic bond distances (Å) for five uvarovite garnet samples in this study ...... 110

Table 3.2.8. (Continuation) Selected interatomic bond distances (Å) for five uvarovite garnet samples in this study ...... 111

vii LIST OF FIGURES

Figure 1.1. Uvarovite on host rocks from a. Sarany Urals, Russia (SAR-1), d. Jacksonville, California (JTC-1), and g. Outokumpo, Finland (FIN-1). Photographs (2X) of SAR-1 in b. display two deep green shades with moss-like texture on host rock, JTC-1 in e. show diagnostic emerald green colour with light and dark green varieties, and FIN-1 in h. contain large dodecahedral opaque crystals up to 6 mm imbedded in matrix. Magnified Uv crystals (5X) in SAR-1 in c. show a homogenous emerald green colour with some exposed cubic faces, JTC-1 in f. show large euhedral crystals, and FIN-1 in i. display uniform deep green crystal fragments...... 6

Figure 1.2. Polyhedra representation of a garnet crystal structure with alternating dodecahedra (blue), octahedra (yellow), and tetrahedra (grey) projected down the a axis. Illustration shows a repeating pattern formed by the high number of shared edges outside the unit-cell (solid black square)...... 8

Figure 1.3. Garnet ball and stick model representing the tetrahedral oxygen coordination by {X} = Ca (blue), [Y] = Cr (yellow), and (Z) = Si (grey). Note the X-O bond length is longer than the X’-O bond, values are from Novak and Gibbs (1971)...... 9

Figure 1.4. Polyhedron model of the eight - coordinated triangular dodecahedron {X} site of garnet projected down an intermediate position between all three axes...... 10

Figure 1.5. Polyhedra models of dodecahedron edge sharing 10 of its 12 edges with a. four adjacent dodecahedra, b. four octahedra, and c. two tetrahedron...... 11

Figure 1.6. Polyhedra model of a six-coordinated [Y] site octahedron. The Y-O bond length value of uvarovite is from Novak and Gibbs (1971)...... 12

Figure 1.7. [Y] site octahedron edge sharing with six neighbouring dodecahedra...... 12

Figure 1.8. Polyhedral models of an a. (Z) Site tetrahedron and b. edge sharing with two adjacent dodecahedra. The Z-O bond length value of uvarovite is from Novak and Gibbs (1971)...... 13

Figure 2.1.1. Uvarovite crystals from a. Sarany Urals, Russia (SAR-2), b. Zermatt, Switzerland (STZ-1), and c. Saranovskii Mine, Russia (SKR-1). All crystals are up to 3 mm in size with minor quartz enclosing Uv crystals in SAR-2 and some exhibit a chromite core in SKR-1. STZ-1 displays a more complex Uv crystal of smaller broken fragments viewed under 10X magnification...... 23

Figure 2.2.1. SKR-1 viewed under 10X magnification in a. PPL image displaying deep green colour, an XPL view in b. displaying well defined extinction positions and in c. a fully illuminated ‘bowtie’ twinning structure is observed...... 25

viii Figure 2.2.2. JTC-1 displays faint green Uv garnet crystal fragments in PPL from a. to c. In d. to k. XPL images revealing optical anisotropic features of distinct zoning (f., h., and k.) with anomalous alternating extinction positions within a 360° stage rotation viewed under 10X magnification...... 26

Figure 3.1.1.1. a. BSE image of SAR-1 displaying subtle variations in contrast throughout the crystal fragment. Elemental maps of b. Al, c. Cr, and d. Mg. Distinct zoning is evident in the BSE, Al, and Cr images, while Mg shows no feature. EMPA obtained from the points labeled are given in Appendix A (Table A1.1). The scale bar in a. represents 100 µm...... 34

Figure 3.1.1.2. SAR-1 illustrating a. deep green colour in PPL with a dark chromite (Chr) core b. XPL image displaying distinct birefringence c. Reflected light image with prominent inclusions (Inc) and fractures and d. BSE image shows sharp variations in contrast with distinct zoning throughout the crystal. The scale bar in d. represents 200 µm...... 35

Figure 3.1.1.3. a. PPL image of SAR-1. b. XPL image displays optical anisotropy. c. Reflected light image highlighting the fractures and minor inclusions of chromite (Chr). d. BSE image show variations in contrast evident of zoning and traces of Chr. The scale bar in d. represents 200 µm...... 36

Figure 3.1.2.1. SAR-2 crystal A illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence c. Reflected light image with prominent oscillatory zoning and inclusions and d. BSE image shows EMPA points labeled are given in Appendix A (Table A1.2). The scale bar in d. represents 300 µm...... 39

Figure 3.1.2.2. SAR-2 displaying a. deep green colour in PPL b. XPL image displaying birefringent areas c. Reflected light image with prominent oscillatory zoning in the crystal and d. BSE image shows with EMPA points labeled are given in Appendix A (Table A1.2.). The scale bar in d. represents 500 µm...... 41

Figure 3.1.2.3. Apfu distribution from EMPA results for four analyzed points of SAR-2. a. {X} site show Ca2+ as the dominant cation. b. [Y] site partitioning shows a gradual increase in Cr3+ and decreasing Al3+. c. (Z) site displays Si4+ as the dominant cation...... 42

Figure 3.1.3.1. SKR-1 illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence with faint extinction positions c. Reflected light image with prominent inclusions in the crystal and d. BSE image with EMPA points labeled are given in Appendix A (Table A1.3). The scale bar in d. represents 500 µm...... 43

Figure 3.1.3.2. SKR-1 illustrating a. deep green colour in PPL b. XPL image displaying clear birefringence c. Reflected light image with minor inclusions in the crystal and d. BSE image shows with EMPA points labeled are given in Appendix A (Table A1.3.). The scale bar in d. represents 500 µm...... 44

Figure 3.1.3.3. Apfu distribution from EMPA results for seven analyzed points of SKR-1. a. {X} site show Ca2+ as the dominant cation. b. [Y] site partitioning illustrating a gradual increase in Cr3+ and decreasing Al3+. c. (Z) site contain Si4+ as the dominant cation...... 46

Figure 3.1.4.1. a. Reflected light image STZ-1 displays the EMPA analyses obtained from the points labeled are given in Appendix A (Table A1.4.). b. BSE image shows subtle variations in contrast throughout the crystal fragment. Elemental maps of c. Al, d. Cr, and e. Fe. Distinct variation in contrast is evident in the BSE, Al, and Cr images, while Fe shows no changes. The scale bar in b. represents 100 µm...... 48

Figure 3.1.4.2. STZ-1 displaying a. to d. deep green colour in PPL e. to h. XPL images show low birefringence i. to l. Reflected light image with inclusions and EMPA points labeled are given in Appendix A (Table A1.4). The scale bar in e. represents 500 µm...... 49

Figure 3.1.4.3. Apfu distribution from EMPA results for four analyzed points of STZ-1. a. {X} site partitioning with Ca2+ as the dominant cation. b. [Y] site partitioning displaying a gradual increase in Cr3+ and decreasing Al3+ and Fe3+. c. (Z) site partitioning displaying Si4+ as the dominant cation...... 51

Figure 3.1.5.1 a. BSE image of JTC-1 displaying distinct contrast in zoning boundaries. JTC-1 crystals b. and c. with EMPA points labeled are given in Appendix A (Table A1.5). The scale bar in a. and b. both represents 50 µm...... 52

Figure 3.1.5.2. BSE images of JTC-1 crystals from Jacksonville, California. a, b, c, d. EMPA points labeled 1 to 25 are given in Appendix A (Table A1.5). No distinct zoning or subtle contrasts were observed. The scale bar represents 100 µm...... 53

Figure 3.1.5.3. JTC-1 from Jacksonville, California illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence c. Reflected light image with minor inclusions and fractures and d. BSE image shows subtle variations in contrast. EMPA points labeled are given in Appendix A (Table A1.5). The scale bar in d. represents 100 µm...... 54

Figure 3.1.5.4. Apfu distribution from EMPA results for 25 analyzed points of JTC-1. a. {X} site partitioning with Ca2+ as the dominant cation. b. [Y] site displaying a gradual increase in Cr3+ and decreasing Fe3+. c. (Z) site show Si4+ as the dominant cation...... 56

Figure 3.1.6.1. FIN-1 from Finland illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence c. Reflected light image with prominent inclusions and fractures in the crystal and d. BSE image shows subtle variations in contrast with chalcopyrite and calcite inclusions. EMPA obtained from the points labeled are given in Appendix A (Table 1.6). The scale bar in d. represents 80 µm...... 58

Figure 3.1.6.2. FIN-1 illustrating a. Reflected light image with prominent inclusions and fractures in the crystal and d. BSE image shows subtle variations in contrast with chalcopyrite and calcite. EMPA analyses obtained from the points labeled are given Appendix A (Table 1.6). The scale bar in d. represents 100 µm...... 59

Figure 3.1.6.3. Apfu distribution from EMPA results for 15 analyzed points of FIN-1. a {X} site with Ca2+ as the dominant cation. b. [Y] site displaying a significant increase in Cr3+ from points 1 and 2 leading by a gradual increase in Cr3+ and inversely decreasing Al3+. c. (Z) site displaying Si4+ as the dominant cation...... 61 x Figure 3.1.7. Ugrandite ternary diagram between Uv, Grs, and Adr garnets displaying a wide range in end-member compositions. Coloured outlined circles represent each analyzed point in this study whereas solid coloured circles represent distinct EMPA phases. Black white circles are Uv samples from literature data obtained from Spiridonov et al. (2006), Taran et al. (1994), Knorring (1986), Moroz et al. (2009), Pal and Das (2010), Wildner and Andrut (2001), Arai and Akizawa (2014), and Proenza et al. (1999)...... 65

Figure 3.1.8.1. Apfu distribution of calculated EMPA data for SAR-1, SAR-2, and SKR-1 compared with literature data from Moroz et al. (2009) pts. 1-8, Andrut and Wildner (2001) pts. 9-14, Sawada (1997) pt. 15, Bocchio et al. (2010) pt. 16, and Spiridonov et al. (2006) pts. 17-21, uvarovite samples from various localities in the Ural Mountains of Russia represented as hollow black shapes. The coloured background represents the distinction from studied samples, SAR-1 (light-green), SAR-2 (peach), and SKR-1 (light-blue). a. {X} site partitioning with Ca2+ as the dominant cation. b. [Y] site displaying a gradual increase in Cr3+ and decreasing Al3+. c. (Z) site contain Si4+ as the dominant cation...... 69

Figure 3.1.8.2. Apfu distribution of calculated EMPA data for JTC-1 compared to Novak and Gibbs (1971) Uv sample from Washington, Nevada County, California represented as shapes outlined in black (pt. 26). a. {X} site contains Ca2+ as the dominant cation. b. [Y] site displays a gradual increase in Cr3+ and decreasing Fe3+. The literature data show an average chemical composition of Uv garnet with distinctively high Cr3+ content with trace amounts of Fe3+ apfu, contrasting from the results of JTC-1. c. (Z) site partitioning with Si4+ as the dominant cation...... 72

Figure 3.1.8.3. Apfu distribution of calculated EMPA data for FIN-1 compared with literature data represented as hollow shapes in black. The coloured background display the distinction from literature data samples, Knorring et al. (1986) in white, Amthauer et al. (1976) pt. 11 in orange, Langer et al. (2004) pt. 26 in blue, Diella et al. (2004) pt. 26 in green, Taran et al. (1994) pt. 35 in purple, and Menzer (1928) pt. 50 in light red. a. {X} site contain Ca2+ as the dominant cation. b. [Y] site show a gradual increase in Cr3+ and decreasing Fe3+. c. (Z) site displays Si4+ as the dominant cation...... 73

Figure 3.2.1. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for SAR-1 from Sarany, Urals, Russia. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (640) for the single-phase compared to 3-phase displaying a more accurate fit and reduced difference curve...... 77

Figure 3.2.2. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for SAR-2 from Sarany, Urals, Russia. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (14,4,2) for the single-phase compared to 2-phase displaying a more accurate fit and reduced difference curve...... 82

xi Figure 3.2.3. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for STZ-1 from Switzerland. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single- phase compared to 2-phase displaying a more accurate fit and reduced difference curve...... 85

Figure 3.2.4. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for JTC-1 from Jacksonville, Tuolumne County, California. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single-phase compared to 2-phase displaying a more accurate fit and reduced difference curve...... 90

Figure 3.2.5. Comparison of completed HRPXRD traces for a. single-phase refinement and b. zoomed in trace of JTC*-5s from Jacksonville, Tuolumne County, California. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows sharp symmetrical peaks displaying minimal changes in the difference curve...... 91

Figure 3.2.6. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for FIN-1 from Outokumpu, Finland. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single-phase compared to 4-phase displaying a more accurate fit and reduced difference curve...... 94

Figure 3.3.1. Relationship between a. ; Ca as the dominant {X} site atom and b. Y-O; Cr as the dominant [Y] site atom, both with respect to the a cell parameter (Å). Trend lines are fit to all of the samples studied along with literature data with the exception of the synthetic Uv samples from literature and excluding Uv phases: FIN-6b, c, d, SAR-1b, and SAR-2b. Grs data is taken from Antao (2013) and Adr data from Antao (2013). The remaining literature data are Uv from: Novak and Gibbs (1971), Carda et al. (1994), Sawada (1999), Wildner and Andrut (2001), and Andrut and Wildner (2002)...... 108

Figure 3.3.2. Relationship between a. Z-O; Si as the dominant (Z) site atom and b. ; the average distance for the O atom, all with respect to the a cell parameter (Å). Trend lines are fit to all of the samples studied along with literature data with the exception of the synthetic Uv samples from literature and excluding Uv phases: FIN-6b, c, d, SAR-1b, and SAR-2b. Grs data is taken from Antao (2013) and Adr data from Antao (2013). The remaining literature data are Uv from: Novak and Gibbs (1971), Carda et al. (1994), Sawada (1999), Wildner and Andrut (2001), and Andrut and Wildner (2002)...... 109

xii

CHAPTER 1: INTRODUCTION

1.1 Purpose

For over a century, the occurrence of anomalous birefringent garnet species has attracted the interest of many geoscientists. Past research examined a number of potential causes concerning the origin of optical anisotropy including but not limited to, the distribution of hydrous components within the tetrahedral (Z) site, cation ordering on the dodecahedral {X} and octahedral [Y] sites, and strain derived from lattice mismatch at compositional boundaries.

However, the origin still remains questionable and unclear. Birefringence, a diagnostic optical property characteristic to anisotropic materials and is observed in several end-member garnet species. Uvarovite (Uv) shown in Figure 1.1 is a rare mantle-derived garnet, ideally

Ca3Cr2Si3O12, typically displays clear birefringence possessing additional anisotropic features such as: oscillatory zoning, bow-tie structures, and well-defined extinction positions. What are the internal and structural processes at play causing this phenomenon to occur in uvarovite and many other reported garnet end-member species? Cubic garnet is generally isotropic under cross-polarized light, appearing at full extinction upon 360° stage rotation and should not possess this feature.

This thesis focuses on the crystal chemistry and structure of six birefringent Uv-rich garnets from various localities including: Russia, Switzerland, Finland, and California. The structural trends and chemical compositions of Uv are compared to previous studies and an explanation on the origin of the anomalous birefringence is discussed. Optical microscopy displays distinct anisotropy but XRD analysis reveals no deviation from cubic symmetry. Using electron microprobe analysis (EMPA) along with synchrotron high-resolution powder X-ray

1 diffraction (HRPXRD), in addition to optical microscopy, the chemical compositions and crystal structure reveals that strain caused by the lattice mismatch between boundaries of different phases of uvarovite is the source of the observed birefringence. Furthermore, recent studies on optical anomalies in garnets, closely relate birefringence to split diffraction peaks observed in

HRPXRD traces, interpreted to result from the strain induced birefringence of intergrowths containing slightly different multiple cubic garnet phases (Antao and Klickner 2013, Antao 2015,

Antao et al. 2015), further attribute the cause of birefringence to strain.

1.2 Organization of this Thesis

This thesis is divided into four chapters; an introductory chapter providing background information on the mineral garnet, including its calcium-chromium end-member uvarovite, along with the most accepted proposed causes of optical anisotropy in garnets from the last century. In

Chapter 2, detailed descriptions of each Uv sample are given as well as a brief overview on the experimental techniques used in this study. Chapter 3 comprises of the results obtained from

EMPA and HRPXRD analysis and provides a detailed interpretation into the origin of birefringence in Uv garnet. Lastly, the conclusion is presented in Chapter 4 along with recommendations for possible future investigations. Appendix A comprises of EMPA data of all individual points from each uvarovite sample studied.

Data from this study was presented as posters at: the annual Geological Association of

Canada and the Mineralogical Association of Canada (GAC-MAC) conference in June 2016 in

Whitehorse, Yukon; the annual Roundup AME convention in Vancouver, British Columbia in

January 2017; and the Geoscience Research Exchange (GeoRex) symposium at the University of

Calgary in April 2017.

1.3 Garnet

Garnet belongs to a diverse group of minerals commonly found in numerous metamorphic environments, less common in igneous rocks, and can also be found as detrital grains (Deer et al.

1982). A study by Grew et al. (2013) reports the nomenclature of the garnet supergroup, which constitutes 32 approved species with 5 additional species requiring further review for approval.

They define ‘supergroup’ to incorporate all minerals isostructural with garnet despite the vast combination of elements that can occupy the {X}, [Y], and (Z) sites. However, this thesis does not include information on minerals outside the silicate garnet group. Garnets continue to be of scientific interest because of their unique cubic crystal structure, thermodynamic stability, practical economic uses, and the variation in chemical and physical properties. The cubic crystal structure of garnet can substitute for a multitude of cations with variable sizes and valence states

(Carda et al. 1994). Many synthetic compounds and natural minerals such as diamonds and gold exhibit the same cubic crystal structure. Unlike in nature, laboratory experiments allow us to obtain quantitative information on the possible compositional ranges of silicate garnets using fixed pressures and temperatures enabling the synthesis of these minerals (Geiger 2016).

Secondary raw materials, from recycling of both hazardous and non-hazardous wastes are used to synthesize a uvarovite-based ceramic pigment (Gualtieri et al. 2011). This green pigment exhibits the same structure as garnet and is used for industrial purposes in both bulk stoneware tiles and glazes for fast firing tiles (Gualtieri et al. 2011). Furthermore, many other synthetic garnet species are used for laser technique materials, applications in magneto-ceramics, and as diamond simulants (Andrut et al. 2001).

Silicate garnets with the general chemical formula, {X3}[Y2](Z3)O12, are divided into two classifications: the ugrandite and the pyralspite series (Table 1). In general, the Ca2+ cations

3 occupy the dodecahedral {X} site in ugrandite garnets and include the end-members: grossular, andradite, and uvarovite. Pyralspite garnets contain Al3+ in the octahedral [Y] site and no Ca2+ cations in the dodecahedral {X} site, and are comprised of the following end-members: almandine, pyrope, and spessartine. The dominant cation for the tetrahedra (Z) site is Si4+ for all silicate end-members in the garnet group. Alternating octahedra and tetrahedra form a three dimensional garnet structure with distorted triangular dodecahedra occupying the cavities (Fig.

1.2). Chemical compositional complexities involving solid solution series between different garnet end-members continue to spark the interest of many geoscientists across various disciplines. Compared to the other end-members, the ugrandite garnets display lower specific gravities, lower hardness, and are typically green in colour. Garnets rich in iron and manganese, typical of the pyralspite series often display higher specific gravities, greater hardness, and a distinct red colour. Ugrandite garnets are more likely to display birefringence compared to pyralspites. A better understanding of the crystal structure and chemistry of the garnet species can further enhance the applicability of this diverse mineral group to a wide range of specializations.

Table 1.1. Ugrandite and pyralspite end member garnets Ugrandite Series Pyralspite Series

Andradite (Adr) Ca3Fe2Si3O12 Almandine (Alm) Fe3Al2Si3O12

Grossular (Grs) Ca3Al2Si3O12 Pyrope (Prp) Mg3Al2Si3O12

Uvarovite (Uv) Ca3Cr2Si3O12 Spessartine (Sps) Mn3Al2Si3O12

1.4 Uvarovite Garnet

Uvarovite, ideally Ca3Cr2Si3O12, generally possess an emerald green colour ranging from vitreous cubic to opaque rhombic dodecahedra varieties (Figure 1.1). Natural Uv-rich occurrences are restricted to contact metamorphism and hydrothermal settings; typically associated with serpentinite, chromite, metamorphic limestones, and skarn ore-bodies (Isaac

1965; Proenza et al. 1999). However, Uv has the highest thermal stability range for any end- member garnet below 23kbar and is also stable at atmospheric pressure, allowing the synthesis of this mineral in laboratory settings (Deer et al. 1982; Carda et al. 1994). Uv is generally considered as a gem quality mineral, but due to its size it is too small to be cut into individual stones. Although, quantities of small sparkling crusts of uncut crystals found on matrix are widely used for jewellery, whereas larger and more exquisite specimens are displayed in mineral collections of many museums (Spiridonov et al. 2006). The largest Uv specimens are found in

Outokumpu, Northern Karelia, Finland, which are up to 10 mm with green, exhibiting translucent to opaque rhombic dodecahedral forms (Figure 1.1g to 1.1i; Knorring et al. 1986).

Natural Uv-rich garnet is never found in nature as a pure end-member, but is almost always found in an impure solid-solution series containing significant components of other ugrandite end-members, Grs and Adr.

a d g

2 cm SAR-1 JTC-1 1 cm FIN-1 2 cm

b e h

c 6 mm f 5 mm i 4 mm Figure 1.1. Uvarovite on host rocks from a. Sarany Urals, Russia (SAR-1), d. Jacksonville, California (JTC-1), and g. Outokumpo, Finland (FIN-1). Photographs (2X) of SAR-1 in b. display two deep green shades with moss-like texture on host rock, JTC-1 in e. show diagnostic emerald green colour with light and dark green varieties, and FIN-1 in h. contain large dodecahedral opaque crystals up to 6 mm imbedded in matrix. Magnified Uv crystals (5X) in SAR-1 in c. show a homogenous emerald green colour with some exposed cubic faces, JTC-1 in f. show large euhedral crystals, and FIN-1 in i. display uniform deep green crystal fragments.

1.5 Crystal Chemistry of Uvarovite Garnet

Substitution within the octahedral [Y] site of the ugrandite series consists of three principal cations, Al3+, Cr3+, Fe3+, producing the Grs, Uv, and Adr end-members, respectively. Near Uv end-member compositions are rare in nature, but common solid solution series exist between Grs and less commonly with Adr. Proenza et al. (1999) observed a complete miscibility along the

Uv-Grs solid solution series formed at relatively low pressure and temperatures in the Moa-

Baracoa massif, Cuba. Additionally, Ghosh and Morishita (2011) reported a complete solid solution between Uv-Adr in Rutland Island, India to also have been formed in low temperature and pressure settings.

Solid-solution series also exist between uvarovite and members of the pyralspite series.

Carstens (1973) studied the colour change from red to green in three different pyropes of variable solid solutions between near end-member pyrope, knorringite (Mg3Cr2Si3O12), and uvarovite garnets. Carstens (1973) revealed the colour change is closely related to the total chemical composition of the garnet, specifically caused by the concentration of Cr3+ entering the octahedral [Y] site. Furthermore, the large substituting {X} site Ca2+ ions, expands the Cr-O distance. Cr3+ in the [Y] site give the garnets a green colour, in contrast to pyrope, where a red colour is observed. Similarly, Taran et al. (2008) used electronic absorption spectra analysis on natural dark green Uv (62 mole %) and concluded that increasing pressure can affect the colour of Uv from green to red at 10-4 GPa to 12.92 GPa, respectively. Additionally, Frankel (1959) conducted quantitative colour meaurements on natural powdered Uv and determined that higher iron content corresponds to a deeper green colour, whereas Uv with variable TiO2 content appears as rusty green.

Substitution and impurities of minor and trace elements beyond the principal ugrandite [Y] site cations can be naturally found or synthesized. The presence of impurities within the garnet structure can yield optical textures such as lamellar features or complex sector zoning (Allen and

Buseck 1988). Previous studies on synthetic uvarovite have also been done to show the possibility of cation substitution between rare non ugrandite garnets. For example, Carda et al.

(1994) successfully synthesized Uv using the sol-gel method but Rietveld refinement identified incomplete substitution between Uv and yttruim-aluminum synthetic garnet in the tetrahedral (Z) site deviate from the nominal compositions.

1.6 Crystal Structure of Uvarovite Garnet

Uv is isotropic, possess cubic symmetry, and belongs to the space group Ia3d (Novak and

Gibbs 1971). The general chemical formula of silicate garnet is {X3}[Y2](Z3)O12. The {X},

[Y], and (Z) cations lie on special positions corresponding to the type of oxygen coordination polyhedra. The { } refers to the eight-coordination dodecahedra, [ ] denotes the Figure 1.2. Polyhedra representation of a garnet crystal structure with alternating six-coordination octahedra, and ( ) belongs to the dodecahedra (blue), octahedra (yellow), and tetrahedra (grey) projected down the a four-coordination tetrahedra (Novak and Gibbs axis. Illustration shows a repeating pattern formed by the high number of shared edges 1971). The first garnet structure analyzed was outside the unit-cell (solid black square). by Menzer (1926) using powder methods, and in 1929, Menzer determined the other silicate end- members to be isostructural with grossular. A wide range of cations can occupy each {X}, [Y],

8 and (Z) polyhedra given the right conditions for formation and subtitution to occur. The crystal structure of Uv, Ca3Cr2Si3O12, consists of a three-dimensional framework of alternating SiO4 tetrahedra with corner sharing CrO6 octahedra illustrated in Figure 1.2. (Novak and Gibbs 1971,

Meyer et al. 2009). The CaO8 dodecahedra occupy the cavities within the framework structure resulting in a slightly distorted triangular dodecahedron. Figure 1.2. shows the continuous framework displaying a high percentage of shared edges among the polyhedra producing a tightly compact structure, that gives rise to the high densities (p = 3.5 - 4.3g/cc) and refractive indices (n = 1.70 - 1.94) of garnet (Novak and Gibbs 1971; Deer et al. 1982). Each individual structural site within the unit cell is characterized by its point symmetry and Wyckoff position

(Table 1.2). The {X}, [Y], and (Z) cations lie in special positions (⅛, 0, ¼), (0, 0, 0), (⅜, 0, ¼),

respectively. Oxygen is situated on a general

position coordinated by two dodecahedra, one

octahedra, and one tetrahedra (Figure 1.3.;

Novak and Gibbs 1971).

Table 1.2. Structural symmetry, Wyckoff position, and coordination of Uv garnet (modified after Geller 1967)

Structure formula {X3} [Y2] (Si3) O12 Point symmetry 222 3 4 1 Wyckoff position 24c 16a 24d 96h Coordination to oxygen 8 6 4 Type Polyhedron Triangular Octahedron Tetrahedron Tetrahedron dodecahedron

1.6.1 Dodecahedral {X} Site

The dominant cation for the dodecahedral {X} site in ugrandite garnets is Ca2+ and has special position (⅛, 0,

¼), which is located within the cavities between the tetrahedra and octahedra framework. The polyhedron is slightly distorted resulting in a triangular dodecahedron coordinated with 8 oxygen atoms, comprising two sets of Figure 1.4. Polyhedron model differing four X-O bond lengths (Figure 1.4). In Uv, the of the eight - coordinated triangular dodecahedron {X} shorter unshared bond edge of 2.360 Å with the longer site of garnet projected down an intermediate position between shared bond edge of 2.499 Å yield an X-O bond length all three axes. average of 2.429 Å (Figure 1.3; Figure 1.4c; Novak and Gibbs 1971). The differences between these bond length edges account for the distorted shape of the polyhedra. A characteristic feature of ugrandite garnets is the overbonded nature of Ca2+ containing four edges shared with neighbouring dodecahedra that are longer than its two unshared edges (Wildner and Andrut

2001). The triangular dodecahedron shares 10 out of its 12 edges with neighbouring polyhedra: two edges with SiO4 tetrahedra, four edges with CrO6 octahedra, and the remaining four with

10 corresponding CaO8 triangular dodecahedra (Figure 1.5; Novak and Gibbs 1971; Wilder and

Andrut 2001). In addition, any substitution at the {X} site can influence the bond lengths, bond angles, as well as the stability range because of the large atomic radius and high number of shared edges, compared to octahedral [Y] and tetrahedral (Z) sites have only minimal influence on the general structure. Ugrandites often contain longer dodecahedra-octahedra (X-Y) and octahedra-octahedra (Y-Y) shared edges compared to unshared edges, instead pyralspites exhibit the opposite effect (Ungaretti et al. 1995).

a b c

Figure 1.5. Polyhedra models of dodecahedron edge sharing 10 of its 12 edges with a. four adjacent dodecahedra, b. four octahedra, and c. two tetrahedron.

1.6.2 Octahedral [Y] Site

The octahedral [Y] site cations have ionic radius between 0.5 and 1.05 Å that can be filled by: Mn2+, Mg2+, Al3+,

Cr3+, Fe3+, and Ti4+(Deer et al 1982). Less frequently, the [Y] site can also be occupied by the transition metals Sc, V, Co, Ni, or Zn (Bocchio et al. 2010). Uv contains Cr3+ in the octahedral site coordinated with six oxygen atoms having an average Y-O bond length of 1.985 Å in all directions (Figure 1.6). [Y] site Figure 1.6. Polyhedra model of a six-coordinated [Y] site octahedra are positioned at (0, 0, 0) and share all of its six edges octahedron. The Y-O bond length value of uvarovite is with bordering dodecahedra (Figure 1.7). The ugrandites from Novak and Gibbs (1971). replacement of Al3+ with Cr3+ or Fe3+ cations on the octahedral [Y] site reduces the overbonded nature of the Ca2+ by lengthening the X-O bonds, thus reducing the difference in bond lengths between the two sets of X-O in the dodecahedral {X} site (Wildner and Andrut 2001). Single

Raman spectra study on synthetic uvarovite by

Chopelas (2005) revealed the octahedral [Y] site of

Uv to have a stronger, more rigid framework

compared to the other ugrandite garnets due to

trivalent chromium having three unpaired electrons

resulting in lower energy than the d-orbital level.

Like the dodecahedra, octahedra have longer shared

bond distances compared to the unshared edges Figure 1.7. [Y] site octahedron edge sharing with six neighbouring resulting in octahedral compression along the 3 axis dodecahedra.

12 for ugrandites compared to elongation in pyralspites (Wildner and Andrut 2001). Abu-Eid and

Burns (1976) analyzed the effects of covalency of the Cr-O bond in Uv garnet and determined that with increasing pressure up to 200 kbar, a relatively small decrease in the average Cr-O bond distance by 0.07 to 0.10 % occurs.

1.6.3 Tetrahedral (Z) Site

The principal cation in the tetrahedral (Z) site for all silicate garnets is Si4+ and is bonded to four oxygen atoms (Figure 1.8). The tetrahedral (Z) site is on a special position (⅜, 0, ¼) sharing two edges both with triangular dodecahedron. The mean recorded tetrahedral Si-O bond length in uvarovite is 1.64 Å (Novak and Gibbs 1971). Impurities within the (Z) site occupy vacant sites will often influence the garnet structure to contain minor proportions of rarer end- member garnet species, given the ideal Figure 1.8. Polyhedral conditions required. The term hydrogarnets models of an a. (Z) Site tetrahedron and b. edge are typically more common in the ugrandite sharing with two adjacent dodecahedra. series, which are more hydrous than the The Z-O bond length value of uvarovite is original six end-member species. In from Novak and Gibbs (1971). addition, hydrogarnets are missing the a b tetrahedral (Si4+) site cation, which have been locally replaced by OH- groups consisting of four hydrogen atoms (Geiger

2013).

1.7 Previous Research on Anomalous Birefringent Garnets

Birefringence in garnets was observed over a century ago (Brauns 1891) with no clear explanation to the origin of this phenomenon. Extensive research over the past six decades have attributed the causes of anomalous birefringence to: twinning (Ingerson and Barsdale 1943), cation ordering on the {X} and [Y] sites resulting in a reduction to lower crystal symmetry

(Allen and Buseck 1988; Wildner and Andrut 2001; Shtukenberg et al. 2005), distribution of hydrous components (Allen and Buseck 1988; Andrut et al. 2001), and strain (Hofmeister et al.

1998; by Arai and Akizawa 2014). Slight optical anisotropy in crystals of Uv and Adr was observed by Novak and Gibbs (1971) and used Laue and diffraction symmetry and concluded no violation to the space group Ia3d. Foord and Mills (1978) examined the biaxiality of isotropic crystals to explain the optical anisotropy of different mineral species, including Uv. The reflections examined on X-ray diffraction data indicated no inconsistency from cubic symmetry

(Foord and Mills 1978) and compares well with the results from Novak and Gibbs (1971).

Spiridonov et al. (2006) investigated gem-quality minerals including Uv from the Saranovskoye chromite deposit, Western Urals, Russia, and observed optical anisotropy displaying strong oscillatory zoning features. They briefly attributed the phenomenon to Al and Cr ordering.

Birefringence in uvarovite has only been observed sporadically but all have the same range up to

0.008 (Proenza et al. 1999; Wildner and Andrut 2001; Spiridonov et al. 2006).

1.7.1 Twinning

Ingerson and Barsdale (1943) examined the temperature at which natural birefringent garnet possessing twinning textures would lose its optical anisotropy. Optical microscopy revealed a well-defined banding or twinning pattern parallel to the dodecahedral (110) face on one sample. In-depth analysis in higher magnification detected superimposed herringbone lamellae parallel to the octahedral (111) plane as well as complex mottling textures. Ingerson and Barksdale (1943) proposed the anomalous anisotropy to be the result of reflections from fine polysynthetic twinning, where birefringence intensity is dependent on the thickness of the individual octahedra lamellae. In contrast, many garnet studies with reported birefringence display no sign of twinning (Novak and Gibbs 1971; Allen and Buseck 1988). To propose twinning as a cause for optical anisotropy, twinning features should be present in all birefringent garnet samples that have been studied, including this study. However, twinning is not present in every birefringent Uv crystal examined and therefore cannot cause optical anisotropy in garnets.

Recorded studies of twinning and zoning in uvarovite are sporadic due to its rare occurrence.

Optical microscopy investigations by Proenza et al. (1999) in crossed-polarized light identified complex sector twinning in some uvarovite grains from Cuba and concluded that twinning was not associated to dissolution processes or anomalous birefringence but rather to growth or an internal organization mechanism.

1.7.2 Cation Ordering

Ugrandite garnets exhibit cation ordering in the octahedral [Y] site most commonly between Al3+, Cr3+, and Fe3+, whereas the ordering occurs in the dodecahedral {X} site between

Mn 2+, Mg2+, and Fe2+ in the pyralspite series (Allen and Buseck 1988). Shtukenberg et al.

(2005) suggests that most structure refinements reveal long-range cation ordering of Al3+- Fe3+ and Al3+- Cr3+ within octahedral [Y] sites in the ugrandite series is the main contributor to optical anisotropy. Cation ordering is currently the most widely accepted cause of birefringence in garnets. Shtukenberg et al. (2005) proposed the ‘growth dissymmetrization’ phenomenon, where a preferential site selection between Al3+, Cr3+, and Fe3+ cations occurs in the octahedral [Y] site positions. However, in the cases of near or pure end-member garnets, there is only one dominant

[Y] site cation close to full occupancy, therefore this does not hold true (Antao 2013). An ordered distribution of the [Y] site cation controls the growth face of the atomic structure splitting into two different occupied sites producing a reduction in high order symmetry to either orthorhombic, monoclinic or triclinic systems (Shtukenberg et al. 2005).

Wildner and Andrut (2001) investigated the crystal structures of six uvarovite-grossular garnets and determined that the partial long range Cr3+/Al ordering on the octahedral [Y] site was the most non cubic feature and most likely caused anistropy in garnets. The lattice distortions, violation of reflection conditions, and non-cubic intensity distributions obtained from X-ray diffraction data proved that there was a pronounced reduction in symmetry from the cubic garnet space group Ia3d to either the triclinic space group I1, monoclinic (I2/a), or orthorhombic symmetry (Fddd) (Wildner and Andrut 2001). Moreover, Wildner and Andrut (2001) recognized the most important deviations from cubic symmetry occurred in the CaO8 dodecahedra {X} site. The distortions developed in the bond distances between the shared edges of octahedra and neighbouring dodecahedra is controlled by the Cr/Al site distribution.

Furthermore, Allen and Buseck (1988) linked optical anisotropy to partial substitution ordering on the octahedral site during growth between the dodecahedral {X} site and octahedral

[Y] site. The chemical heterogeneity between {X} and [Y] site cations causes the lattice distortions between the X-O/Y-O interatomic distances and the crystal symmetry reduces the cubic symmetry of garnet, which in turn causes the birefringence. Similarly, Meyer et al. (2009) evaluated Uv-Adr solid solutions into lower symmetry from cubic to tetragonal, orthorhombic, monoclinic, trigonal, and triclinic crystal systems. They observed the angular deviation from 90° cubic symmetry was always very small, up to 0.1°, and additionally the largest difference in a, b, and c cell parameters was 0.004 Å. The results from symmetry reduction studies show consistent results that are well within error, and are negligible, revealing no drastic deviation from high cubic symmetry.

1.7.3 Hydrous Components

The tetrahedral (Z) site is dominated by the silicon cation, yet hydrogen atoms can enter the crystal structure and substitute for Si4+, which is known as the hydrogarnet substitution. The

4+ 4+ 4- 4- Si tetrahedral cations are replaced by the 4H such that (SiO4) is balanced by (O4H4) (Allen and Buseck 1988). In addition, Andrut et al. (2001) states that the (O4H4) hydrogarnet substitution is not the only way for hydrogen to enter the crystal structure of garnets and the presence of [SiO3(OH)] tetrahedra groups is another alternative. Furthermore, different OH incorporation mechanisms besides the hydrogarnet substitution can detect low garnet OH contents (Andrut et al. 2001). This may apply more to the pyralspite series considering they are nominally anhydrous with variable species containing minimal OH content compared to the calcic garnets. Determining the hydrous component of garnets is important because minor water content in anhydrous phases can significantly impact their physical and chemical properties, which can lead to deformation mechanisms (strain), and can possibly cause anisotropy in garnets

(Wildner and Andrut 2001). Uvarovite, although part of the ugrandite series, typically does not contain water, unlike hydrogrossular and hydroandradite, which can contain large amounts (10-

15%) of water (Pal and Das 2010).

Allen and Buseck (1988) conducted spectroscopy studies to determine if optical birefringence is caused by low-symmetry distribution of OH groups. Results revealed the distribution of OH groups to be variable from point to point in a sample, yet decrease from the core to the rim of a crystal. They stated that the water content decreases progressively in correlation to crystal growth with a dramatic rise in water near the end stages. Annealing experiments at 870 °C for 40 hours identified the disorder, a depleted OH component, and a loss of birefringence on anisotropic garnet indicating a reduction to isotropy. However, heating up to

800 °C displayed depleted water content; however, the birefringence remained visible. As a result, Allen and Buseck (1988) reported an inconsistency and demonstrated that the hydrous component is not responsible for the optical anisotropy in garnets. Andrut and Wildner (2001) further corroborate this theory, such that they conducted annealing experiments with incorporated hydrous groups, and had detected no significant changes in birefringence upon heating but anisotropic behaviour remained on two Uv samples.

1.7.4 Compositional Heterogeneity

Optical features such as oscillatory zoning and growth sector zoning are representative of chemical inhomogeneities (Ivanova et al 1998; Pollock et al. 2001; Badar et al. 2012). Zoning textures in minerals are important because they represent a record of the chemical and mineralogical changes that occurs during the crystallization process. Compositional zoning is indicative of a core with an initial crystal composition exhibiting distinct and sharp contacts between newer layers of differing proportions. Proenza et al. (1999) studied birefringent Uv in veins of chromitite pods that display oscillatory zoning, identified by differences in hues of green as well as complex sector twinning. Euhedral crystals studied exhibited rhombic dodecahedra

{110} crystal faces with variations in colour attributed to variable Uv and Grs molar proportions.

An internal process linked to strain and symmetry was the most feasible cause of oscillatory zoning opposed from external forces such as chemical changes or flow rates (Ivanova et al.1998;

Proenza et al. 1999). Knorring (1951) observed both optically isotropic and anisotropic uvarovites from Karelia, Finland and noted many excellent specimens exhibiting compositional zoning, mainly in the central anisotropic core. No further interpretation of the birefringence was given, however, the difficult nature of anisotropic uvarovite prevented Knorring (1951) to conduct refractive index determination.

A more recent study by Arai and Akizawa (2014), reported oscillatory concentric zoning within inclusion filled uvarovite grains. They suggest the chemical zonation of uvarovite was derived from a progressive outward growth process, recording periodic changes in the Cr content distinctive of sharp changes in boundary contacts. Badar et al. (2012) examined the relationship between the surface features and internal texture of garnet. Results determined that optical properties differ from one growth face to another, and are influenced by the variation in growth

19 orientation in relation to growth rate. Hofmeister et al. (1998) studied 48 garnets using optical microscopy with EMPA and stated that birefringence was attributed to residual strain.

Retardation may be preserved as strain if the crystal is subjected to deviatoric stress during formation or after crystallization (Hofmeister et al. 1998). They proposed the internal strain generated from the mismatch in size between the Ca2+ and Mg2+ cations in the dodecahedral {X} site, causes the distortion thus leading to optical anisotropy. Internal strain can arise from the dynamic disorder of Mg2+, which increases due to the expansion of the dodecahedron from increased levels of Ca2+. Furthermore, Hofmeister et al. (1998) concluded that strain is independent and does not affect the crystal system of the birefringent garnets, which all 48 samples maintained its cubic symmetry, unlike cation ordering. Strain is considered to be another widely accepted cause to the origin of birefringence in garnets.

1.7.5 Additional Cubic Phase Intergrowths

Many past studies have conducted experiments on garnet crystal structure analysis by conventional powder (PXRD) and single crystal (SXTL) X-ray diffraction methods (Allen and

Buseck 1988; Ivanova et al. 1998; Andrut and Wildner 2001; and Antao 2013). However, the introduction of the HRPXRD technique within the last decade has enabled scientists to examine difficult powdered crystalline materials more easily, rapidly, and most of all with enhanced higher resolution, superior to that of SXTL methods (Antao 2008). HRPXRD analysis is capable of examining: multiple samples at once, specimens that do not form as single crystals, samples possessing intergrowths characterized by exsolution or zoning textures, as well as superstructures

(Antao 2008). The superior high-resolution of HRPXRD is able to detect for additional phases of minerals occurring as mixtures of fine scale intergrowths. Recently, crystal structure analysis

20 on several garnet end-member species, specifically: Grs, Adr, as well as hydrogarnet varieties have identified the existence of secondary fine scale cubic phase intergrowths mixed together.

This is a result from a lattice mismatch inducing internal strain within the crystal structure and is another proposed cause of the anomalous birefringence phenomenon (Antao and Klickner 2013,

Antao 2015, Antao et al. 2015). The findings of this study are similar to previous birefringent garnet research analyzed by HRPXRD such that multiple cubic phases of coexisting uvarovite intergrowths of each sample were detected and further elaborated in the discussion portion of

Chapter 3.

CHAPTER 2: EXPERIMENTAL TECHNIQUES

2.1 Sample Description

Six optically anisotropic Uv garnets were analyzed using optical microscopy, EMPA, and synchrotron HRPXRD. Three samples are from Russia; two from the Sarany, Ural Mountains region (SAR-1 and SAR-2) while the third Uv specimen comes from the Saranovskii chromite mine (SKR-1). An Uv-Grs-Adr from Zermatt, Switzerland (STZ-1), Uv-Adr from Jacksonville,

Tuolumne County, California (JTC-1), and Uv-Grs from Outokumpu, Finland (FIN-1) comprise the other three samples. Uv specimens used in this study exhibit the diagnostic emerald green colour and contain perfectly preserved euhedral crystal forms displaying cubic and rhombic dodecahedral faces. Uv crystals were handpicked under a stereomicroscope and pure euhedral crystals free of impurities were chosen for HRPXRD analysis. Pure Uv crystals are ideal because an X-ray diffraction (XRD) trace will record the crystal structure information on all phases present and impure unknown phases would reveal unindexed peaks. Due to the limited availability of pure Uv crystals, the best specimens were chosen for HRPXRD, while other well- formed crystals containing minor but distinct impurities were used for EMPA and optical microscopy investigations.

2.1.1 SAR-1, SAR-2, and SKR-1

SAR-1 (Figure 1.1.1a to c) contains emerald green cubic crystals and ranges in size from

0.5 to 2 mm with some fragments exhibiting a black chromite core. The Uv samples comprise two crustal groups of emerald green crystals display a druzy lustre as seen from the host rock.

However, upon closer inspection at 5X magnification (Figure 1.1.1c), one dominant homogenous green colour is observed. SAR-2 crystals are larger in size compared to SAR-1, up to 3 mm with some fragments enclosed in quartz (Figure 2.1.1a). SAR-2 possesses the same diagnostic green colour as SAR-1; however, the crystals display a more dodecahedral form with opaque varieties.

SKR-1 is similar in size and shape to SAR-2, up to 3.5 mm, possessing the same distinctive deep green colour (Figure 2.1.1c) with clear inclusions of a black chromite core. Spiridonov et al.

(2006) investigated gem minerals from the Saranovskoye chromite deposit, the general locality where all three SAR-1, SAR-2, and SKR-1 Uv samples originate. They also observed some Uv samples to contain black chromite cores and traces of quartz overgrowths along the rhombic dodecahedra crystal edges similar to that found in SAR-1, SAR-2, SKR-1.

SAR-2 XPL STZ-1 SKR-1

a 2 mm b 10 X c 2 mm

2.1.2 FIN-1, JTC-1, and STZ-1

FIN-1 (Figure 1.1.1g. to i.) has the largest Uv crystals in this study with sizes varying from 3 to 6 mm. FIN-1 has well exposed dodecahedral faces exhibiting an earthy dull opaque lustre, and is found in clusters in various isolated areas of the host rock. FIN-1 contains traces of calcite and chalcopyrite and is consistent with the associated minerals from Knorring’s (1951)

Uv samples also from the Outokumpu, Finland. JTC-1 (Figure 1.1.1d. to f.) crystals exhibit a glassy lustre ranging from 0.5 to 3 mm and are the only Uv crystals in this study to exhibit two different shades of green within the same sample. Many crystals show a darker shade of emerald green (JTC-1) while the other end exhibits only a tint of green, almost colourless and will be later referenced to JTC*-5s. The drastic difference in colour of JTC-1 crystals led to separating

Uv crystals for individual EMPA and HRPXRD analyses. STZ-1 crystals are 3 to 5 mm; possess a dull earthy green lustre with a complex internal structure resulting in tiny broken crystal fragments within the larger grain (Figure 2.1.1b.).

2.2 Optical Microscopy

Uvarovite crystals from each sample were chosen based on high quality and purity for polished thin sections in addition to EMPA and Synchrotron HRPXRD experiments. Thin sections containing several crystals of each Uv sample were made to observe the optical anisotropy. Both reflected and transmitted light microscopy analysis revealed all samples to be weakly birefringent. Plane-polarized light (PPL) revealed the distinctive emerald green colour and high relief of Uv garnet with a few crystals showing faint but visible zones of extinction boundaries in crossed-polarized light (XPL) in SKR-1 (Figure 2.2.1a). Many samples also

24 display additional non-cubic optical features such as zoning (Figure 2.2.2f), bow-tie structures

(Figure 2.2.1), and well-defined extinction positions alternating throughout stage rotation (Figure

2.2.2). Cubic Uv garnet is isotropic and should not possess these optical anisotropic features.

SKR-1 PPL XPL

2 mm a b c

Figure 2.2.1. SKR-1 viewed under 10X magnification in a. PPL image displaying deep greenc colour, an XPL view in b. displaying well defined extinction positions and in c. a fully illuminated ‘bowtie’ twinning structure is observed.

JTC-1 PPL

1 mm a 0.5 mm b 0.5 mm c XPL

d e f

g h i

j k l

Figure 2.2.2. JTC-1 displays faint green Uv garnet crystal fragments in PPL from a. to c. In d. to k. XPL images revealing optical anisotropic features of distinct zoning (f., h., and k.) with anomalous alternating extinction positions within a 360° stage rotation viewed under 10X magnification.

2.3 Electron Microprobe Analysis (EMPA)

EMPA is an analytical particle beam technique is used to excite characteristic X-rays to determine the chemical composition of selected areas of solid material (Reed 2005). Six birefringent Uv specimens were loaded on to two discs and firmly secured with epoxy resin.

Using sand paper (coarse for P400 and fine for P60) and diamond abrasives (coarse for 9 µm; medium for 6 µm; fine for 3 µm; and very fine for 1 µm), the discs were polished to expose the crystals to the surface. After each progressively finer abrasive, the disc was washed and cleaned in an ultrasonic bath to remove remnants of polishing material. To eliminate the imperfections caused by topographic effects and microscopic scratches, the disc needed to be flat and well polished (Reed 2005). Lastly, a conductive layer of carbon was coated on to the discs prior to

EMP analysis. The JEOL JXA-8200 electron microprobe in the Department of Geoscience at the University of Calgary was used to analyze the six Uv garnets in this thesis. Quantitative elemental analysis was operated using a beam diameter of 5 µm, an accelerated voltage of 15 kV, and a beam current of 30 nA. Additionally, Backscattered Electron (BSE) images were taken and revealed some crystals containing other anisotropic features that were not observed with optical microscopy containing variable differences in contrasts, zoned bands, and inclusions of calcite, quartz, and chromite.

Instrument calibration is necessary to accurately identify the various cations present. A combination of minerals were used as standards, include the following: almandine (Si4+ and

2+ 4+ 3+ 3+ 3+ 2+ 3+ Fe ), rutile (Ti ), spessartine (Al and Mn ), chromite (Cr ), grossular (Ca ), V2O3 (V ), and almandine-pyrope (Mg2+). A total of eight points were analyzed for each Uv crystal located across the length of each specimen, especially along differences in contrasts of zoned bands while avoiding uneven, scratched, and inclusion filled areas. The compositional data collected

27 from EMP analysis is reported as oxide wt. % to calculate the molar proportions of garnet end- members using the Excel spreadsheet developed by Locock (2008). The structural formula of garnet was evaluated on the basis of eight cations and twelve oxygen atoms per formula unit

(apfu) and the proportions are divided into 29 possible end-members. Muhling and Griffen

(1991) also generated a procedure for evaluation of garnet end-member compositions, however, their method differs in their treatment of Cr3+, resulting in the under estimation of uvarovite and inversely inflating the quantity of knorringite (Locock 2008).

2.4 Synchrotron High-Resolution Powder X-Ray Diffraction (HRPXRD)

Six Uv samples, including JTC*-5s but excluding SKR-1, were analyzed by HRPXRD at beamline 11-BM, Advanced Photon Source (APS), Argonne National Laboratory (ANL). Each

Uv specimen was finely crushed and ground into a powder using a quartz pestle and mortar and loaded into a Kapton capillary tube (0.8 mm internal diameter) for Synchrotron HRPXRD experiments. Epoxy was placed in one end to prevent powder loss during loading, while glass wool fibres are used to seal the other. During the experiment, each sample was rotated at a rate of 90 rotations per second. HRPXRD data were collected at 23°C using a λ of 0.41389(6) or

0.41423(7) Å, with a maximum 2θ range of 50°, a step size of 0.001°, and a step time of 0.1 second/step. HRPXRD traces were obtained by using twelve silicon (111) crystal analyzers, allowing for enhanced detector efficiency, superior angular resolution and accuracy, high quality precision, and accurate diffraction peak positions.

2.4.1 Rietveld Structure Refinement

Analyses of HRPXRD traces were performed with the GSAS program (Larson and Von

Dreele 2000) using the EXPGUI interface (Toby 2001) and the crystal structure was obtained by using the Rietveld refinement method (Rietveld 1969). The initial crystal structure data including cell parameters, space group (Ia3d), and atom coordinates were taken from Andrut and

Wildner’s (2002) Uv sample, Uvasyn-22. All HRPXRD traces were first examined as a single isotropic phase and all but one (JTC*-5s) showed noticeable evidence of additional cubic phases.

The HRPXRD results for single and multi-phase refinements are compared, tabulated, and discussed in Chapter 3.

To prevent divergence, the refinement was performed using a progressive sequence of one parameter at a time per phase, including: scale factor, background, cell, zero offset, profile terms, atomic positions, site occupancy, and isotropic displacement parameters. Examination of the refinement using “liveplot” continued until the observed and calculated profiles were superimposed on one another resulting in an accurate fit of the peaks with minimal differences, indicating the correct HRPXRD unit cell parameters were determined. The detection of additional phases was observed by the appearance of asymmetrical peaks and peak broadening throughout the trace. The sequence of parameters began with scale factor for single phase or phase fractions if determining the occurrence of multiple phases. Subsequently, zero offset and background parameters follows and was modeled using Shifted Chebyschev (function type 1) with 10 terms. The reflection peak profile (type-3) is refined afterwards using the terms GW,

GV, GU, LX, and LY to accurately fit the shape and size of the peaks. Atomic coordinates for

X, Z, were refined, however, Y was not since the coordinates are all zero. The oxygen atom, which is situation on a general position, was also refined. The isotropic displacement parameters

(U) were constrained for the additional phases of Uv and were all refined together resulting in the same U for each corresponding dominant atom of each phase. Considering the high sensitivity of the atomic coordinates (X), isotropic displacement parameters (U), and site occupancy (F) parameters, are refined towards the end. The diffraction traces for each Uv sample show no data below 3° 2θ and was therefore deleted accordingly.

CHAPTER 3: RESULTS AND DISCUSSION

3.1 Electron Microprobe Analysis (EMPA) Results

Six birefringent ugrandite garnet samples were analyzed using EMPA. The oxide weight percentages were obtained with the JEOL JXA-8200 electron microprobe and analyzed with an

Excel spreadsheet created by Locock (2008) by calculating atom per formula unit (apfu) and the molar proportions of garnet end-members. The apfu and end-member composition of each phase of six ugrandite garnet samples are given in Table 3.1.0. A detailed summary of EMPA data for each sample includes the raw electron microprobe oxide percentage data, apfu; on the basis of twelve oxygen atoms, site occupancy factor (sof) derived from the chemical analyses of the dominant neutral atom in the {X}, [Y], and (Z) sites, and lastly the total number of electrons in a formula unit, F(000), all averaged into representative phases and listed in Tables 3.1.1 to Table

3.1.6. These phases are compared to the phases found with HRPXRD results (Chapter 3.2).

Minimums of 15 points per sample were taken for EMP analyses with a total of 72 selected points are provided in Appendix A (Table A1.1 to Table A1.6). Examination of the results from

Appendix A reveals a wide distribution of Uv end-member compositions formed from a solid solution series with Grs and Adr, consisting of variable proportions of cations across each studied sample.

For all the samples in this thesis, the dominant atom in the {X} site is Ca with minor Mn2+ and Mg. The [Y] site contains the most substitution where Cr3+ occupies the majority of the site and variable Al3+ and Fe3+ cations fill the remaining occupancy with trace amounts of Ti4+and

V3+ cations and small amounts of Mg and Si defects were also detected. Si is the dominant (Z) site cation with small amounts of Al3+ atoms. Natural occurring Uv is never found in nature as a

31 pure end-member and is mostly found in a solid solution series with Grs and/or Adr, which is consistent with the EMPA results in this study. Minor pyralspite series garnets (Py, Sps, and

Alm) are found in negligible amounts in samples STZ-1 and FIN-1. Goldmanite, schorlomite, and morimotoite are also present in variable proportions in all samples with the exception of

SAR-1 and the background of these minerals is explained in Chapter 3.1.2. Due to the nature of the octahedral [Y] site comprising the most substitution in ugrandite garnets, the tables are sorted based on increasing Cr3+ apfu in the [Y] site, resulting in an increased Uv end-member. Some

BSE images indicate contrasts in composition of coexisting Uv phases while others indicate zoned bands or oscillatory zoning that optical microscopy could not detect.

Table 3.1.0. Representative chemical and garnet end-member compositions for each phase of the six samples of ugrandite garnet Sample Phase {X-site} [Y-site] (Z-site) End-Member 2+ 3+ SAR-1 1 {Ca2.96Mn 0.01}Σ2.97 [Al1.14Cr0.79Fe 0.07Si0.02Ti0.01]Σ2.03 (Si3.00)O12 Uv39Grs57Adr3 2 {Ca Mn2+ } [Al Cr Fe3+ Si Ti ] (Si )O Uv Grs Adr 2.97 0.01 Σ2.98 0.99 0.94 0.05 0.03 0.01 Σ2.02 3.00 12 48 49 2 3 {Ca } [Cr Al Fe3+ Si Ti ] (Si )O Uv Grs Adr 2.97 1.12 0.83 0.04 0.02 0.01 Σ2.02 3.00 12 56 42 1 3+ SAR-2 1 {Ca3.06} [Cr1.16Al0.58Ti0.12Fe 0.05V0.03Mg0.01]Σ1.94 (Si2.95Al0.05)Σ3.00O12 Uv58Grs29Adr3 2 {Ca Mn2+ } [Cr Al Ti Fe3+ V Mg ] (Si Al ) O Uv Grs Adr 3.04 0.01 1.25 0.53 0.8 0.06 0.02 0.01 Σ1.95 2.95 0.05 Σ3.00 12 62 26 3 3+ *1 SKR-1 1 {Ca3.08} [Cr1.20Al0.51Ti0.12Fe 0.06V0.02Mg0.01]Σ1.92 (Si2.89Al0.12)Σ3.00O12 Uv60Grs25Sch5 2 {Ca } [Cr Al Ti Fe3+ V Mg ] (Si Al ) O Uv Grs Sch 3.09 1.36 0.35 0.11 0.06 0.02 0.01 Σ1.90 2.86 0.15 Σ3.00 12 68 17 5 2+ 3+ STZ-1 1 {Ca2.94Mn 0.03Mg0.01}Σ2.98 [Al1.06Fe 0.50Cr0.44Ti0.02]Σ2.01 (Si2.99Al0.01)Σ3.00O12 Uv22Grs51Adr24 2 {Ca Mn2+ Mg } [Cr Al Fe3+ Ti Si ] (Si Al ) O Uv Grs Adr 2.96 0.02 0.01 Σ2.99 0.87 0.69 0.43 0.01 0.01 Σ2.01 2.99 0.01 Σ3.00 12 43 34 21 3+ JTC-1 1 {Ca2.98} [Fe 1.76Cr0.17Al0.05Ti0.02Si0.01]Σ2.01 (Si2.99Al0.01)Σ3.00O12 Uv9Adr88Grs2 2 {Ca Mg Mn2+ } [Fe3+ Cr Al Ti Si Mg ] (Si Al ) O Uv Adr Grs 2.99 0.01 0.01 Σ3.01 1.29 0.61 0.06 0.02 0.01 0.01 Σ2.00 2.99 0.01 Σ3.00 12 30 64 3 2+ 3+ *2 FIN-1 1 {Ca2.92Mn 0.05Mg0.04}Σ3.00 [Al0.98Cr0.92Fe 0.03Ti0.03Mg0.03V0.01]Σ2.00 (Si2.98Al0.02)Σ3.00O12 Uv46Grs46Mmt3 2+ 3+ 2 {Ca2.92Mn 0.04Mg0.04}Σ3.00 [Cr1.12Al0.79Fe 0.03Ti0.02V0.01Mg0.01Si0.01]Σ2.00 (Si3.00)O12 Uv56Grs37Adr2 2+ 3+ 3 {Ca2.93Mn 0.03Mg0.3}Σ2.99 [Cr1.35Al0.58Fe 0.03Ti0.01V0.01Mg0.01Si0.01]Σ2.01 (Si2.99Al0.01)Σ3.00O12 Uv68Grs27Adr1 2+ 3+ 4 {Ca2.88Mn 0.04Mg0.4}Σ2.96 [Cr1.43Al0.54Si0.04Fe 0.03Ti0.01]Σ2.04 (Si3.00)O12 Uv71Grs24Sps1 *Sch=Schorlomite-Al and Mmt= Morimotoite-Mg

3.1.1 SAR-1

Based on the EMPA data obtained, SAR-1 is a solid solution series between Uv and Grs and is representative of three phases derived from seven analyzed EMPA points. The compositions for each phase of SAR-1 are as follows (Table 3.1.0), Phase-1:

2+ 3+ {Ca2.96Mn 0.01}Σ2.97[Al1.14Cr0.79Fe 0.07Si0.02Ti0.01]Σ2.03(Si3.00)O12; Uv39Grs57Adr3; Phase-2: {Ca2.97

2+ 3+ Mn 0.01}Σ2.98[Al0.99Cr0.94Fe 0.05Si0.03Ti SAR-1 a b

0.01]Σ2.02(Si3.00)O12;Uv48Grs49Adr2 ; and

3+ Phase-3: {Ca2.97}[Cr1.12Al0.83Fe 0.04Si

0.02Ti0.01]Σ2.02(Si3.00)O12; Uv56Grs42 Adr1.

BSE images indicate sharp-zoned BSE Al boundaries occurring in three crystals of 100 µm c d SAR-1 (Figure 3.1.1.1a, 3.1.1.2d, and

3.1.1.3d). The composition of Phases 1 to 3 increases from Uv39 to Uv56 whereas the Grs composition decreases Cr Mg from Grs57 to Grs26. Examining Figure 3.1.1.1. a. BSE image of SAR-1 displaying analyzed points one to seven in subtle variations in contrast throughout the crystal fragment. Elemental maps of b. Al, c. Cr, and d. Appendix A (Table A1.1), Cr2O3 wt. % Mg. Distinct zoning is evident in the BSE, Al, and Cr images, while Mg shows no feature. EMPA ranges from 12.58 to 18.01%. The obtained from the points labeled are given in Appendix A (Table A1.1). The scale bar in a. largest variations in cation apfu occur represents 100 µm. in the [Y] site between Al3+ from 0.363 to 0.359 apfu Cr3+. The seven analyzed points gives rise to three phases of different Uv mole % compositions. Points one and two correspond to phase-1

(Table 3.1.1.2), which contains the lowest Cr3+ apfu located on the rim of the crystal (Figure

3.1.1.1a). Points three to five represents phase-2, located around the core, and lastly points six and seven represents phase-3 and are situated directly on the zoned band of the crystal and comprises the highest Uv compositions in SAR-1. From the BSE image (Figure 3.1.1.1) Uv compositions increase inwards from the rim of phase-1 (Uv39) to the core of phase-2 (Uv48) with the highest Uv composition located on the darker zoned band of phase-3 (Uv56).

a PPL b XPL

SAR-1

c REFL d BSE

Chr

Inc 200 µm

a b

SAR-1 PPL XPL c d Chr

REFL BSE 200 µm

3.5 a {X} site 3.0

) 2.5 , Mg

2+ 2.0 Phase 1 Phase 2 Phase 3

1.5

(Ca, Mn (Ca, Ca 1.0 Mn2+ apfu

0.5 Mg

0.0 1 2 3 4 5 6 7 1.4 b [Y] Site

1.2

1.0

0.8 Cr , Al, Si, Ti, Mg) Ti, Al, Si, ,

3+ 0.6 Fe3+ Al 0.4 Si (Cr, Fe (Cr, Ti 0.2 apfu Mg

0.0 1 2 3 4 5 6 7 3.5 c (Z) site 3.0

2.5

2.0

(Si, Al) (Si, 1.5 Si Al apfu 1.0

0.5

0.0 1 2 3 4 5 6 7 Points

Figure 3.1.1.4. Apfu distribution from EMPA results for seven analyzed points of SAR-1. a. {X} site partitioning with Ca2+ as the dominant cation. b. [Y] site displaying a gradual increase in Cr3+ and decreasing Al3+ with a crossover between points 4 and 5. c. (Z) site contain Si4+ as the dominant cation.

Table 3.1.1. EMPA of three phases of Uv in SAR-1 and two phases in SAR-2 from Sarany, Urals, Russia Oxide (wt. %) SAR-1 SAR-2 Phase-1 Phase-2 Phase-3 Phase-1 Phase-2

Avg.(1-2) Avg.(3-5) Avg.(6-7) pt.1 Avg.(2-4) SiO 38.30 38.13 37.62 35.48 35.26 2 TiO 0.20 0.21 0.20 1.85 1.33 2 Al O 12.32 10.61 8.81 6.39 5.91 2 3 Cr O 12.63 15.10 17.70 17.65 18.85 2 3 V O 0.00 0.00 0.00 0.39 0.34 2 3 Fe O / calc 1.11 0.79 0.64 0.84 0.96 2 3 MnO 0.07 0.08 0.06 0.01 0.07

MgO 0.00 0.02 0.01 0.05 0.06

CaO 35.12 34.93 34.60 34.28 34.06

Σ (calc) 99.72 99.86 99.63 96.95 96.85

Recalculated (wt. %)

final Fe O 1.11 0.79 0.64 0.84 0.96 2 3 final MnO 0.07 0.08 0.06 0.01 0.07

Σ 99.72 99.86 99.63 96.95 96.85

Cations for 12 O atoms

Ca 2.967 2.969 2.973 3.057 3.048

Mn2+ 0.005 0.006 0.004 0.001 0.005

Mg 0.000 0.002 0.001 0.000 0.000

ΣX 2.971 2.976 2.978 3.058 3.053

Cr 0.787 0.947 1.122 1.161 1.245

Al 1.144 0.992 0.830 0.580 0.528

Fe3+ 0.066 0.047 0.038 0.053 0.061

Ti 0.011 0.013 0.012 0.116 0.083

Mg 0.000 0.000 0.001 0.006 0.007

V 0.000 0.000 0.000 0.026 0.023

Si 0.020 0.025 0.019 0.000 0.000

ΣY 2.029 2.024 2.022 1.942 1.947

Si 3.000 3.000 2.997 2.953 2.946

Al 0.000 0.000 0.003 0.047 0.054

ΣZ 3.000 3.000 3.000 3.000 3.000

EMPA X sof 0.991 0.992 0.993 1.019 1.018

EMPA Y sof Cr 0.750 0.781 0.818 0.834 0.849

EMPA Z sof 1.000 1.000 1.000 0.999 0.999

F(000) 138 139 141 143 144

End-Member mole %

Uvarovite 39 48 56 58 62

Grossular 57 49 42 29 26

Andradite 3 2 1 3 3

Schorlomite-Al 0 0 0 2 3

Goldmanite 0 0 0 1 1

Morimotoite-Mg 0 0 0 1 1

Remainder 2 1 1 6 4

Σ 100 100 100 100 100

Quality Index Good Good Good Poor Poor Detailed analysis of individual points of SAR-1 and SAR-2 are given in Appendix A (Table A1.1 and A1.2 respectively).

3.1.2 SAR-2

3+ The compositions of SAR-2 are as follows, Phase-1: {Ca3.06}[Cr1.16Al0.58Ti0.12Fe 0.05

2+ V0.03Mg0.01]Σ1.94(Si2.95Al0.05)Σ3.00O12; Uv58Grs29Adr3; and Phase-2: {Ca3.04Mn 0.01}Σ3.05[Cr1.25Al0.53

3+ Ti0.8Fe 0.06V0.02Mg0.01]Σ1.95(Si2.95Al0.05)Σ3.00O12; Uv62Grs26Adr3 (Table A1.2). Changes in contrast of light and dark areas show a marked oscillatory-zoned pattern parallel to the dodecahedral crystal faces as evident in both the BSE images of SAR-2 (Figure 3.1.2.1 and 3.1.2.2). Phases 1 and 2 increases from Uv58 to a maximum of Uv62 whereas the grossular end-member decreases from Grs29 to Grs26. Analyzed points one to four (Appendix A; Table A1.2) are distributed between two crystals (Figure 3.1.2.1 and 3.1.2.2) exhibit prominent birefringence. Point one is representative of phase-1 and PPL a XPL b is located at the darkened area near the core of Figure

3.1.2.1. Points two to four constitute phase-2 where point SAR-2 two is the darkened area near REFL c BSE d the core (Figure 3.1.2.2a).

Points three and four are positioned in the dark area in between the core and the rim Inc 300 µm of the crystal (Figure Figure 3.1.2.1. SAR-2 crystal A illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence 3.1.2.1a). Increasing Uv c. Reflected light image with prominent oscillatory zoning and inclusions and d. BSE image shows EMPA points labeled composition starts from the are given in Appendix A (Table A1.2). The scale bar in d. represents 300 µm. center and ends at the edge of

the crystal.

The Cr2O3 wt. % in SAR-2 from 17.65 to 19.18% is drastically larger than the majority of the targeted points in SAR-1 while the Al2O3 wt. % from 6.39 to 6.02% is much lower than all

3+ points in SAR-1. This larger difference in Cr2O3 and Al2O3 of SAR-2 results in more Cr entering the octahedral [Y] site with fewer sites for Al3+ to occupy, resulting in a higher Uv end- member mole % than SAR-1. The maximum variation in cation apfu occurs in the [Y] site with

0.108 Cr3+ from 1.161 to 1.269, followed by 0.031 Al3+ apfu from 0.580 to 0.549 apfu. Both

SAR-1 and SAR-2 comprise of a solid-solution series between Uv and Grs with very minor Adr.

However, SAR-2 contains additional trace amounts of TiO2 and V2O3, which can indicate the occurence of Goldmanite, Schorlomite-Al, and Morimotoite-Mg. According to Locock (2008),

3+ Goldmanite has a chemical formula of Ca3V2Si3O12, where the V cations can occupy the [Y]

4+ site. Schorlomite-Al (Ca3Ti2SiAl2O12) can form when excess Ti cations in the [Y] site and both Si4+ and Al3+ residing in the (Z) site form together. In contrast, morimotoite-Mg

(Ca3TiMgSi3O12) contains both Ti and Mg cations, occupying vacancies in the [Y] site. Since many cations can substitute within the [Y] site for ugrandites, these rare end-members can occur given the ideal temperature and pressure conditions if excess atoms are leftover after formation of the dominant garnet end-member.

a b

SAR-2 PPL XPL c d 500 µm

Inc

REFL BSE Figure 3.1.2.2. SAR-2 displaying a. deep green colour in PPL b. XPL image displaying birefringent areas c. Reflected light image with prominent oscillatory zoning in the crystal and d. BSE image shows with EMPA points labeled are given in Appendix A (Table A1.2.). The scale bar in d. represents 500 µm.

3.5 a {X} site 3.0

) 2.5 2+

2.0 Phase 1 Phase 2 (Ca, Mn (Ca, 1.5 apfu 1.0 Ca 0.5 Mn2+ Mg

0.0 1 2 3 4 1.6 b [Y] site

1.4 Cr

1.2 Cr

, Mg, V) , Mg, Fe3+

3+ 1.0 Al 0.8 V Ti 0.6 Mg

(Cr, Al, Ti, Fe Ti, Al, (Cr, 0.4 Al

apfu 0.2

0.0 1 2 3 4 3.5 c (Z) site 3.0

2.5

2.0 Si (Si, Al) (Si, 1.5 Al

apfu Fe3+ 1.0

0.5

0.0 1 2 3 4 Points

3.1.3 SKR-1

The calculated chemical data from the EMP analyses of seven targeted points determined

SKR-1 to have two representative phases of an Uv-Grs solid solution. Phase-1 is an average of

3+ points one to six: {Ca3.08}[Cr1.20Al0.51Ti0.12Fe 0.06V0.02Mg0.01]Σ1.92(Si2.89Al0.12)Σ3.00O12; Uv60Grs25

3+ Sch5Adr3 while Phase-2 is comprised of point seven: {Ca3.09}[Cr1.36Al0.35Ti0.11Fe 0.06V0.02Mg0.01]

Σ1.90(Si2.86Al0.15)Σ3.00O12; Uv68Grs17Sch5Adr3 (Table 3.1.0.). BSE images showed no sign of zoning features or subtle contrasts in the crystals, however, distinct birefringence is observed

(Figure 3.1.3.1. and 3.1.3.2.). Uvarovite composition ranges from Uv58 to Uv68 while grossular proportionally decreases from Grs27 to Grs17. The Cr2O3 wt. % ranges from 17.37 to 19.70 %,

similar to that of SAR-2, but PPL XPL larger than SAR-1. Analyzed

points closer to the center of the

crystals represented lower Uv

composition compared to points a SKR-1 b near the rim. The {X} site is REFL BSE completely filled with Ca2+ and

minor traces of Mn2+ and in the

[Y] site, across point six to

seven displays the largest c d 500 µm Figure 3.1.3.1. SKR-1 illustrating a. deep green colour in increase in Cr3+ cations from PPL b. XPL image displaying distinct birefringence with faint extinction positions c. Reflected light image with 1.250 to 1.357 apfu and prominent inclusions in the crystal and d. BSE image with EMPA points labeled are given in Appendix A (Table simultaneously a corresponding A1.3). The scale bar in d. represents 500 µm. decrease in Al3+ from 0.484 to

0.352 apfu occurs. Another major difference between SKR-1 from the other two Russian samples is that apfu values of Fe3+ are lower than that of Ti4+ across all seven points. In addition, the presence of minor Al3+ cations in the (Z) site along with the Si atoms in conjunction with Ti4+ atoms in the [Y] site results in the elevated composition of Schorlomite-Al.

SKR-1 a b

PPL XPL c d

REFL 500 µm BSE

Table 3.1.3. EMPA of three representative phases of uvarovite in SKR-1 from Saranovskii, Russia Oxide (wt. %) Phase-1 Phase-2 Avg. (1-6) pt. 7 SiO2 33.93 32.73 TiO2 1.81 1.65 Al2O3 6.19 4.87

Cr2O3 17.83 19.70

V2O3 0.35 0.29

Fe2O3 / calc 0.99 0.93 MnO 0.05 0.05 MgO 0.05 0.04 CaO 33.73 33.13 Σ (calc) 94.94 93.38 Recalculated (wt. %) final Fe2O3 0.99 0.93 final MnO 0.06 0.05 Σ 94.94 93.38 Cations for 12 O atoms Ca 3.077 3.093 Mn2+ 0.004 0.004 ΣX 3.081 3.096 Cr 1.200 1.357 Al 0.509 0.352 Fe3+ 0.064 0.061 Ti 0.116 0.108 Mg 0.006 0.005 V 0.024 0.020 ΣY 1.919 1.904 Si 2.888 2.852 Al 0.112 0.148 ΣZ 3.000 3.000 EMPA X sof 1.027 1.032 EMPA Y sof Cr 0.839 0.867 EMPA Z sof 0.997 0.996 F(000) 144 145 End-Member mole % Uvarovite 60 68 Grossular 25 17 Andradite 3 3 Schorlomite-Al 5 5 Goldmanite 1 1 Remainder 5 4 Σ 100 100 Quality Index Poor Poor Analysis of SKR-1 with seven analyzed points is given in Appendix A.

3.5 a {X} site 3.0

2.5 , Mg) 2+ 2.0 Phase 1 Phase 2

1.5 (Ca, Mn (Ca,

1.0 apfu Ca 0.5 Mn2+

0.0 1 2 3 4 5 6 7 1.6 b [Y] site

1.4 Cr 1.2 Cr

, Mg, V) , Mg, Fe3+

3+ 1.0 Al 0.8 V Ti 0.6 Al Mg

(Cr, Al, Ti, Fe Ti, Al, (Cr, 0.4

apfu 0.2

0.0 1 2 3 4 5 6 7 3.5 c (Z) site 3.0

2.5

2.0

(Si, Al) (Si, Si

1.5 Al apfu

1.0

0.5

0.0 1 2 3 4 5 6 7 Points

3.1.4 STZ-1

Based on the EMPA results, STZ-1 constitutes two different phases between five crystals containing 14 analyzed points (Figure 3.1.4.1 to 3.1.4.5). Each phase of STZ-1 is comprised of a

2+ Uv-Grs-Adr solid-solution (Table 3.1.6.1) and is as follows, Phase-1: {Ca2.94Mn 0.03Mg0.01}Σ2.98

3+ 2+ [Al1.06Fe 0.50Cr0.44Ti0.02]Σ2.01(Si2.99Al0.01)Σ3.00O12; Uv22Grs51Adr24 and Phase-2: {Ca2.96Mn 0.02

3+ Mg0.01}Σ2.99 [Cr0.87Al0.69Fe 0.43Ti0.01Si0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12; Uv43 Grs34Adr21. From points

1 to 14, the maximum difference in uvarovite composition is 39 % ranging from Uv12 to Uv51.

The BSE image of STZ-1 reveals variations in contrasts with differences in composition where elemental maps of Al shows the most pronounced variations, Cr displaying subtle changes, while no difference is observed in Fe (Figure 3.1.4.1).

Phase-1 represents an average of points one to ten, where Uv composition gradually increases but stays constant at Uv21 from point three to five (Figure 3.1.4.3). Additionally, points three to four (Appendix A; Table A1.4) show an unusual change between the decreasing Al3+ from 1.123 to 0.988 apfu, and inversely increasing Fe3+ from 0.485 to 0.588 apfu. While Cr3+ atoms exhibits a very minor increase (< 0.008 apfu), maintaining a linear trend (Figure 3.1.4.3b).

This results in a 9 % decrease from Grs55 to Grs48 while Adr increases 8 % from Adr21 to Adr29.

The opposite effect can be observed from point four to five where increasing Al3+ (0.988 to

1.110 apfu) and decreasing Fe3+ (0.588 to 0.454 apfu), whereas Cr3+ shows a slight increase (<

0.005 apfu). This fluctuation in [Y] site cations results in changes to Grs and Adr compositions.

Similarly, points 10 to 11 show a drastic increase in Al3+ atoms from 0.954 to 0.743 apfu with a gradual decrease in Fe3+. Meanwhile, a substantial increase in Cr3+ atoms from 0.534 to 0.736 apfu is evident (Figure 3.1.4.3b). This drastic rise in Cr3+ apfu is represented as the start of phase-2 and signifies equal Uv and Grs proportions of 37 %.

STZ-1

a REFL b BSE c Al

100 µm

d Cr e Fe

STZ-1 500 µm

a PPL e XPL i REFL

b f j

c g k

d h l Figure 3.1.4.2. STZ-1 displaying a. to d. deep green colour in PPL e. to h. XPL images show low birefringence i. to l. Reflected light image with inclusions and EMPA points labeled are given in Appendix A (Table A1.4). The scale bar in e. represents 500 µm.

Table 3.1.4. EMPA of two phases of uvarovite in STZ-1 from Zermatt, Switzerland Oxide (wt. %) Phase-1 Phase-2 Avg. (1-10) Avg. (11-14) SiO2 37.45 36.93 TiO2 0.29 0.24 Al2O3 11.29 7.36 Cr2O3 6.91 13.49 Fe2O3 / calc 8.31 7.00 MnO 0.42 0.31 MgO 0.13 0.08 CaO 34.33 34.07 Σ (calc) 99.14 99.46 Recalculated (wt. %) final Fe2O3 8.31 7.00 final MnO 0.42 0.31 Σ 99.14 99.47 Cations for 12 O atoms Ca 2.942 2.962 Mn2+ 0.029 0.021 Mg 0.014 0.008 ΣX 2.984 2.991 Al 1.055 0.694 Fe3+ 0.500 0.427 Cr 0.438 0.866 Ti 0.018 0.014 Mg 0.002 0.002 Si 0.004 0.006 ΣY 2.016 2.009 Si 2.991 2.991 Al 0.009 0.009 ΣZ 3.000 3.000 EMPA X sof 0.995 0.998 EMPA Y sof Cr 0.785 0.861 EMPA Z sof 1.000 1.000 F(000) 139 143 End-Member mole % Uvarovite 22 43 Grossular 51 34 Andradite 24 21 Spessartine 1 1 Remainder 1 1 Σ 100 100 Quality Index Excellent Excellent Analysis of STZ-1 with 14 analyzed points are given in Appendix A (Table A1.3).

3.5 a {X} site 3.0

2.5

, Mg) 2.0 2+ Phase 1 Phase 2 1.5 (Ca, Mn (Ca, 1.0 Ca

apfu Mn2+ 0.5 Mg

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

1.4

b [Y] site 1.2

, Ti ) Ti , Cr Al 3+ 1.0 Fe3+ Al 0.8 Si Ti Fe3+ 0.6 Mg

0.4 (Cr, Al, M,g, Si, Fe (Cr, Cr

apfu 0.2

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

3.5 c (Z) site 3.0

2.5

2.0 Si (Si, Al) (Si, 1.5 Al apfu 1.0

0.5

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Points

3.1.5 JTC-1

EMPA data determined that JTC-1 possess two representative phases of contrasting chemical compositions derived from 25 analyzed points between seven crystals (Figure 3.1.5.1 to 3.1.5.3) and comprise of a Uv-Adr-Grs solid solution series (Table 3.1.5.1). The chemical

3+ compositions, Phase-1: {Ca2.98}[Fe 1.76Cr0.17Al0.05Ti0.02Si0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12; Uv9Adr88

2+ Grs2 and Phase-2: {Ca2.99Mg0.01Mn 0.01} BSEa a 3+ Σ3.01[Fe 1.29Cr0.61Al0.06Ti0.02Si0.01Mg0.01]

Σ2.00(Si2.99Al0.01)Σ3.00O12; Uv30Adr64Grs3

(Table 3.1.0.) are an average of points 1 to 19 in Phase-1 while Phase-2 comprises of points 20 to 25. The individual chemical analyses revealed the dominant JTC-1 REFL b c end-member to be andradite varying from

Adr59 to Adr93, with significant uvarovite ranging from Uv1 to Uv36 (Appendix A:

Table A1.5.). Cr2O3 wt. % increases from 0.28 to 10.82 % while Fe2O3 50 µm decreases from 30.06 to 18.88 % along Figure 3.1.5.1 a. BSE image of JTC-1 displaying distinct contrast in zoning boundaries. JTC-1 points 1 to 25. This inverse relationship crystals b. and c. with EMPA points labeled are given in Appendix A (Table A1.5). The scale bar in between Cr3+ and Fe3+ atoms affect the a. and b. both represents 50 µm. variations in apfu within the [Y] site significantly. The maximum variation in Fe3+ apfu is 0.714 from 1.185 to 1.899, resulting in high Adr composition. Subsequently, Cr3+ leads afterwards, with a difference of 0.695 apfu from 0.019 to 0.714 apfu. The largest increase in Cr2O3 occurs

between points 19 (Figure 3.1.5.2a) and 20 (Figure 3.1.5.2d) with a difference of 2.09 % from

5.44 to 7.53 wt. % and inversely the largest decrease in Al2O3 also occurs at the same points with

2.63 % from 24.90 to 22.27 wt. %. Increasing Uv generally increases from the rim to the core of the crystals as seen in Figure 3.1.5.2a to 3.1.5.2d. A similar effect on their corresponding cations

3+ 3+ within the [Y] site, between Cr and Fe atoms and signifies the largest jump from Uv18 to Uv25 compared to any other point in JTC-1. These points divide the two distinct phases in JTC-1

(Figure 3.1.5.5c.). Phase-1 is an average of points 1 to 19 with a composition of Uv9 and phase-

2 is comprised of points 20 to 25 with Uv30.

JTC-1 BSE Inc

a b c d

Inc

100 µm

a PPL b XPL

JTC-1 c REFL d BSE

100 µm Figure 3.1.5.3. JTC-1 from Jacksonville, California illustrating a. deep green colour in PPL b. XPL image displaying distinct birefringence c. Reflected light image with minor inclusions and fractures and d. BSE image shows subtle variations in contrast. EMPA points labeled are given in Appendix A (Table A1.5). The scale bar in d. represents 100 µm.

Table 3.1.5. EMPA of two different phases of uvarovite-andradite in JTC-1 from Jacksonville, Tuolumne County, California Oxide (wt. %) Phase-1 Phase-2 Avg. (1-19) Avg. (20-25)

SiO2 35.63 35.62 TiO2 0.34 0.36 Al2O3 0.62 0.75 Cr2O3 2.58 9.13 V2O3 0.00 0.01 Fe2O3 / calc 27.79 20.39 MnO 0.05 0.08 MgO 0.04 0.08 CaO 33.10 33.27 Σ (calc) 100.16 99.69 Recalculated (wt. %)

final Fe2O3 27.79 20.39 final MnO 0.05 0.08 Σ 100.16 99.69 Cations for 12 O atoms

Ca 2.982 2.996 Mg 0.003 0.004 Mn2+ 0.004 0.005 Na 0.000 0.000 ΣX 2.989 3.005 Fe3+ 1.758 1.289 Cr 0.172 0.607 Al 0.047 0.064 Si 0.011 0.005 Ti 0.022 0.023 Mg 0.002 0.007 V 0.000 0.001 ΣY 2.011 1.995 Si 2.985 2.989 Al 0.014 0.011 Fe3+ 0.000 0.000 ΣZ 3.000 3.000 EMPA X sof 0.996 1.002 EMPA Y sof Cr 1.064 1.033 EMPA Z sof 1.000 1.000 F(000) 153 152 End-Member mole %

Uvarovite 9 30 Andradite 88 64 Grossular 2 3 Remainder 1 1 Σ 100 100 Quality Index Excellent Excellent Analysis of JTC-1 with 25 analyzed points are given in Appendix A (Table A1.5).

3.5 {X} site 3.0

2.5 Phase 1 Phase 2 2.0 a 1.5 (Ca, Mg, (Ca, Mn ) 1.0 apfu Ca 0.5 Mn2+ Mg 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 2.0 [Y] site 1.8

1.6 Cr 1.4 Fe3+ Fe3+ 1.2 Al

, Al, Si, Ti, V ) V Ti, Al, Si, , 1.0 Si 3+ b 0.8 Ti Mg 0.6 Cr V 0.4 (Cr, Mg, Fe (Cr, 0.2 apfu 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 3.5 (Z) site 3.0

2.5

2.0 Si c (Si, Al) (Si, 1.5 Al apfu 1.0

0.5

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Points Figure 3.1.5.4. Apfu distribution from EMPA results for 25 analyzed points of JTC-1. a. {X} site partitioning with Ca2+ as the dominant cation. b. [Y] site displaying a gradual increase in Cr3+ and decreasing Fe3+. c. (Z) site show Si4+ as the dominant cation.

3.1.6 FIN-1

EMPA determined four chemically distinct phases of FIN-1 exist between 15 analyzed points from two crystals and comprise of an Uv-Grs solid solution (Table 3.1.6.1.). A detailed analysis of EMPA data for FIN-1 is given in Appendix A (Table A1.6.) with apfu distribution on corresponding sites in Figure 3.1.6.3. Compositions of each phase are as follows,

2+ 3+ Phase-1: {Ca2.92Mn 0.05Mg0.04}Σ3.00[Al0.98Cr0.92Fe 0.03Ti0.03Mg0.03V0.01]Σ2.00(Si2.98Al0.02)Σ3.00O12;

2+ 3+ Uv46Grs46Mmt3, Phase-2: {Ca2.92Mn 0.04Mg0.04}Σ3.00[Cr1.12Al0.79Fe 0.03Ti0.02V0.01Mg0.01Si0.01]

2+ 3+ Σ2.00(Si3.00)Σ3.00O12; Uv56Grs37Adr2, Phase-3: {Ca2.93Mn 0.03Mg0.3}Σ2.99 [Cr1.35Al0.58Fe 0.03Ti0.01

2+ V0.01Mg0.01Si0.01]Σ2.01(Si2.99Al0.01)Σ3.00 O12; Uv68Grs27Adr1; and Phase-4: {Ca2.88Mn 0.04Mg0.4}Σ2.96

3+ [Cr1.43Al0.54Si0.04Fe 0.03Ti0.01]Σ2.04(Si3.00)Σ3.00O12; Uv71Grs24Sps1 (Table 3.1.0.).

The maximum uvarovite end-member difference is 27% increasing from Uv46 to Uv73, whereas grossular decreases from Grs46 to Grs23 with a difference of 23%. Points one and two represent phases-1 and 2, respectively, while points three to seven represents phase-3 and points

8 to 15 comprise of phase-4. Cr3+ apfu increases from 0.922 to 1.466; in contrast, Al3+ decreases from 0.982 to 0.510 apfu. Point one represents the only point where Al3+ is greater than Cr3+.

Minor subtle variations occur for Ca2+ in the {X} site with ≤ 0.100 apfu (Figure 3.1.6.3a) whereas the Si4+ cation predominantly occurs across all analyzed points displaying a flat linear line (Figure 3.1.6.3c). BSE image (Figure 3.1.6.1a) clearly show distinct contacts between the garnet host and the coexisting garnet enclosing points one and two in the darker area while the remainder of the points are located in lighter areas. These points are consistent with the lower

F(000) values of 139 and 141 for points one and two, respectively, indicate darker areas while higher total number of electrons are situated in lighter areas. In addition, the appearance of morimotoite-Mg occurs from Mmr3 to Mmr1 at points one and two and emerges again at 1% at

57 point’s three and eight whereas, trace amounts of Goldmanite only occurs within the lighter areas

(Figure 3.1.6.1d). Sps and Py are consistently present all throughout the analyzed points also in minimal amounts. Calcite and chalcopyrite have been determined by EDS analysis and are labeled in Figures 3.1.6.1d and 3.1.6.2d. Higher Uv composition points are mostly located in the second crystal of FIN-1 and display no compositional zoning or a second coexisting garnet inclusion as in Figure 3.1.6.1d.

a PPL b XPL

FIN-1 c REFL d BSE Inc

Ccp Cal 80 µm

a REFL b BSE Cal

Inc

Ccp 100 µm FIN-1 Figure 3.1.6.2. FIN-1 illustrating a. Reflected light image with prominent inclusions and fractures in the crystal and d. BSE image shows subtle variations in contrast with chalcopyrite and calcite. EMPA analyses obtained from the points labeled are given Appendix A (Table 1.6). The scale bar in d. represents 100 µm.

Table 3.1.6. EMPA of four distinct phases of Uv in FIN-1 from Outokumpu, Finland Oxide (wt. %) Phase-1 Phase-2 Phase-3 Phase-4 pt. 1 pt. 2 Avg. (3-8) Avg. (9-15) SiO2 37.06 37.04 36.52 37.13 TiO2 0.50 0.33 0.16 0.14 Al2O3 10.33 8.26 6.00 5.67 Cr2O3 14.41 17.45 20.83 22.16 V2O3 0.07 0.15 0.16 0.00 Fe2O3 / calc 0.52 0.51 0.52 0.47 MnO 0.69 0.55 0.47 0.50 MgO 0.56 0.46 0.32 0.34 CaO 33.63 33.51 33.26 33.02 Total (calc) 97.77 98.26 98.23 99.42 Recalculated (wt. %)

final Fe2O3 0.52 0.51 0.52 0.47 final MnO 0.69 0.55 0.47 0.50 Σ(calc) 97.78 98.26 98.23 99.42 Cations for 12 O atoms

Ca 2.915 2.920 2.933 2.885 Mn2+ 0.047 0.038 0.033 0.035 Mg 0.038 0.044 0.028 0.040 ΣX 3.000 3.001 2.993 2.960 Cr 0.922 1.122 1.355 1.429 Al 0.982 0.792 0.575 0.543 Fe3+ 0.031 0.031 0.032 0.029 Ti 0.031 0.020 0.010 0.009 Mg 0.030 0.012 0.012 0.001 V 0.005 0.010 0.011 0.000 Si 0.000 0.012 0.012 0.030 ΣY 2.000 1.999 2.007 2.040 Si 2.998 3.000 2.994 2.998 Al 0.002 0.000 0.006 0.002 ΣZ 3.000 3.000 3.000 3.000 EMPA X sof 0.999 0.998 0.997 0.984 EMPA Y sof Cr 0.767 0.813 0.867 0.890 EMPA Z sof 1.000 1.000 1.000 1.000 F(000) 139 141 143 144 End-Member mole %

Uvarovite 46 56 68 71 Grossular 46 37 27 24 Morimotoite-Mg 3 1 0 0 Andradite 2 2 1 0 Spessartine 2 1 1 1 Pyrope 1 1 1 1 Goldmanite 0 0 1 0 Remainder 0 1 1 1 Σ 100 100 100 100 Quality Index Superior Fair Exc Fair Analysis of FIN-1 with 15 analyzed points are given in Appendix A (Table A1.5).

3.5 a {X} site 3.0

2.5 , Mg) 2+ 2.0 Phase 3 Phase 4 Phase 2 1.5 Phase 1 (Ca, Mn (Ca, 1.0 apfu Ca 0.5 Mn2+ Mg 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1.8 b [Y] site 1.6

1.4 Cr 1.2 Cr Fe3+ Al

, Ti, Mg, V, Si) V, Mg, Ti, , 1.0 Si 3+ 0.8 Al Ti Mg 0.6 V

(Cr, Al, Fe (Cr, 0.4

apfu 0.2

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

3.5 c (Z) site 3.0

2.5

2.0 Si (Si, Al) (Si, 1.5 Al apfu 1.0

0.5

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Points Figure 3.1.6.3. Apfu distribution from EMPA results for 15 analyzed points of FIN-1. a {X} site with Ca2+ as the dominant cation. b. [Y] site displaying a significant increase in Cr3+ from points 1 and 2 leading by a gradual increase in Cr3+ and inversely decreasing Al3+. c. (Z) site displaying Si4+ as the dominant cation.

3.1.7 Comparison between the six uvarovites garnets

All six birefringent uvarovite samples have a solid solution series with Grs and/or Adr containing variable Uv composition. Five out of the six studied samples contains at least one crystal that features additional anisotropic properties such as zoning and/or subtle variations in contrasts representative of coexisting phases displaying different chemical compositions. The uvarovites in this study have Cr2O3 wt. % varying from 0.28 % in JTC-1 to 22.73 % in FIN-1.

nd JTC-1 contains the smallest Uv end-member composition from Uv1 to Uv36, but possess the 2 largest range of 35 % between all six samples. In addition, JTC-1 contains the largest Adr composition between all studied samples varying from Adr59 to Adr93 and contains the least amount of grossular up to Grs4. Moreover BSE images (Figure 3.1.5.3) of JTC-1 analyzed points show no sign of zoning or differences in contrast but EMPA reveals major compositional differences. STZ-1 leads with a maximum difference in uvarovite composition of 39 % from

Uv12 to Uv51, and is the only sample to contain significant proportions of all three Uv, Grs, and

Adr end-members. FIN-1 consists of the highest Uv composition at Uv73 while SAR-1, SAR-2, and SKR-1 have smaller variations in Uv end-member and comprises of phases of similar Uv proportions, which is expected since they are all within the general locality of the Ural

Mountains.

SAR-1 and SAR-2 have distinct chemical compositions despite being from the same locality. Optical Microscopy and BSE images show that SAR-1 and SAR-2 are chemically heterogeneous both exhibiting a black chromite core with bands of pronounced zoning on several crystals (Figures 3.1.1.1a, 3.1.1.2d, and 3.1.1.3d). Additionally, SKR-1 exhibits a bow-tie structure (Figure 2.2.1), which contains the highest Uv composition from the Ural Mountains compared to SAR-1 and SAR-2. One JTC-1 crystal displays zoning while the remaining six

62 crystals from California appear to be homogenous yet EMPA determined two separate chemical phases. Noticeable light and dark areas of coexisting garnet compositions are prominent in STZ-

1 and FIN-1 (Figure 3.1.4.1b and 3.1.6.1d).

For all Uv samples partitioning in the dodecahedral {X} site is dominantly filled by the

Ca2+ cation, with very minor amounts of Mn2+ and Mg2+ occupying the remaining vacancies.

The greatest variability of cation partitioning occurs within the octahedral [Y] site. As seen from the analyzed points of SAR-1, SAR-2, SKR-1, and FIN-1 in Appendix A, there are large variations between Cr3+ and Al3+ apfu, with the remaining occupancy filled with trace amounts of Fe3+, Ti, V3+, Mg and Si. However, in STZ-1 there are considerable amounts of Fe3+ in addition to Cr3+ and Al3+ apfu, resulting in a solid solution series between all three ugrandite end- members with relatively significant proportions of Adr composition.

JTC-1 primarily comprises an exchange between large concentration of Fe3+ and Cr3+ in the [Y] site indicating a solid solution series between Uv and Adr with little Grs component.

Cation partitioning indicates that Si4+ nearly fully occupies the tetrahedral (Z) site with variable trace amounts of Al3+ filling the remaining vacancies in all Uv samples. The appearance of other garnet species outside the six main end-members indicates the complex nature of cation partitioning to yield such a diverse set of conditions to be met for formation to occur.

3+ Goldmanite (Ca3V2Si3O12) occurs when V cations occupy the [Y] site, which is consistently present up to 0.034 apfu across all analyzed points in SAR-2 and SKR-1 but is not observed in the remaining Uv specimens. When excess Ti4+ and Mg cations occupy the remaining vacant octahedral sites, morimotoite-Mg (Ca3TiMgSi3O12) can form, and is evident in all analyzed points of SAR-2, SKR-1, as well as phase 1 and 2 of FIN-1. All samples have very minimal

63 proportions of schorlomite-Al (Ca3Ti2SiAl2O12) with the largest reported in SKR-1 to have Sch5, whereas SAR-1 contains no schorlomite content.

Many crystals in the study from each locality did not exhibit any zoning or contrasts in BSE images. However, the presence of birefringence in each sample is well defined and indicates a strong relationship between chemical composition and the crystal structure. The zoning and sharp differences in contrasts observed in these samples comprise compositions of different Uv end-members ranging from Cr-rich and Cr-poor varieties. Overall, samples from the same locality generally have similar composition with fluctuations in cation apfu site partitioning causing the appearance of minor elusive end-members. All other samples exhibit similar Uv proportions with variations in end-member solid solutions between other garnet species, indicating the complex nature of uvarovite garnet. Figure 3.1.7 illustrates a ternary diagram of each individual EMPA analyzed point in this study represented by the coloured circles compared to the literature Uv data samples. SAR-1, SAR-2, SKR-1, and FIN-1 represents Uv-Grs solid solutions whereas STZ-1 contain considerable proportions of each ugrandite end-member and are located near the middle of the diagram. Lastly, JTC-1 represents an Uv-Adr solid solution and is located closer to the Adr end-member. The wide distribution between ugrandite end- members indicates the chemical compositional complexity of each Uv garnet in this study.

Ca3Cr2Si3O12 Uvarovite SAR-1 SAR-2 SKR-1 STZ-1

JTC-1 FIN-1 Literature 30

Grossular 30 60 Andradite Ca3Al2Si3O12 Ca3Cr2Si3O12

Figure 3.1.7. Ugrandite ternary diagram between Uv, Grs, and Adr garnets displaying a wide range in end-member compositions. Coloured outlined circles represent each analyzed point in this study whereas solid coloured circles represent distinct EMPA phases. Black white circles are Uv samples from literature data obtained from Spiridonov et al. (2006), Taran et al. (1994), Knorring (1986), Moroz et al. (2009), Pal and Das (2010), Wildner and Andrut (2001), Arai and Akizawa (2014), and Proenza et al. (1999).

3.1.8 Comparison with Literature

All Uv samples in this study represent a solid solution series between Uv, Grs, and Adr end-member species and are illustrated on a ternary diagram in Figure 3.1.7. SAR-1, SAR-2, and SKR-1 are compared to literature data from Andrut and Wildner (2001) (six natural birefringent uvarovites), their samples Sar-desy, Sar-kl2, Sar-899, and Sar-w2 obtained from the

Saranov locality, Ska-1 from Saranka, and Ves-2 from Veselovsk, Ural Mountains, Russia. In addition, Spiridonov et al. (2006) five Uv samples, Sawada (1999), Bocchio et al. (2004), and

Moroz et al. (2009) eight ugrandite garnets (m1-2a, m1-3, m1-3a, m1-3b, m1-5, m1-2, m1-2b, and m1-5a) all from the Ural Mountains region of Russia are also used for comparison (Figure

3.1.8.1.). A total of 21 EMPA literature data points are compared to the 18 analyzed points of

SAR-1, SAR-2, and SKR-1 (Table 3.1.8.1).

The {X} site displays Ca2+ as the dominant cation across the 18 points and matches with the literature data (Figure 3.1.8.1a). Most of SAR-1 data points containing Ca2+ apfu overlap the literature values of Moroz et al. (2009), while SAR-2 and SKR-1 have slightly elevated Ca2+

(>3.00 apfu). Similarly, in Figure 3.1.8.1c the (Z) site is dominated by Si4+ cations with overlapping SAR-1 Si atoms with Moroz et al. (2009). However, the Si4+ content gradually decreases along the analyzed points into SAR-2 and SKR-1 with slightly elevated Al3+. The [Y] site (Figure 3.1.8.1b) contains the most substitution and variation compared to the {X} and (Z) sites. SAR-1 displays a gradual increase in Cr3+ from 0.918 apfu at point one to 1.357 apfu in

SKR-1 at point 18 with a maximum difference of 0.439 apfu. Spiridonov et al. (2006) Uv samples from point 17 to point 21 show similar values to that of SAR-1, SAR-2, and SKR-1, and also represent the highest Cr3+ apfu from the Urals, Russia of 1.759. Overall, the analyzed points

66 of Cr3+ from SAR-1, SAR-2, and SKR-1 are positioned between these values and are consistent with the literature data of Cr3+ apfu of Uv obtained from the Ural Mountains of Russia.

In addition to Cr3+, there is an inverse relationship observed with Al3+ cations decreasing across the analyzed points. At point one Al3+ ranges from 1.161 in SAR-1 to 0.352 apfu in SKR-

1 at point 18, with a difference of 0.809 apfu. Moreover, the maximum difference in Al3+ from previous studies is 0.502 apfu from Moroz et al. (2009) at point two of 0.968 to Bocchio et al.

(2010) at point 16 with 0.466 apfu. However, SAR-1 contains the highest Al3+ apfu from points one to four and deviate from the highest literature data by ~0.190 apfu. In SAR-1, from point four to five Cr3+ surpasses Al3+ in apfu, occupying a larger occupancy in the [Y] site. This is not observed in the literature data, instead a gradual increase in Cr3+ along with a decrease in Al3+ consisting of approximately equal proportions is shown by overlapping hollow shapes in both

Moroz et al. (2009) points seven, eight, and in Andrut and Wildner (2001) point nine (Figure

3.1.8.1b). Literature data indicated no information of any schorlomite or morimotoite compositions found near or associated with the Uv from the Urals. In addition, most literature

EMPA results did not test for the presence of V2O3, with the exception of Spiridonov et al.

(2006) study, but they also did not indicate any information on the presence of goldmanite in their samples.

Table 3.1.8. Locality and chemical compositions of Uv-Grs solid solutions obtained from literature data for comparison. Point number indicates the position of samples on the {X], [Y], and (Z) sites in Figures 3.1.8.1 to 3.1.8.3. SAR-1, SAR-2, and SKR-1 are compared to Urals literature data in Figure 3.1.8.1. Figure 3.1.8.2. is representative of JTC-1 and is compared to Novak and Gibbs (1971) Uv from California. FIN-1 is correlated to Finland literature data in Figure 3.1.8.3. All samples indicated were calculated using the Locock (2008) Excel spreadsheet with the exception of Sawada (1997) and Novak and Gibbs (1971) Pt. Sample Locality Author Composition 3+ 1 m1-3b Southern Ural, Russia Moroz et al. (2009) {Ca2.97Mg0.01}Σ2.98[Cr0.74Fe 0.66Al0.58Ti0.03]Σ2.01(Si2.84Al0.16)Σ3.00O12 2+ 3+ 2+ 2 m1-2 Southern Ural, Russia Moroz et al. (2009) {Ca2.96Mg0.02Fe 0.02}Σ3.00[Cr0.84Al0.97Fe 0.13Ti0.04Fe 0.02]Σ2.00(Si2.99Al0.01)Σ3.00O12 2+ 3+ 2+ 3 m1-2a Southern Ural, Russia Moroz et al. (2009) {Ca2.96Mg0.02Fe 0.02}Σ3.00[Cr0.85Al0.95Fe 0.14Ti0.04Fe 0.02]Σ2.00(Si2.99Al0.01)Σ3.00O12 2+ 3+ 4 m1-2b Southern Ural, Russia Moroz et al. (2009) {Ca2.95Mg0.02Fe 0.02Na0.01}Σ3.00[Cr0.85Al0.94Fe 0.18Ti0.03]Σ2.00(Si2.97Al0.03)Σ3.00O12 2+ 2+ 3+ 2+ 5 m1-5 Southern Ural, Russia Moroz et al. (2009) {Ca2.93Fe 0.03Mg0.02Mn 0.01Na0.01}Σ3.00[Cr0.87Al0.96Fe 0.12Ti0.04Fe 0.02]Σ2.00(Si2.99Al0.01)Σ3.00O12 2+ 3+ 2+ 6 m1-5a Southern Ural, Russia Moroz et al. (2009) {Ca2.93Fe 0.04Mg0.02}Σ2.99[Cr0.89Al0.96Fe 0.08Ti0.04Fe 0.04]Σ2.00(Si3.00)O12 2+ 3+ 2+ 7 m1-3a Southern Ural, Russia Moroz et al. (2009) {Ca2.93Fe 0.05Mg0.02}Σ2.99[Cr0.90Al0.93Fe 0.10Ti0.04Fe 0.03]Σ2.00(Si3.00)O12 2+ 3+ 2+ 8 m1-3 Southern Ural, Russia Moroz et al. (2009) {Ca2.95Mg0.03Fe 0.02}Σ3.00[Cr0.92Al0.90Fe 0.11Ti0.05Fe 0.03]Σ2.00(Si2.90Al0.01)Σ3.00O12 2+ 3+ 9 Ska-1 Saranka, Ural, Russia Andrut & Wildner (2001) {Ca2.96Mn 0.02}Σ2.98[Cr0.96Al0.97Fe 0.07Ti0.02Si0.01]Σ2.03(Si3.00)O12 3+ 10 Ves-2 Veselovsk, Ural, Russia Andrut & Wildner (2001) {Ca2.97Mg0.01}Σ2.97[Cr1.32Al0.63Ti0.06Si0.02Fe 0.01]Σ2.03(Si3.00)O12 3+ 11 Sar-w2 Saranov, Ural, Russia Andrut & Wildner (2001) {Ca2.96}[Cr1.36Al0.61Ti0.04Si0.02Fe 0.01]Σ2.04(Si3.00)O12 3+ 12 Sar-899 Saranov, Ural, Russia Andrut & Wildner (2001) {Ca2.98}[Cr1.39Al0.58Ti0.04Si0.01Fe 0.01]Σ2.02(Si3.00)O12 3+ 13 Sar-kl2 Saranov, Ural, Russia Andrut & Wildner (2001) {Ca2.99}[Cr1.39Al0.55Ti0.07Fe 0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12 3+ 14 Sar-desy Saranov, Ural, Russia Andrut & Wildner (2001) {Ca2.98}[Cr1.42Al0.51Ti0.08Fe 0.01]Σ2.01(Si3.00)O12 3+ 15 CCG Ural Mountains, Russia Sawada (1997, 1999) {Ca3.00}[Cr1.10Al0.80Ti0.06Fe 0.03]Σ1.99(Si3.00)O12 2+ 16 UV Sarany, Ural, Russia Bocchio et al. (2010) {Ca2.99Mg0.01}Σ3.00[Cr1.42Al0.47Ti0.07Fe 0.03V0.01]Σ2.03(Si2.99Al0.01)Σ3.00O12 3+ 17 1 Sarany, Ural, Russia Spiridonov et al. (2006) {Ca3.05}[Cr1.76Ti0.10Fe 0.04V0.02Al0.02Mg0.01]Σ1.94(Si2.91Al0.09)Σ3.00O12 3+ 18 2 Sarany, Ural, Russia Spiridonov et al. (2006) {Ca2.99}[Cr1.60Al0.34Ti0.04Fe 0.02]Σ2.01(Si3.00)O12 3+ 19 3 Sarany, Ural, Russia Spiridonov et al. (2006) {Ca2.98}[Cr1.46Al0.47Ti0.05Fe 0.03V0.01]Σ2.02(Si2.98Al0.02)Σ3.00O12 3+ 20 4 Sarany, Ural, Russia Spiridonov et al. (2006) {Ca2.98}[Cr1.22Al0.70Fe 0.08Ti0.01]Σ2.02(Si2.97Al0.03)Σ3.00O12 3+ 21 5 Sarany, Ural, Russia Spiridonov et al. (2006) {Ca3.00Mn0.01}Σ3.01[Cr1.20Al0.76Fe 0.02Ti0.02]Σ2.00(Si2.99Al0.01)Σ3.00O12 2+ 3+ 26 Uv Washington, California Novak & Gibbs (1971) {Ca2.99Mn 0.01}Σ3.00[Cr1.73Al0.21Fe 0.05Ti0.01]Σ1.98(Si3.00)O12 2+ 3+ 7 14c Outokumpu, Finland Knorring et al. (1986) {Ca2.81Mg0.07Mn 0.06}Σ2.94[Cr1.02Al0.90Fe 0.10V0.03Ti0.01]Σ2.06(Si2.99Al0.01)Σ3.00O12 2+ 3+ 11 Uv-a Outokumpu, Finland Amthauer (1976) {Ca2.99Mg0.08Mn 0.03}Σ2.99[Cr1.05Al0.88Fe 0.07Ti0.01]Σ2.01(Si3.00)O12 2+ 3+ 15 7c Outokumpu, Finland Knorring et al. (1986) {Ca2.88Mg0.07Mn 0.05}Σ3.00[Cr1.16Al0.78Fe 0.04V0.02Ti0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12 2+ 3+ 26 Out-Kh Outokumpu, Finland Langer et al. (2004) {Ca2.99Mg0.05Mn 0.04}Σ2.99[Cr1.05Al0.88Fe 0.07Ti0.01]Σ2.01(Si3.00)O12 2+ 2+ 30 Uvarovite Outokumpu, Finland Diella et al. (2004) {Ca2.89Mg0.05Mn 0.04Fe 0.03}Σ3.01[Cr1.24Al0.75Ti0.02]Σ2.01(Si2.98Al0.02)Σ3.00O12 3+ 35 Uvarovite Outokumpu, Finland Taran et al. (1994) {Ca3.04}[Cr1.31Al0.62Ti0.02Fe 0.01]Σ1.96(Si2.87Al0.14)Σ3.00O12 2+ 3+ 36 6 Outokumpu, Finland Knorring et al. (1986) {Ca2.92Mn 0.04Mg0.02}Σ2.98[Cr1.33Al0.61Fe 0.05V0.03Ti0.01]Σ2.03(Si2.97Al0.03)Σ3.00O12 2+ 3+ 45 12r Outokumpu, Finland Knorring et al. (1986) {Ca2.91Mn 0.03Mg0.03}Σ2.97[Cr1.52Al0.42Fe 0.04V0.04Ti0.01]Σ2.03(Si2.99Al0.01)Σ3.00O12 3+ 50 - Sysmä, Finland Menzer (1928) {Ca3.00}[Cr1.79Al0.19Fe 0.02]Σ2.00(Si3.00)O12

JTC-1 is compared to Novak and Gibbs (1971) uvarovite sample from Washington,

2+ Nevada County, California (Table 3.1.8.1) with a chemical composition of {Ca2.99Mn 0.01}

3+ Σ3.00[Cr1.73Al0.21Fe 0.05Ti0.01]Σ1.98(Si3.00)O12. In Figure 3.1.8.2, the {X} and (Z) sites cations from

Novak & Gibbs (1971) fall in line with the data calculated from JTC-1 fully occupied by Ca in the {X} site and Si in the (Z) site (~3.00 apfu) respectively. The [Y] site displays significant differences in cation distribution in JTC-1 as to Novak and Gibbs (1971). The maximum Cr3+ difference between JTC-1 and (Novak and Gibbs 1971) is 1.016 apfu from 0.714 (JTC-1 pt. 25) to 1.73 apfu (Novak and Gibbs 1971). In addition, the Fe3+ maximum difference is 1.135 apfu from 1.185 (JTC-1) to Novak and Gibbs (1971) of 0.05 apfu. This results in contrasting compositions where JTC-1 (phase-1: Uv9Adr88Grs2 and phase-2: Uv30Adr64Grs3) is significantly lower than Novak and Gibbs (1971) (Uv87Grs11Adr2) sample comprising of a greater Uv component with a significantly reduced Adr end-member. According to Cook (1998), the discovery of uvarovites in Jacksonville, California has only been recent, occurring in small clusters of attractive crystals up to 5 mm. The Uv obtained from Washington, California by

Novak and Gibbs (1971) occurs at a different locality, in which the conditions of Uv formation could be significantly different compared to the JTC-1 sample of this thesis.

FIN-1 is compared to previous studies from Knorring et al. (1986) 45 Uv samples represented with a white background in Figure 3.1.8.3. Additional data from Amthauer et al.

(1976) (pt. 11 in orange), Langer et al. (2004) (pt. 26 in blue), Diella et al. (2004) (pt. 30 in green), Taran et al. (1994) (pt. 35 in purple), and Menzer (1929) (pt. 50 in blue) with Uv samples of similar compositions derived from Outokumpu, Finland are also used to support the data obtained from EMPA of FIN-1. A total of 50 data points were obtained from literature studies and are compared to the 15 data analyzed points of FIN-1.

The {X} site shows Ca as the dominant cation across all analyzed points for both FIN-1 and literature data (Figure 3.1.8.3a). Knorring et al. (1986) samples from one to ten show lower Ca2+ apfu values compared to the rest of the literature data. At point 35 Taran et al. (1994) Uv sample has elevated Ca2+ cations greater than 3.00 apfu. The (Z) site displays literature values of Si4+ apfu coincide with the Si4+ values of FIN-1, indicating near full occupancy. Taran et al (1994) displays the lowest Si4+ apfu (<2.90) with the highest elevated Al3+ apfu (0.14). [Y] site partitioning illustrates a pronounced progression of Cr3+ atoms across all analyzed points with a proportional decrease in Al3+ atoms. The EMPA data points derived from FIN-1 are consistent with the overall trends of the literature data. Menzer (1929) illustrates the highest recorded Cr3+ apfu of 1.79 and the lowest Al3+ apfu of 0.19. Knorring et al. (1986) samples from points 34, and 39 to 49 have elevated V3+ apfu resulting in a larger Goldmanite composition in comparison to the rest of the Uv samples recorded from Outokumpu, Finland.

X site

3.000

2.500

2.000 This study Ca Mn2+ a Mg 1.500 Novak & Gibbs

(Ca, Mg, (Ca, Mn ) (1971)

apfu 1.000

0.500

0.000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2.000 Y site 1.800 Fe3+

1.600

1.400 This study Novak & Gibbs Cr (1971) 1.200 Fe3+ Al , Al, Si, Ti, V ) V Ti, Al, Si, , Si 3+ 1.000 Ti Mg b V 0.800

0.600 (Cr, Mg, Fe (Cr,

0.400

apfu Cr

0.200

0.000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Z site

3.000

2.500

2.000 This study Si Al c

(Si, Al) (Si, Novak & Gibbs 1.500 (1971)

apfu

1.000

0.500

0.000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Points Figure 3.1.8.2. Apfu distribution of calculated EMPA data for JTC-1 compared to Novak and Gibbs (1971) Uv sample from Washington, Nevada County, California represented as shapes outlined in black (pt. 26). a. {X} site contains Ca2+ as the dominant cation. b. [Y] site displays a gradual increase in Cr3+ and decreasing Fe3+. The literature data show an average chemical composition of Uv garnet with distinctively high Cr3+ content with trace amounts of Fe3+ apfu, contrasting from the results of JTC-1. c. (Z) site partitioning with Si4+ as the dominant cation.

X site a

3.000

)

2+ 2.500

2.000 This study , Mg, Fe Ca 2+ Mg Mn2+ 1.500 Literature data (Ca, Mn (Ca,

1.000 apfu

0.500

0.000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49

1.800 Y site b

1.600

1.400 Cr , Mg, Si, V) , Mg, Si,

3+ Cr* This study Literature data 1.200 Cr

, Mn Al 2+ 1.000 Fe3+ Ti , Fe V 3+ Al* 0.800 Si Mg

0.600 Al 0.400 (Cr, Al, Ti, Fe Ti, Al, (Cr,

apfu 0.200

0.000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49

Z site c 3.000

2.500

2.000 This study Si Al (Si, Al) (Si, 1.500 Literature data apfu

1.000

0.500

0.000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 Points Figure 3.1.8.3. Apfu distribution of calculated EMPA data for FIN-1 compared with literature data represented as hollow shapes in black. The coloured background display the distinction from literature data samples, Knorring et al. (1986) in white, Amthauer et al. (1976) pt. 11 in orange, Langer et al. (2004) pt. 26 in blue, Diella et al. (2004) pt. 26 in green, Taran et al. (1994) pt. 35 in purple, and Menzer (1928) pt. 50 in light red. a. {X} site contain Ca2+ as the dominant cation. b. [Y] site show a gradual increase in Cr3+ and decreasing Fe3+. c. (Z) site displays Si4+ as the dominant cation.

3.2 Synchrotron High Resolution Powder X-Ray Diffraction (HRPXRD) Results

Detection of two, three, and four individual intergrown cubic phases of Uv were found in all samples analyzed by HRPXRD with the exception of JTC*-5s, which only has one cubic phase. SAR-1 comprises of 3 phases, in contrast to SAR-2, STZ-1, and JTC-1 all containing two phases each, while lastly FIN-1 comprise four phases of Uv garnet. Both single and multiple phases Rietveld refinements were completed for all samples to compare results and to visually illustrate the key differences between the observed and calculated peak profiles. The R (F2) is a measure of how well the calculated data matches the observed data, such that a smaller value corresponds to a more precise fit with minimal change in the difference curve of the HRPXRD traces. Refinements are based on the dominant neutral cations for uvarovite in the {X}, [Y], and

(Z) sites are as follows: Ca2+, Cr3+, site, and Si4+, respectively. Single-phase refinement results indicate that SAR-1s, SAR-2s, STZ-3s, JTC-4s, JTC*-5s, and FIN-6s are most similar to the dominant phase for each corresponding Uv sample from multiple-phase refinements (e.g. SAR-

1a, SAR-2a, STZ-3a, JTC-4b, and FIN-6a, respectively). HRPXRD analyses have distinguished between individual phases of uvarovite that EMPA, single crystal, and conventional powder X- ray diffraction techniques cannot.

3.2.1 Sarany, Urals, Russia (SAR-1)

Rietveld refinement identified three cubic Uv phases in SAR-1 (SAR-1a, SAR-1b, and

SAR-1c). The data was refined to a reduced χ2 of 1.422 and an R (F2) of 7.75 %. Weight percentages and a unit-cell parameter of SAR-1a, SAR-1b, and SAR-1c are as follows: 51.13%,

11.93161(1) Å; 14.14%, 11.91425(2) Å; and 34.73%, 11.92752(1), respectively (Table 3.2.1).

Structural refinement data are tabulated in Table 3.2.1. The refinement had a 2θ range from 3 -

50° and contains 46996 data points with 2028 observed reflections. In comparison, a single- phase of SAR-1s was completed and refined to a reduced χ2 of 1.516 and R (F2) of 7.89 % with an a unit-cell parameter of 11.92794(4) Å.

Isotropic displacement parameters, site occupancy factors (sofs), and atom coordinates are tabulated in Table 3.2.2. The variations in both refinement and EMPA sofs in the {X}, [Y], and (Z) sites indicate the slight compositional changes between the three phases. SAR-1a represents the dominant phase comprising of sof values that are the largest and most similar to the EMPA sofs compared to SAR-1b and SAR-1c. The site occupancy factors (sofs) for SAR-1a are as follows: Ca (X) = 0.928(4), Cr (Y) = 0.728(3), and Si (Z) = 0.926(5). Sofs for SAR-1b are as follows: Ca (X) = 0.845(9), Cr (Y) = 0.577(8), and Si (Z) = 0.993(1). Lastly, the site occupancy sofs for SAR-1c are as follows: Ca (X) = 0.987(5), Cr (Y) = 0.687(4), and Si (Z) =

0.884(6). There are similarities between the sofs obtained from both HRPXRD and EMPA; however, refinement sofs are significantly different for the [Y] site in each phase, whereas the

{X} and (Z) sites have slightly less variation. Refinement sofs for the [Y] site range from

0.577(8) in SAR-1b to 0.728(3) in SAR-1a, with a difference of 0.151. The large variation in refinement sofs in the [Y] site result from differing proportions of Cr3+ and Al3+ cations in each

75 phase. As a result of the complexity of SAR-1 during Rietveld refinement, the displacement parameters (U) along with the sofs were constrained together for the three phases.

The visual contrasts between single and multiple phase refinement for SAR-1 is illustrated in Figure 3.2.1. The high angle region beyond 25° in the HRPXRD trace was scaled by 20x to amplify the difference curve as well as the high-angle region. The three-phases of

SAR-1 are structural intergrowths with slight variations in a cell parameters, and are represented as the vertical lines positioned below the diffraction peaks (Figure 3.2.1.d). The difference curve shows a more accurate fit with less variation in the three-phase refinement. The close up view of peak (640) (Figure 3.2.1.1b and d) displays asymmetrical peak broadening, resulting from one or more of the following causes: instrumental error, micro-strain, and/or the crystallite size.

Instrumental broadening is unlikely due to the nature of the experiment using synchrotron high- resolution data. The Lorentzian term LX is closely related to the crystallite size and LY is associated to the micro-strain between atoms. SAR-1 has a refined value of LX at 0; however,

LY possesses a high value indicates the existence of micro-strain in SAR-1. This source is most likely attributed to the lattice mismatch in the expansion or contraction of the minor phases in response to the volume of the dominant phase.

SAR-1 x 20 Single phase

(642) (640)

(640) 1000x Intensity

2θ

(552)

a b

Three phases

(642)

Intensity x 10000 (640) (640) Intensity x 1000x Intensity

2θ (552)

c d 2θ

Figure 3.2.1. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for SAR-1 from Sarany, Urals, Russia. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (640) for the single-phase compared to 3- phase displaying a more accurate fit and reduced difference curve.

Table 3.2.1. HRPXRD data including Rietveld structure refinement statistics for uvarovite samples SAR-1 and SAR-2 1. Sarany, Urals, Russia (SAR-1) 2. Sarany, Urals, Russia (SAR-2) Multi-Phase Single Multi-Phase Single SAR-1a SAR-1b SAR-1c SAR-1s SAR-2a SAR-2b SAR-2s Wt. % 51.13 14.14 34.73 100.00 95.66 4.34 100.00

a (Å) 11.93161(1) 11.91425(2) 11.92752(1) 11.92794(4) 11.96791(3) 11.97700(8) 11.96851(2)

Δa (Å) - 0.01736 0.00409 - - -0.00909 -

Reduced χ2 1.422 1.516 2.235 2.519

R (F2) 0.0775 0.0789 0.0433 0.0467

wRp 0.1010 0.1042 0.0976 0.1037

Data points 46996 46996 46993 46993

N 2028 686 1338 686 obs λ (Å) 0.414237 0.414237 0.413896 0.413896 Each EMPA and HRPXRD phase are correlated as follows, SAR-1: phase-1 = SAR-1b, phase-2 = SAR-1c, and phase-3 = SAR-1a. SAR-2: phase-1 = SAR-2a, and phase-2 = SAR-2b.

Table 3.2.2. Atom coordinates, isotropic displacement parameters, U (x100) (Å2), sofs, and differences between phases for uvarovite samples from Russia: SAR-1 and SAR-2 1. Sarany, Urals, Russia (SAR-1) 2. Sarany, Urals, Russia (SAR-2) Multi-Phase Single Multi-Phase Single

SAR-1a SAR-1b SAR-1c SAR-1s SAR-2a SAR-2b SAR-2s

Ca (X) U 0.449(1) 0.449(1) 0.449(1) 0.437(1) 0.444(9) 0.444(9) 0.435(1) Cr (Y) U 0.186(8) 0.186(8) 0.186(8) 0.227(8) 0.223(6) 0.223(6) 0.196(7)

Si (Z) U 0.295(2) 0.295(2) 0.295(2) 0.371(2) 0.296(1) 0.296(1) 0.287(2)

O x 0.04150(2) 0.0416(4) 0.03562(2) 0.03918(5) 0.03896(5) 0.0471(7) 0.03935(5)

y 0.05149(2) 0.0472(4) 0.04035(2) 0.04666(5) 0.04691(5) 0.0522(7) 0.04721(5)

z 0.65131(2) 0.6553(5) 0.65493(2) 0.65301(5) 0.65337(6) 0.6566(7) 0.65340(5)

U 0.831(2) 0.831(2) 0.831(2) 0.897(2) 0.841(2) 0.841(2) 0.851(2)

Ca (X) sof 0.928(4) 0.845(9) 0.987(5) 0.941(2) 0.952(2) 0.828(1) 0.948(2)

Cr (Y) sof 0.728(3) 0.577(8) 0.687(4) 0.705(1) 0.803(1) 0.889(2) 0.802(1)

Si (Z) sof 0.926(5) 0.993(1) 0.884(6) 0.927(2) 0.916(2) 0.943(2) 0.916(2)

Ca (X) EMPA sof 0.993 0.991 0.992 1.019 1.018

Cr (Y) EMPA sof 0.818 0.750 0.781 0.834 0.849

Si (Z) EMPA sof 1.000 1.000 1.000 0.999 0.999

bX Δ(sof) -0.065 -0.146 -0.005 -0.067 -0.190

Y Δ(sof) -0.090 -0.173 -0.094 -0.031 0.040

Z Δ(sof) -0.074 -0.007 -0.116 -0.083 -0.056

cX Δe -1.300 -2.920 -0.100 -1.340 -3.800

Y Δe -2.160 -4.152 -2.256 -0.744 0.960

Z Δe -1.036 -0.098 -1.624 -1.162 -0.784 aX at (0,1/4,1/8) with Ca dominant, Y at (0,0,0) with Cr dominant, and Z at (3/8,0,1/4) with Si dominant. In the two b and three phase refinements, the U for all atoms were equally constrained. Δ(sof) = sof (HRPXRD refinement) – sof c (EMPA), Δe = electrons (HRPXRD refinement) – electrons (EMPA).

3.2.2 Sarany, Urals, Russia (SAR-2)

HRPXRD results identified two phases of Uv in SAR-2 (SAR-2a and SAR-2b). The data was refined to a reduced χ2 of 2.235 and an R (F2) of 4.33 % containing 46993 data points with

1338 observed reflections. Rietveld refinement data including refinement statistics are tabulated in Table 3.2.1. Weight percentages and a unit-cell parameter of SAR-2a and SAR-2b: 95.66%,

11.96791(3) Å; 4.34%, 11.97700(8) Å respectively. In contrast, a single-phase (SAR-2s) was done and refined to a reduced χ2 of 2.519 and R (F2) of 4.67 %, with an a unit-cell parameter of

11.96851(2) Å.

Isotropic displacement parameters, site occupancy factors (sofs), and atom coordinates are tabulated in Table 3.2.2. Distinctive compositional changes are observed between the two phases of SAR-2 in the {X}, [Y], and (Z) sites for EMPA and refinement sofs. SAR-2a represents the dominant phase in which the sof values are the largest and most similar to the

EMPA sofs compared to SAR-2b. The site occupancy factors (sofs) for SAR-2a are as follows:

Ca (X) = 0.952(2), Cr (Y) = 0.803(1), and Si (Z) = 0.916(2); SAR-2b sofs are as follows: Ca (X)

= 0.828(1), Cr (Y) = 0.889(2), and Si (Z) = 0.943(2). Similarities exist between the sofs obtained from both HRPXRD and EMPA; however, refinement sofs are significantly different for the

{X}, [Y], and (Z) sites in SAR-2b. Refinement sofs for the [Y] site range from 0.803(1) in SAR-

2a to 0.889(2) in SAR-2b, with a difference of 0.086. Variations in refinement sofs in the [Y] site result from differing proportions of Cr3+ and Al3+ cations in each phase. Additionally,

EMPA sofs are larger than the refinement sofs because EMPA takes into account all of the cations present in the corresponding site, whereas refinement sofs consider only the dominant neutral atom for each site. During Rietveld refinement for SAR-2, the isotropic displacement parameters (U) along with the sofs were constrained together for the two phases.

In Figure 3.2.2, shows the XRD traces of both a single and two-phase refinement of

SAR-2. Peak broadening is distinctly observed whereas asymmetrical peaks are less pronounced. The high-angle region beyond 25° in the HRPXRD trace was scaled by 20x to amplify the difference curve as well as the high-angle region. The two-phase structural intergrowths of SAR-2 have slight variations in a cell parameters, and are represented as the vertical lines positioned below the diffraction peaks (Figure 3.2.2.d). The calculated (continuous green line) in the two-phase refinement fits more accurately to the observed (red crosses) than the single-phase refinement. A zoomed in view (Figure 3.2.2.) shows the calculated and continuous profiles in peak (14,4,2) to be more aligned and have more precision in the two-phase refinement.

SAR-2 x 20 Single phase (14,4,2) (14,4,2) Intensity x 1000x Intensity (14,4,0) 2θ (14,3,3)

a b

Two phases (14,4,2) (14,4,2) Intensity x 10000 Intensity x 1000x Intensity (14,4,0) 2θ

(14,3,3)

c d 2θ Figure 3.2.2. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for SAR-2 from Sarany, Urals, Russia. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (14,4,2) for the single-phase compared to 2-phase displaying a more accurate fit and reduced difference curve.

3.2.3 Zermatt, Switzerland (STZ-1)

Two phases of Uv garnet were detected from the Swiss sample: STZ-3a and STZ-3b.

The two–phase refinement was reduced to a χ2 of 1.217 and an R (F2) of 5.81 % with 1389 observed reflections consisting of 46993 data points. Weight percentages and a unit-cell parameter of STZ-3a and STZ-3b are as follows: 84.80%, 11.94489(3) Å and 15.20%,

11.96584(2) Å, respectively. Additional refinement statistics are tabulated in Table 3.2.3. A single-phase of STZ-3s was refined to a reduced χ2 of 2.704 and R (F2) of 6.58 % Å with an a unit-cell parameter of 11.96851(2) Å. Isotropic displacement parameters, site occupancy factors

(sofs), and atom coordinates are tabulated in Table 3.2.3.

HRPXRD and EMPA sofs are similar to each other; however, refinement sofs have different values. Minor compositional changes occur between the two phases of STZ-1 in the

{X}, [Y], and (Z) sites for EMPA and refinement sofs. STZ-3a represents the dominant phase where the sof values are the largest and most similar to the EMPA sofs compared to STZ-3b.

The site occupancy factors (sofs) for STZ-3a are as follows: Ca (X) = 0.946(2), Cr (Y) =

0.719(1), and Si (Z) = 0.923(2); and STZ-3b sofs are as follows: Ca (X) = 0.945(5), Cr (Y) =

0.813(4), and Si (Z) = 0.928(5). The {X} and (Z) sites possess the least amount of change in refinement sofs, whereas the [Y] site contains the largest variation. Refinement sofs for the [Y] site range from 0.719(1) in STZ-3a to 0.813(4) in STZ-3b, with a difference of 0.094. The differences in refinement sofs in the [Y] site are the result of variable amounts of Cr3+ and Al3+ cations in each phase. The isotropic displacement parameters (U) along with the sofs were constrained together for the two phases of STZ-1 during Rietveld refinement.

Single and two-phase refinement traces for STZ-1 illustrates the visible contrasts in

Figure 3.2.3. The asymmetry observed in all peaks in the diffraction pattern is the result of two

83 cubic phase overgrowths of uvarovite with differing a unit cell parameters, and are depicted as the vertical lines situated below the diffraction pattern (Figure 3.2.3.d). The calculated

(continuous green line) in the two-phase refinement displays a more accurate fit with the addition of a second phase to the observed (red crosses) than in the single-phase refinement. Figure

3.2.3.c shows a close up view of peak (842) with a near exact overlay of calculated and continuous profiles showing little variation in the difference curve.

STZ-1 Single phase (842)

(842) (840) (664) Intensity x 1000x Intensity

2θ (761)

a b

Two phases (842)

(840) Intensity x 10000 (842) (664) Intensity x 1000x Intensity

2θ (761)

c d

2θ Figure 3.2.3. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for STZ-1 from Switzerland. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single-phase compared to 2-phase displaying a more accurate fit and reduced difference curve.

Table 3.2.3. HRPXRD data including selected interatomic distances (Å) and Rietveld structure refinement statistics for uvarovite samples STZ-1 and JTC-1 3. Switzerland (STZ-1) 4. Jacksonville, Tuolumne County, California (JTC-1) Multi-Phase Single Multi-Phase (Dark) Single (Dark) Single (Light) STZ-3a STZ-3b STZ-3s JTC-4a JTC-4b JTC-4s JTC*-5s Wt. % 84.80 15.20 100.00 16.21 83.79 100.00 100.00 a (Å) 11.94489(3) 11.96584(2) 11.94598(3) 12.05305(2) 12.04647(2) 12.04856(3) 12.05238(1) Δa (Å) - -0.02095 - - 0.00658 - - Reduced χ2 1.217 2.704 1.395 2.783 3.667

R (F2) 0.0581 0.0658 0.0509 0.0665 0.0357

wRp 0.0761 0.1134 0.0921 0.1143 0.1061

Data points 46993 46993 46996 45993 46996

N 1389 701 1373 703 686 obs λ (Å) 0.413896 0.41389(6) 0.414237 0.414237 0.414237

Each EMPA and HRPXRD phase are correlated as follows, SAR-1: phase-1 = SAR-1b, phase-2 = SAR-1c, and phase-3 = SAR-1a. SAR-2: phase-1 = SAR-2a, and phase-2 = SAR-2b. STZ-1: phase-1 = STZ-3a, and phase-2 = STZ-3b. JTC-1: phase-1 = JTC-4a, phase-2 = JTC-4b, and phase-1 = JTC*-5s.

Table 3.2.4. Atom coordinates, isotropic displacement parameters, U (x100) (Å2), sofs, and differences between phases for uvarovite samples from Switzerland and California, respectively: STZ-1 and JTC-1 3. Switzerland (STZ-1) 4. Jacksonville, Tuolumne County, California (JTC-1) Multi-Phase Single Multi-Phase (Dark) Single (Dark) Single (Light)

STZ-3a STZ-3b STZ-3s JTC-4a JTC-4b JTC-4s JTC*-5s

Ca (X) U 0.486(9) 0.486(9) 0.406(1) 0.469(9) 0.469(9) 0.493(2) 0.4762(3) Cr (Y) U 0.238(6) 0.238(6) 0.196(9) 0.259(5) 0.259(5) 0.267(8) 0.2562(3)

Si (Z) U 0.340(1) 0.340(1) 0.360(2) 0.363(1) 0.363(1) 0.365(2) 0.2362(3)

O x 0.03860(5) 0.03917(2) 0.03869(6) 0.03863(2) 0.03965(6) 0.03946(7) 0.03947(5)

y 0.04653(5) 0.04830(2) 0.04681(5) 0.04803(2) 0.04860(6) 0.04851(6) 0.04866(5)

z 0.65298(5) 0.65294(2) 0.65287(5) 0.65530(2) 0.65512(6) 0.65513(7) 0.65542(5)

U 0.924(1) 0.924(14) 0.909(2) 0.862(2) 0.862(2) 0.843(2) 0.4362(3)

Ca (X) sof 0.946(2) 0.945(5) 0.940(2) 0.968(5) 0.935(2) 0.944(2) 0.984(1)

Cr (Y) sof 0.719(1) 0.813(4) 0.724(1) 1.025(5) 0.986(2) 0.993(2) 1.030(1)

Si (Z) sof 0.923(2) 0.928(5) 0.923(2) 0.924(5) 0.941(2) 0.942(3) 0.947(1)

Ca (X) EMPA sof 0.995 0.998 0.996 1.002 0.996

Cr (Y) EMPA sof 0.785 0.861 1.064 1.033 1.064

Si (Z) EMPA sof 1.000 1.000 1.000 1.000 1.000

bX Δ(sof) -0.049 -0.053 -0.028 -0.067 -0.012

Y Δ(sof) -0.066 -0.048 -0.039 -0.047 -0.034

Z Δ(sof) -0.077 -0.072 -0.076 -0.059 -0.053

cX Δe -0.980 -1.060 -0.560 -1.340 -0.240

Y Δe -1.584 -1.152 -0.936 -1.128 -0.816

Z Δe -1.078 -1.008 -1.064 -0.826 -0.742 aX at (0,1/4,1/8) with Ca dominant, Y at (0,0,0) with Cr dominant, and Z at (3/8,0,1/4) with Si dominant. In the two-phase b c refinements, the U for all atoms were equally constrained. Δ(sof) = sof (HRPXRD refinement) – sof (EMPA), Δe = electrons (HRPXRD refinement) – electrons (EMPA).

3.2.4 Jacksonville, Tuolumne County, California, USA (JTC-1)

Rietveld refinement detected two-phases of cubic uvarovite in JTC-1: JTC-4a and JTC-

4b. The analysis was refined to a reduced χ2 of 1.395 and an R (F2) of 5.09 %. Refinement data statistics are listed in Table 3.2.3. Weight percentages and a unit-cell parameter of JTC-4a and

JTC-4b are as follows: 16.21%, 12.05305(2) Å; and 83.79%, 12.04647(2) Å, respectively (Table

3.2.1). The refinement contains 46996 data points with 1373 observed reflections. In comparison, a single-phase of JTC-4s was refined to a reduced χ2 of 2.783 and an R (F2) of 6.65

% with an a unit-cell parameter of 12.04856(3) Å.

Atomic coordinates, sofs, and isotropic displacement parameters are tabulated in Table

3.2.3. Refinement sofs and EMPA sofs have slightly different values and are the result of minor compositional changes between the two phases in the {X}, [Y], and (Z) sites. JTC-4b represents the dominant phase, containing the largest sof values and is most similar to the EMPA sofs compared to JTC-4a. The site occupancy factors (sofs) for JTC-4b are as follows: Ca (X) =

0.968(5), Cr (Y) = 1.025(5), and Si (Z) = 0.924(5); and JTC-4a sofs are as follows: Ca (X) =

0.935(2), Cr (Y) = 0.986(2), and Si (Z) = 0.941(2). The most variation occurs in the refinement sofs for the [Y] site in each phase, compared to the {X} and (Z) sites comprises of very little change. Refinement sofs for the [Y] site range from 0.986(2) in JTC-4b to 1.025(5) in JTC-4a, with a difference of 0.039. The different cation proportions of Cr3+ and Al3+ in each phase in the

[Y] site is the cause for the large variation in refinement sofs. The sofs along with the isotropic displacement parameters (U) were constrained together for the two phases of JTC-1 during

Rietveld refinement.

Comparison between a single phase and a two-phase refinement for JTC-1 is modeled in

Figure 3.2.4. The two-phases of JTC-1 are structural intergrowths of similar but distinct a cell

88 parameters, and are seen as the vertical lines located below the diffraction peaks (Figure 3.2.4).

The difference curve shows a more accurate fit with the multi-phase refinement. Peak (640) displays peak asymmetry and splitting caused by the superposition of multiple cubic phases of

Uv within a reduced difference curve in the two-phase refinement (Figure 3.2.4.d).

Sample JTC*-5s contains one phase of cubic uvarovite. The data was refined to a reduced χ2 of 3.667, and R (F2) of 3.57 %, with an a unit-cell parameter of 12.05238(1) Å. The refinement contains 46996 data points with 686 observed reflections. The site occupancy factors

(sofs) for JTC*-5s are as follows: Ca (X) = 0.984(1), Cr (Y) = 1.030(1), and Si (Z) = 0.947(1).

The most variation occurs in the refinement sofs for the [Y] site compared to the {X} and (Z) sites comprises of very little change. The (842) peak in Figure 3.2.5, along with higher angle peaks throughout the diffraction trace are sharp and symmetrical with no deviation such as peak splitting or broadening to indicate any additional phases of cubic Uv.

JTC-1 Single phase

(840) (842) (842) (664) Intensity x 1000x Intensity (761) 2θ

a b Two phases

(840) (842) Intensity x 10000 (842) (664) Intensity x 1000x Intensity

2θ (761)

c d 2θ Figure 3.2.4. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for JTC-1 from Jacksonville, Tuolumne County, California. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single-phase compared to 2-phase displaying a more accurate fit and reduced difference curve.

JTC*-5s

(842) Intensity x Intensity 1000

2θ

(840) (842) Intensity x 10000

(664)

(761)

2θ

3.2.5 Outokumpu, Finland (FIN-1)

Results determined the presence of four phases in FIN-1: FIN-6a, FIN-6b, FIN-6c, and

FIN-6d. The data was refined to a reduced χ2 of 4.014 and an R (F2) of 6.53 %. The refinement contains 46996 data points with 2606 observed reflections. Weight percentages and a unit-cell parameters of FIN-6a, FIN-6b, FIN-6c, and FIN-6d are as follows: 92.33%, 11.95356(2) Å;

3.28%, 11.93714(9) Å; 1.03%, 11.9670(3) Å, and 3.36%, 11.95334(2), respectively (Table

3.2.5). To compare, a single-phase of FIN-6s was refined to a reduced χ2 of 5.588 and an R (F2) of 6.36 % containing a unit-cell parameter of 11.95334(2) Å.

Sofs, isotropic displacement parameters, and atom coordinates are tabulated in Table

3.2.6. FIN-6a represents the dominant phase in which the sof values are the largest and most similar to the EMPA sofs compared to FIN-6b, FIN-6c, and FIN-6d. The sofs for FIN-6a are as follows: Ca (X) = 0.940(2), Cr (Y) = 0.803(2), and Si (Z) = 0.925(2). Additionally, the (sofs) for the three other phases are as follows: FIN-6b: Ca (X) = 0.996(2), Cr (Y) = 0.727(1), and Si (Z) =

0.912(2); FIN-6c: Ca (X) = 0.84(4), Cr (Y) = 0.95(4), and Si (Z) = 0.97(6); and FIN-6d: Ca (X) =

0.893(2), Cr (Y) = 0.685(1), and Si (Z) =0.938(2). FIN-6a and FIN-6b are the most similar to their EMPA sofs in all sites, whereas FIN-6c differs significantly in the {X} site while FIN-6d contains the most change in the {X} and [Y] sites. EMPA sofs can vary quite differently compared to refinement sofs because in EMPA all cations present in each corresponding site are considered, in contrast to HRPXRD that takes into account only the dominant neutral cation in each site. The large variations in refinement sofs in the [Y] site result from differing proportions of Cr3+ and Al3+ cations in each phase. As a result of the complexity of the four phases in FIN-1 during Rietveld refinement, the displacement parameters (U) along with the sofs were constrained together.

Single and two-phase refinement traces for FIN-1 illustrates the visible contrasts in

Figure 3.2.6. The noticeable broadening and asymmetry in the peaks becomes more apparent in higher angle and is observed in all peaks in the diffraction pattern. The results from the mixture of the four cubic phases of uvarovite containing multiple structural intergrowths that only

HRPXRD can detect. The calculated (continuous green line) in the four-phase refinement displays a more accurate fit with the presence of the additional phases showing less variation in the difference curve to the observed (red crosses) than in the single-phase refinement. Figure

3.2.6.d shows a closer view of peak (842) with a more aligned overlay of calculated and continuous profiles displaying little variation in the difference curve.

FIN-1 x 20 Single phase

(840) (842)

(842) Intensity x 1000x Intensity

2θ

a b

Four phases

(840) (842) Intensity x 10000 (842) Intensity x 1000x Intensity

2θ

c d 2θ Figure 3.2.6. Comparison of completed HRPXRD traces for a. single-phase refinement and b. multiple-phase refinement for FIN-1 from Outokumpu, Finland. The difference curve (Iobs- Icalc) is shown at the bottom in purple with the calculated (continuous green line) and observed (red crosses) profiles. Zoomed in insert shows a more asymmetrical peak (842) for the single-phase compared to 4- phase displaying a more accurate fit and reduced difference curve.

Table 3.2.5. HRPXRD data including selected interatomic distances (Å) and Rietveld structure refinement statistics for uvarovite samples FIN-1 5. Outokumpu, Finland (FIN-1) Multi-Phase Single FIN-6a FIN-6b FIN-6c FIN-6d FIN-6s Wt. % 92.330 3.28 1.03 3.36 100.00 a (Å) 11.95356(2) 11.93714(9) 11.9670(3) 11.9261(7) 11.95334(2) Δa (Å) - 0.01642 -0.01344 0.02746 - Reduced χ2 4.014 5.588

R (F2) 0.0653 0.0636

wRp 0.1134 0.1338

Data points 46996 46996

N 2606 obs 681 λ (Å) 0.41423(7) 0.41423(7)

Each EMPA and HRPXRD phase are correlated as follows, FIN-1: phase-1 = FIN-6b, phase-2 = FIN-6c, phase-3 = FIN-6d, and phase-4 = FIN-6a

Table 3.2.6. Atom coordinates, isotropic displacement parameters, U (x100) (Å2), sofs, and differences between phases for uvarovite sample from Finland: FIN-1 5. Outokumpu, Finland (FIN-1) Multi-Phase Single

FIN-6a FIN-6b FIN-6c FIN-6d FIN-6s

Ca (X) U 0.454(1) 0.454(1) 0.454(1) 0.454(1) 0.482(4) Cr (Y) U 0.214(7) 0.214(7) 0.214(7) 0.214(7) 0.262(4) Si (Z) U 0.344(2) 0.344(2)) 0.344(2) 0.344(2) 0.242(4) O x 0.03850(6) 0.0366(7) 0.0573(2) 0.0406(7) 0.03836(6) y 0.04654(6) 0.0462(7) 0.0838(2) 0.0468(7) 0.04676(6)

z 0.65398(6) 0.6522(8) 0.6567(2) 0.6584(9) 0.65382(6)

U 0.892(2) 0.892(2) 0.892(2) 0.892(2) 0.442(4)

Ca (X) sof 0.940(2) 0.996(2) 0.84(4) 0.893(2) 0.951(6) Cr (Y) sof 0.803(2) 0.727(1) 0.95(4) 0.685(1) 0.828(6) Si (Z) sof 0.925(2) 0.912(2) 0.97(6) 0.938(2) 0.982(6) Ca (X) EMPA sof 0.997 0.998 0.984 0.999

Cr (Y) EMPA sof 0.867 0.813 0.890 0.767

Si (Z) EMPA sof 1.000 1.000 1.000 1.000 bX Δ(sof) -0.057 -0.003 -0.144 -0.107

Y Δ(sof) -0.064 -0.086 0.060 -0.082

Z Δ(sof) -0.075 -0.081 -0.030 -0.063 cX Δe -1.140 -0.060 -2.880 -2.140

Y Δe -1.368 -0.072 -3.456 -2.568

Z Δe -1.050 -1.134 -0.420 -0.882 aX at (0,1/4,1/8) with Ca dominant, Y at (0,0,0) with Cr dominant, and Z at (3/8,0,1/4) with Si dominant. In the two phase refinements, the U for all atoms were equally constrained. bΔ(sof) = c sof (HRPXRD refinement) – sof (EMPA), Δe = electrons (HRPXRD refinement) – electrons (EMPA)

3.2.6 Unit-Cell Parameter Variations

As previously mentioned, the weight percent and a unit-cell parameters for all single- phase refinements are as follows: SAR-1s, 11.92794(4) Å; SAR-2s, 11.96851(2) Å; STZ-3s,

11.92794(4) Å; JTC-4s, 12.04856(3) Å; JTC*-5s, 12.055238 Å; and FIN-6s, 11.95334(2) Å.

Additionally, the a unit-cell parameters for each multiple phase refinement are as follows: SAR-

1a, 11.93161(1) Å; SAR-1b, 11.91425(2) Å; SAR-1c, 11.92752(1); SAR-2a, 11.96791(3) Å;

SAR-2b 11.97700(8) Å; STZ-3a: 11.94489(3) Å; STZ-3b 11.96584(2) Å; JTC-4a, 12.05305(2)

Å; JTC-4b, 12.04647(2) Å; FIN-6a, 11.95356(2) Å; FIN-6b, 11.93714(9) Å; FIN-6c, 11.9670(3)

Å; and lastly, FIN-6d, 11.9261(7) Å. All of the a unit-cell parameters in this study fall within range in between Grs and Adr end-members, as expected. Grossular (11.845(1) Å) typically has the lowest a unit-cell parameters of the ugrandite series, with andradite (12.058(1) Å) containing the largest, while uvarovite (11.988(1) Å) possess intermediate values (Novak and Gibbs, 1971).

The a unit cell parameters obtained from all samples range from 11.91425(2) Å in SAR-1b to

12.05305(2) Å in JTC-4a.

SAR-1a, SAR-1b, FIN-6b, and FIN-6d are most similar to the following: 11.9254 Å from

Wilder and Andrut (2001) Ska-1 Ural Mountains birefringent uvarovite, Wan and Yeh (1984) uvarovite, 11.912 Å from Fengtien, eastern Taiwan, 11.922 Å reported from Proenza et al.

(1999) Uv from Cuba, Diella et al. (2004) Outokumpu Uv with 11.9288(1) Å, and Knorring’s

(1951) Uv also from Outokumpu with a unit cell of 11.922 Å. SAR-1c is closely similar to

Righter et al. (2011) Uv sample, R060477, with an a cell parameter of 11.9204(8) Å. SAR-2a and SAR-2b have similar a unit-cell parameters to Novak and Gibb’s (1971) uvarovite from

Washington, California containing 11.988(1) Å, Deer et al (1997) Uv with 11.996 Å, as well as

Carda et al (1994) synthetic Uv samples of a unit-cell parameters of 11.9947(10), 11.9939(9),

11.9910(16), and 11.9903(18) Å. STZ-3a, STZ-3b, FIN-6a, and FIN-6b possess a-cell parameters comparable to 11.9675, 11.9651, 11.9583, 11.9591, and 11.9576 Å values Wilder and Andrut (2001) reported for their birefringent uvarovites. Additionally, they are also similar to Sawada (1997) Uv sample with 11.956(1) Å and to Menzer’s (1929) Uv with a unit-cell parameter of 11.950 Å. Synthetic uvarovite studies from Fan et al. (2015), Carda et al. (1994), and Skinner (1956) with a unit-cell parameters of 12.021, 12.0205(5), and 12.000 Å, respectively, are closely related to the values observed in JTC-4a, JTC-4b, and JTC*-5s.

Overall, the a-cell parameters of all phases in SAR-1, SAR-2, STZ-1, JTC-1, and FIN-1 are all consistent with values in literature data.

The measurement of birefringence for multiple phase garnets is describe as Δa, which is the calculated difference between a unit-cell parameters between the dominant and minor phases

(Table 3.2.1, 3.2.3, and 3.2.5; Kitamura and Komatsu 1978). The calculated birefringence of

SAR-1, SAR-2, STZ-1, JTC-1, and FIN-1 are comparable to the measured birefringence from literature studies. The Δa of SAR-1c, SAR-2b and JTC-4b, (0.00409, 0.000909, and 0.00658, respectively) are within range and compare well with the reported birefringence of up to 0.006 from Proenza et al. (1999), Andrut and Wildner (2001), and even up to 0.008 from Spiridonov et al (2006). The smallest calculated birefringence is observed in Sarany, Urals, Russia (SAR-2) with Δa = 0.00909. Yet, due to SAR-2b’s small weight percentage of 4.34%, this can lead to a higher degree of error. Similarly, the largest calculated birefringence occurs in Uv sample from

Outokumpu, Finland (FIN-1) with Δa = 0.02746. The low weight percentage of FIN-6d (3.36%) can cause larger degrees of error and may not accurately represent the largest calculated birefringence. Uvarovite from Sarany, Urals, Russia (SAR-1) shows a more accurate measure of

98 the calculated birefringence between SAR-1c to SAR-1a, with a Δa = 0.00409, as SAR-1c has a significant weight percentage of 34.73%.

3.2.7 Site Occupancy Factors (sofs) and Chemical Composition

The a unit-cell parameter from one phase to the other in each Uv sample analyzed is the result from the differences in chemical composition among each phase. To correlate the results obtained from both EMPA and HRPXRD, a closer evaluation on the site occupancy factors (sof) for each single and multiple phases were observed. Results identified an equivalent number of

EMPA phases that correspond to an HRPXRD phase. The most similar HRPXRD phase closely resembles the sof values for each EMPA was calculated together to determine the differences in electrons. Additionally, the sofs and the a unit-cell parameters of the single-phase refinements are most comparable to the dominant phase of the multiple phase refinement. For example,

SAR-1s is most similar to SAR-1a; SAR-2s is most related to SAR-2a; STZ-3s is closely related to STZ-3a, JTC-4s is closely similar to JTC-4b, and lastly, FIN-6s similar to FIN-6a. However,

JTC*-5s is more related to the less dominant phase of JTC-4a.

Each EMPA phase and HRPXRD multiphase are tabulated in Table 3.2.7 and are correlated as follows, SAR-1: Uv39Grs57Adr3 (phase-1) = SAR-1b, Uv48Grs49Adr2 (phase-2) =

SAR-1c, and Uv56Grs42Adr1 (phase-3) = SAR-1a. SAR-2: Uv58Grs29Adr3 (phase-1) = SAR-2a, and Uv62Grs26Adr3 (phase-2) = SAR-2b. STZ-1: Uv22Grs51Adr24 (phase-1) = STZ-3a, and

Uv43Grs34Adr21 (phase-2) = STZ-3b. JTC-1: Uv9Adr88Grs2 (phase-1) = JTC-4a and JTC*-5s, and Uv30Adr64Grs3 (phase-2) = JTC-4b. FIN-1: Uv46Grs46Mmt3 (phase-1) = FIN-6b,

Uv56Grs37Adr2 (phase-2) = FIN-6c, Uv68Grs27Adr1 (phase-3) = FIN-6d, and Uv71Grs24Sps1

(phase-4) = FIN-6a. Comparison of all samples studied in correlation to each respective dominant phase, the refinement sofs ranges from: in the X site, 0.928(4) in SAR-1 to 0.95.2(2) in

SAR-2; Y site, 0.719(1) in STZ-1 to 0.986(2) in JTC-4b, and lastly in the Z site, 0.916(2) in

SAR-2 to 0.941(2) in JTC-4b. {X} and (Z) sites are nearly fully occupied with Ca2+ and Si4+

100 respectively, while the [Y] site differs from full occupancy and contains cations, primarily Fe3+ and Al3+ that fill in the remaining vacant octahedral sites. EMPA sofs are higher than refinement sofs because of the nature of EMPA taking into consideration all of the possible cations present for each respective site, whereas in the refinement sofs the dominant neutral cations (Ca, Cr, and

Si) are the only ones being considered for each respective site, producing a more accurate value.

101

Table 3.2.7. Uvarovite EMPA phase end-member relationships to corresponding HRPXRD single and multiple phases EMPA HRPXRD Multi-Phase Multi-Phase HRPXRD Single - Phase Uv End-Member Phase Multi-Phase a (Å) Wt. % Single-Phase a (Å) SAR-1 1 Uv Grs Adr SAR-1b 11.91425(2) 14.14 - - 39 57 3 2 Uv Grs Adr SAR-1c 11.92752(1) - - 48 49 2 34.73 3 Uv Grs Adr SAR-1a 11.93161(1) 51.13 SAR-1s 11.92794(4) 56 42 1

SAR -2 1 Uv Grs Adr SAR-2a 11.96791(3) 95.66 SAR-2s 11.96851(2) 58 29 3 2 Uv Grs Adr SAR-2b 11.97700(8) 4.34 - - 62 26 3 SKR -1 1 Uv Grs Sch - - - - - 60 25 5 2 Uv Grs Sch - - - - - 68 17 5 STZ -1 1 Uv Grs Adr STZ -3a 11.94489(3) 84.80 STZ -3s 11.94598(3) 22 51 24 2 Uv Grs Adr STZ-3b 11.96584(2) 15.20 - - 43 34 21 JTC -1 1 Uv Adr Grs JTC -4a 12.05305(2) 16.21 - - 9 88 2 JTC-4s 12.04856(3) 2 Uv Adr Grs JTC-4b 12.04647(2) 83.79 30 64 3 JTC*-5s 12.05238(1)

FIN -1 1 Uv Grs Mmt FIN -6b 11.93714(9) 3.28 - - 46 46 3 2 Uv Grs Adr FIN-6c 11.9670(3) 1.03 - - 56 37 2 3 Uv Grs Adr FIN-6d - - 68 27 1 11.9261(7) 3.36 4 Uv71Grs24Sps1 FIN-6a 11.95356(2) 92.33 FIN-6s 11.95334(2)

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3.2.8 Isotropic Displacement Parameters (U)

The isotropic displacement parameters, U, were refined and constrained to be the same for all Uv phases in each corresponding {X}, [Y], and (Z) site (Table 3.2.4 to 3.2.6). The U values are as follows, for SAR-1 in the {X} site: 0.449(1), [Y] site: 0.186(8), and (Z) site:

0.295(2) Å2; for SAR-2 in the {X} site: 0.444(9), [Y] site: 0.223(6), and (Z) site: 0.296(1) Å2; for

STZ-1 in the {X} site: 0.486(9), [Y] site: 0.238(6), and (Z) site: 0.340(1) Å2; for JTC-1 in the

{X} site: 0.469(9), [Y] site: 0.259(5), and (Z) site: 0.363(1) Å2; and for FIN-1 in the {X} site:

2 0.454(1), [Y] site: 0.214(7), and (Z) site: 0.344(2) Å . Additionally, the UO, for SAR-1, SAR-2,

STZ-1, JTC-1, and FIN-1 are as follows: 0.831(2), 0.841(2), 0.924(1), 0.862(2), and 0.892(2) Å2, respectively.

In the single-phase refinements, U values are as follows, for SAR-1s in the {X} site:

0.437(1), [Y] site: 0.227(8), and (Z) site: 0.371(2) Å2; for SAR-2s in the {X} site: 0.435(1), [Y] site: 0.196(7), and (Z) site: 0.287(2) Å2; for STZ-3s in the {X} site: 0.406(1), [Y] site: 0.196(9), and (Z) site: 0.360(2) Å2; for JTC-4s in the {X} site: 0.493(2), [Y] site: 0.267(8), and (Z) site:

0.365(2) Å2; for JTC*-5s in the {X} site: 0.4762(3), [Y] site: 0.2562(3), and (Z) site: 0.2362(3)

Å2; and for FIN-6s in the {X} site: 0.482(4), [Y] site: 0.262(4), and (Z) site: 0.242(4) Å2.

Additionally, the UO, for SAR-1s, SAR-2s, STZ-3s, JTC-4s, JTC*-5s, and FIN-6s are as follows:

0.897(2), 0.851(2), 0.909(1), 0.843(2), 0.4362(3), and 0.442(4) Å2, respectively.

The general trend in U values is consistent for all six uvarovites studied in each corresponding site, such that UO >UX >UY >UZ. This pattern also holds true for all single-phase refinements. In contrast, Wildner and Andrut (2001) analysis on six birefringent uvarovites display a slightly different relationship in values; demonstrated by UX >UO >UY >UZ. Their crystal structure refinement involved reducing the cubic symmetry of Uv with space group Ia3d

103 to triclinic and by using a different space group of I1, may account for the observed differences in U. Likewise, Righter et al (2011) also possess a contrasting relationship in U values compared to this study, with an observed trend of UO >UY >UZ >UX. They performed crystal structure refinements based on Cr3+, Al3+, and Ti4+ all occupying the octahedral [Y] site, which could explain for the observed difference from this study.

3.2.9 Bond Distances

Selected interatomic bond distances for all Uv samples are summarized in Table 3.2.8.

The average , Y-O, and Z-O for each multiple phase are as follows: SAR-1a: =

2.4149, Cr-O = 1.9702(2), and Si-O = 1.6604(2) Å; SAR-1b: = 2.4225, Cr-O =

1.997(6), and Si-O = 1.605(5) Å; SAR-1c: = 2.4196, Cr-O = 1.9562(2), and Si-O =

1.6292(2) Å; SAR-2a: = 2.4220, Cr-O = 1.9752(7), and Si-O = 1.6471(7) Å; SAR-2b:

= 2.4455, Cr-O = 2.056(9), and Si-O = 1.585(8) Å; STZ-3a: = 2.4177, Cr-O =

1.9648(6), and Si-O = 1.6683(6) Å; STZ-3b: = 2.4177, Cr-O = 1.9756(2), and Si-O =

1.6547(3) Å; JTC-4a: = 2.4283, Cr-O = 2.0140(3) and Si-O = 1.6498(3) Å; JTC-4b:

= 2.4311, Cr-O = 2.0156(8), and Si-O = 1.6451(8) Å; FIN-6a: = 2.4166, Cr-O

= 1.9772(7), and Si-O = 1.6419(7) Å; FIN-6b: = 2.4070, Cr-O = 1.9848(1), and Si-O =

1.668(9) Å; FIN-6c: = 2.3920, Cr-O = 2.235(3), and Si-O = 1.708(3) Å; FIN-6d:

O> = 2.4140, Cr-O = 2.029(1), and Si-O = 1.586(9) Å. Additionally, the values obtained in single-phase refinement bond distances are reflective and comparingly similar to the dominant refinement phase (Table 3.2.8).

Uvarovite bond distances in literature were obtained from the following studies: Sawada

(1999) Ural Mountains CCG sample, Novak and Gibbs (1971) Uv from Washington, California,

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Wildner and Andrut’s (2001) six birefringent Uv from the Urals, Andrut and Wildner’s (2002) synthetic Uvasyn-22, and lastly Carda et al. (1994) synthetic Uv samples. In addition, bond distances from both near end-member grossular and andradite samples from Antao (2013) were used to show the bond length trends as a function of the a unit-cell parameter within the ugrandite end-members. Merli et al. (1995) examined the structural constraints on chemical variability of natural garnet and determined the largest variations of each bond length in the X,

Y, and Z sites to be a result from the substitution of cations at each particular site. Furthermore,

Merli et al. (1995) reported a linear relationship between a unit-cell parameters and corresponding {X}, [Y], and (Z) site bond distances derived from chemical substitutions from edge sharing sites.

Figures 3.3.1 and 3.3.2 illustrates the variations in bond length of each site with respect to the a unit-cell parameter. Bond length data of all samples fall within range between Grs and Adr data as is expected. The trend line in each graph takes into account all samples with the exception of FIN-6b, FIN-6c, FIN-6d, SAR-1b, and SAR-2b phases, since these minor phases show large uncertainty. In addition, synthetic Uv data from literature was used to show the variable ranges of bond distances but are not included into the trend line fit because all samples in this study are of natural uvarovite occurrences. A good linear relationship is observed between distances with respect to a unit-cell parameters, as shown by R² = 0.88681

(Figure 3.3.1a). In the dodecahedral {X} site there are two unique sets of X-O distances: X-O and X’-O. Ca2+ mostly occupies the {X} site, where X-O ranges from 2.138(3) Å in FIN-6c to

2.427(8) Å in SAR-2b. Correspondingly, X’-O has a range between 2.4401(2) Å in SAR-1a to

2.647(2) Å in FIN-6a (Table 3.2.8). The average X-O bond length is 0.1660 Å shorter than that of the length of X’-O. Accordingly, the smallest and largest differences between the two sets of

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X-O distances are 0.0370 Å in SAR-2b and 0.5100 Å in FIN-6c, respectively. All samples studied contain X-O and X’-O distances that fall within range and are consistent with literature values for uvarovite reported by Wildner and Andrut (2001), Novak and Gibbs (1971), Sawada

(1999), and Carda et al. (1994). The smallest distance, which is the average between the two sets of X-O distances, was found in FIN-6c with 2.3920 Å, whereas the largest distance was reported in SAR-2b with 2.4455 Å. However, low weight percents of these minor phases cause larger uncertainty and less accuracy, and is therefore not a good representation of the general trends in the structural analysis of the samples studied.

Y-O distances range from 1.948(1) Å in FIN-6B to 2.235(3) Å in FIN-6c (Table 3.2.8).

SAR-1, STZ-1, and JTC-1 show similar Y-O distances across each of their respective phases.

Instead, SAR-2 and FIN-1 contain Y-O distances in their minor phases that vary differently to the dominant phase. Increased Cr3+ and/or Fe3+ substitution for Al3+ occurs when Ca2+ is near full occupancy of the [X] site, causing an increase in the bond length (Merli et al 1995).

Also, an increased level of chromium content also expands the octahedral sites of the crystal structure with the replacement of Al3+ by Cr3+ cations (Wildner and Andrut 2001). Since JTC-1 shows significant substitution between Cr3+ and Fe3+ on the Y site and comprises of a Uv-Adr solid solution, the Cr/Fe-O distance is larger than all of the samples studied with a bond distance of 2.0140(3) Å in JTC-4a and 2.0156(8) Å in JTC-4b. Figure 3.3.1b displays a clear linear relationship between Y-O bond distances with increasing a unit-cell parameters as shown by R²

= 0.98169. FIN-6c (green triangle) have Y-O bond distances similar to that of the synthetic Uv-

Grs solid solution samples from Carda et al. (1994), meanwhile the remaining Uv samples are consistent with literature data.

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Z-O bond lengths range from 1.585(8) Å in SAR-2b to 1.708(3) Å in FIN-6c (Table

3.2.8). As previously stated, SAR-2b and FIN-6c are minor phases that are not used in the trend line fit, but the remaining Z-O bond lengths of the other phases comprise of intermediate values.

Figure 3.3.2a displays the least correlation when comparing changes in a unit-cell parameters with Z-O bond distances resulting in scattered Uv phases displaying no clear pattern, as shown by the low R² = 0.10334. D-O, is the average distance of the four-coordinated O atoms, and is obtained using the following formula: {(Z-O) + {Y-O) + (X-O) + (X’-O)}/4. An excellent correlation is observed between the D-O bond distances with increasing a unit-cell parameters

(Figure 3.3.2.b) of R² = 0.97303. All Uv phases studied including minor weight percent phases follow a gradual linear increase with values in between Grs to Adr end-members, excluding FIN-

6c. In addition, the synthetic Uv D-O bond length values from literature also exhibit a linear progression with the overall trend line.

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2.70 SAR-1 = 0.1272x + 0.8986 2.65 SAR-2 R² = 0.88681 STZ-1

2.60 JTC-1 JTC-1* 2.55 FIN-1 Literature

O> (Å) O> 2.50 Adr − Grs 2.45 Synthetic

2.35 = 0.4437x - 3.332 R² = 0.98169 2.25

2.15 O >(Å) O

− 2.05

a (Å) Figure 3.3.1. Relationship between a. ; Ca as the dominant {X} site atom and b. Y-O; Cr as the dominant [Y] site atom, both with respect to the a cell parameter (Å). Trend lines are fit to all of the samples studied along with literature data with the exception of the synthetic Uv samples from literature and excluding Uv phases: FIN-6b, c, d, SAR-1b, and SAR-2b. Grs data is taken from Antao (2013) and Adr data from Antao (2013). The remaining literature data are Uv from: Novak and Gibbs (1971), Carda et al. (1994), Sawada (1999), Wildner and Andrut (2001), and Andrut and Wildner (2002).

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1.90 SAR-1 = 0.1765x - 0.4582 SAR-2 R² = 0.10334 1.85 STZ-1 JTC-1

1.80 JTC-1* FIN-1 1.75 Literature Adr

O> (Å) O> 1.70 Grs

− Synthetic Grs

2.35 = 0.1743x + 0.0309 2.30 R² = 0.97303

2.25

2.20 O> (Å) O> − 2.15 Adr

2.10 Grs b 2.05 11.82 11.86 11.90 11.94 11.98 12.02 12.06 12.10 a (Å) Figure 3.3.2. Relationship between a. Z-O; Si as the dominant (Z) site atom and b. ; the average distance for the O atom, all with respect to the a cell parameter (Å). Trend lines are fit to all of the samples studied along with literature data with the exception of the synthetic Uv samples from literature and excluding Uv phases: FIN-6b, c, d, SAR-1b, and SAR-2b. Grs data is taken from Antao (2013) and Adr data from Antao (2013). The remaining literature data are Uv from: Novak and Gibbs (1971), Carda et al. (1994), Sawada (1999), Wildner and Andrut (2001), and Andrut and Wildner (2002).

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Table 3.2.8. Selected interatomic bond distances (Å) for five uvarovite garnet samples in this study 1. Sarany, Urals, Russia (SAR-1) 2. Sarany, Urals, Russia (SAR-2) Multi-Phase Single Multi-Phase Single

SAR-1a SAR-1b SAR-1c SAR-1s SAR-2a SAR-2b SAR-2s Z-O x4 1.6604(2) 1.605(5) 1.6292(2) 1.6420(6) 1.6471(7) 1.585(8) 1.6452(6)

Y-O x6 1.9702(2) 1.997(6) 1.9562(2) 1.9644(6) 1.9752(7) 2.056(9) 1.9778(6)

X-O x4 2.3896(2) 2.352(5) 2.2777(2) 2.3416(6) 2.3458(6) 2.427(8) 2.3505(5)

X’-O x4 2.4401(2) 2.493(5) 2.5615(3) 2.4926(6) 2.4981(6) 2.464(8) 2.4957(6)

[8] 2.4149 2.4225 2.4196 2.4171 2.4220 2.4455 2.4231

a [4] 2.1151 2.1118 2.1061 2.1102 2.1166 2.1330 2.1173 Y-O-Z x1 133.26(1) 134.95(3) 136.64(2) 134.98(4) 134.68(4) 133.2(5) 134.635(3) 3. Switzerland (STZ-1) 4. Jacksonville, Tuolumne County, California (JTC-1)

Multi-Phase Single Multi-Phase (Dark) Single (Dark) Single (Light)

STZ-3a STZ-3b STZ-3s JTC-4a JTC-4b JTC-4s JTC-5s

Z-O x4 1.6483(6) 1.6547(3) 1.6499(7) 1.6498(3) 1.6451(8) 1.6463(9) 1.6450(6) Y-O x6 1.9648(6) 1.9756(2) 1.9650(7) 2.0140(3) 2.0156(8) 2.0152(8) 2.0197(6)

X-O x4 2.3390(6) 2.3542(2) 2.3415(6) 2.3511(2) 2.3629(7) 2.3610(8) 2.3606(6)

X’-O x4 2.4963(6) 2.4812(2) 2.4932(6) 2.5054(3) 2.4992(7) 2.5003(8) 2.4999(6)

[8] 2.4177 2.4177 2.4174 2.4283 2.4311 2.4307 2.4303

a [4] 2.1121 2.1164 2.1124 2.1301 2.1307 2.1307 2.1313

Y-O-Z x1 134.864(4) 134.05(1) 134.75(4) 133.49(2) 133.54(4) 133.53(5) 133.375(3)

a = {(Z-O) + {Y-O) + (X-O) + (X’-O)}/4, which is the average distance from the four-coordinated O atom.

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Table 3.2.8. (Continuation) Selected interatomic bond distances (Å) for five uvarovite garnet samples in this study 5. Outokumpu, Finland (FIN-1) Multi-Phase Single

FIN-6a FIN-6b FIN-6c FIN-6d FIN-6s

Z-O x4 1.6419(7) 1.668(9) 1.708(3) 1.586(9) 1.6452(7) Y-O x6 1.9772(7) 1.948(1) 2.235(3) 2.029(1) 1.9757(7) X-O x4 2.3338(7) 2.321(8) 2.138(3) 2.325(9) 2.3339(7) X-O x4 2.4994(7) 2.493(8) 2.647(2) 2.503(8) 2.4962(7) [8] 2.4166 2.4070 2.3920 2.4140 2.4151 a [4] 2.1131 2.1075 2.1813 2.1108 2.1128 Y-O-Z x1 134.59(4) 134.5(5) 115.5(1) 134.1(5) 134.45(4) a = {(Z-O) + {Y-O) + (X-O) + (X’-O)}/4, which is the average distance from the four- coordinated O atom.

3.3 Evaluation of Birefringence in Uvarovite Garnet

Numerous investigations in the last century were performed to determine the origin of optical anisotropy in many garnet end-member species. The most widely accepted causes to birefringence in garnets are attributed to: distribution of hydrous components (Allen and Buseck

1988; Andrut et al. 2001), twinning (Ingerson and Barsdale 1943), cation ordering on the {X} and [Y] sites leading to a reduction of lower symmetry (Allen and Buseck 1988; Wildner and

Andrut 2001; Shtukenberg et al. 2005), and strain (Hofmeister et al. 1998; by Arai and Akizawa

2014).

Hydrogen atoms can enter the garnet crystal structure and substitute for Si4+ in the tetrahedral (Z) site, through a process known as the hydrogarnet substitution. The 4H4+

4+ 4- 4- substitutes Si producing (O4H4) in place of (SiO4) (Allen and Buseck 1988). The presence of

OH- groups within the uvarovite structure may be possible considering the ugrandite series are

111 known to be able to contain low levels of water content, up to 15% in hydrogrossular and hydroandradite varieties (Pal and Das 2010). However, Uv is typically more anhydrous than hydrous, as confirmed in Tables 3.2.2, 3.2.4, and 3.2.6. The sof values obtained by both EMPA and HRPXRD are near full occupancy by Si4+ in the (Z) site, leaving no vacancy for OH- groups.

Furthermore, annealing experiments by Allen and Buseck (1988) and Andrut et al. (2001) of their Grs and Uv samples, respectively, revealed loss of hydrous groups. Although, birefringence still remained in their samples, indicating that hydrous components are not the sole cause of optical anisotropy in uvarovite garnet.

Ingerson and Barsdale (1943) hypothesized large-scale twinning to be the cause of birefringence in garnets. They conducted annealing experiments to observe when the temperature of birefringent garnet reverts back into cubic symmetry, resulting in the loss of optical anisotropy. Near melting temperatures had decreased the birefringence but the twinning they observed was still preserved, which remained visible. As a result, Ingerson and Barsdale

(1943) concluded that optical anisotropy was derived from the fine polysynthetic twinning.

However, numerous studies regarding birefringent garnets display no signs of twinning (Novak and Gibbs 1971; Allen and Buseck 1988). Furthermore, uvarovite crystals used in this study were weakly birefringent but many did not exhibit any signs of twinning, therefore twinning cannot cause optical anisotropy in garnets. If twinning textures were the source of optical anisotropy, all optically birefringent samples should exhibit some form of twinning.

The most widely accepted cause of birefringence in garnets is cation ordering; occurring in the octahedral [Y] site most commonly between Al3+, Cr3+, and Fe3+ in ugrandite garnets

(Shtukenberg et al. 2005). In contrast, cation ordering for pyralspite garnets arises in the dodecahedral {X} site between Mn 2+, Mg2+, and Fe2+ (Allen and Buseck 1988). Octahedral [Y]

112 site cations control the growth face of the atomic structure by splitting an ordered sequence into two symmetrically but distinct [Y] sites producing preferential site selection between Al3+, Cr3+, and Fe3+ cations (Shtukenberg et al. 2005). Although, this does not apply to near or pure end- member garnets considering there is only one dominant [Y] site cation fully occupying the site

(Antao 2013). The ordered arrangement of split octahedral cations could cause a reduction in symmetry to orthorhombic, monoclinic or triclinic systems (Shtukenberg et al. 2005). In general, the a unit-cell parameter of uvarovite is reported to be 11.988(1) Å with angles, α = β =

γ = 90° (Novak and Gibbs 1971). Wildner and Andrut (2001) reported the birefringence of their

Uv sample, Sar-desy, to be a result from a reduction in symmetry, yet, their reported values show little variation between the cell dimensions and are as follows: a = 11.968(1) Å, b = 11.967(1) Å, c = 11.968(1) Å, and α = 90.01(1)°, β = 90.15(1)°, and γ = 90.01(1)°. Similarly, all of their other five Uv samples yield values that are comparable and consistent to Sar-desy displaying no obvious discrepancies from cubic cell parameters. The very subtle differences in cell dimensions are within the limits of error, such that it essentially remains unchanged and cannot easily explain a reduction from cubic symmetry. Crystal structure refinements in different symmetry space groups do not indicate that the refinement is correct (Akizuki 1984).

Examining the EMPA results of each sample, since all Uv specimens are solid solutions and are essentially not near end-member uvarovite, there can be a possibility of Cr3+- Al3+ ordering on the octahedral [Y] site in SAR-1, SAR-2, SKR-1, and FIN-1. Additionally, there could be Cr3+/ Fe3+ - Al3+ ordering within STZ-1 and Cr3+- Fe3+ ordering in JTC-1. However, examining the HRPXRD traces, there was no deviation from cubic symmetry in all diffraction traces, such that all peaks were indexed and show no sign of any additional unindexed peaks, indicating no symmetry violations that could suggest cation ordering or lower symmetry

113 reduction. HRPXRD refinement using the space group Ia3d produces a unique X-ray diffraction trace that is characteristic to the cubic crystal system and visually is different than refining using lower symmetry crystal systems, which would instead result in more observed peaks. The evidence supported in this thesis suggests that cation ordering or a reduction to lower symmetry does not explain or cause the birefringence in uvarovite and also to the larger garnet group of minerals.

Another widely accepted cause of birefringence is attributed to strain. A study by

Hofmeister et al. (1998) analyzed 48 garnets exhibiting low birefringence as well as undulatory extinction and proposed that an internal process was the source for the origin of optical anisotropy in garnets. Specifically, they stated the internal strain within the crystal structure between a mismatch in sizes of dodecahedral {X} site cations, of the large Ca2+ and the small

Mg2+ cations cause an expansion as more Ca2+ enter the {X} site. Correspondingly, they concluded that strain is independent and does not affect the crystal structure of birefringent garnets, indicating that the crystal symmetry remains cubic, which resultantly was maintained for all of their 48 garnet samples. Furthermore, powder XRD data of optically anisotropic garnets display diffraction patterns closely related to cubic crystal systems, containing less peaks than lower symmetry systems.

Using EMPA and Synchrotron HRPXRD techniques, results identified EMPA phases of heterogeneous compositions of all uvarovite samples to have analogous HRPXRD phases. The miniscule size differences in the a unit cell parameters between multiple uvarovite phases causes structural mismatch at phase boundaries, resulting in strain that gives rise to the anomalous birefringence in uvarovite garnet, and possibly to other end-member birefringent species. These additional Uv phases occur as fine scale intergrowths of variable weight percentages ranging

114 from very minor to considerable proportions mixed in with the dominant phase. Single crystal

X-ray diffraction (SXTL) techniques cannot detect the existence of additional minor phases and therefore only collects information reflective of the dominant phase (Antao 2008). In addition, the resolution of HRPXRD is superior to that of SXTL methods as well as EMPA due to the ability of the HRPXRD technique to be able to distinguish between phases of fine scale intergrowths (Antao 2008). Similar results to the ones in this thesis are presented in other birefringent garnets studies analyzed by HRPXRD (Antao 2013; Antao and Klincker 2013,

Antao et al. 2015).

As previously stated the degree of birefringence is measured by the difference in a unit- cell parameters between multiple cubic phases, Δa, (Table 3.2.1, 3.2.3, and 3.2.5; Kitamura and

Komatsu 1978). Furthermore, Δa can be visually seen as the coloured vertical lines representing different phases, located beneath the diffraction peak profiles and above the difference curves of each XRD trace in this study. Single-phase diffraction patterns are most representative of sharp and symmetry peak profiles across a selected 2θ range as seen in JTC*-5s (Figure 3.2.5). Multi- phase diffraction patterns are most indicative of profiles that exhibit broadening effects and asymmetrical peaks throughout the trace caused by the addition of the secondary phase(s) as observed in SAR-1, SAR-2, STZ-1, JTC-1, and in FIN-1. The presence of these additional phases contains different sizes of a unit-cell parameters and the interaction between the polyhedral bonds of these structural intergrowths induces strain causing the optical anisotropy that is observed in uvarovite. Most previous studies report the observed birefringence to be the result of a symmetry reduction or the product of cation ordering, however, strain further confirms the cubic nature of uvarovite as it shows no deviation from cubic symmetry.

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CHAPTER 4: CONCLUSION

This thesis investigated the crystal chemistry and structure of birefringent cubic uvarovite garnet from Sarany, Urals, Russia; Zermatt, Switzerland; Outokumpu, Finland; and Jacksonville

Tuolumne County, California to determine the cause of optical anisotropy. All samples studied show distinct birefringence with many crystals exhibiting additional anisotropic features, such as: oscillatory zoning, bow-tie structures, and well-defined extinction positions. For over a century, geoscientists observed the inconsistency of optical microscopy in several garnet group end-members displaying optical anisotropy, while X-ray diffraction methods show no divergence from cubic symmetry. Although, many previous studies did not have the opportunity to analyze their samples using Synchrotron HRPXRD, where additional phases of variable weight percents with slightly different compositions are possible to detect and analyze.

HRPXRD data obtained has identified the existence of additional multiple phase intergrowths in each corresponding uvarovite sample except JTC*-5s. The Rietveld structure refinements have visually produced powder diffraction traces that are indexed to be cubic, with minor variability in the shape and intensity of peaks, such as peak asymmetry and peak broadening effects, influenced by the existence of secondary cubic phases of Uv. Past investigations have proposed the lowering of cubic symmetry into several other crystal systems.

However, a reduction of symmetry into triclinic or orthorhombic crystal systems would produce very different diffraction patterns resulting in the appearance of additional unindexed peaks, which there was no such evidence in this study. In addition, the calculated and observed peak profiles are consistent throughout each diffraction pattern, located in the same position with very minute changes in their difference curves further indicating the high accuracy and cubic nature of

116 the uvarovite samples studied. The small structural changes in a unit-cell parameters between the multiple phases in each sample, is represented by Δa, and ultimately causes the observed birefringence in uvarovite garnet, as attributed by strain derived by lattice mismatch.

Previous studies in the last century have used spectroscopic, EMPA, conventional powder, and single crystal XRD techniques to evaluate the birefringence phenomenon in several natural and synthetic garnets species. These techniques do not have the ability to detect the existence of multiple phases at such a fine scale. Additionally, the SXTL method identifies and analyzes the structural data for only the dominant phase present, and does not detect the possible existence of secondary fine-scale phases. In studies involving the analysis of atoms and crystal structure of materials, the resolution of the analytical technique used is very important to consider. The HRPXRD technique provides data of superior quality and accuracy to that of

SXTL and EMPA, and enables us to capture structural information on all phases present in any crystalline sample, as evident in the uvarovite samples in this thesis. The high resolution of this technique has expanded the field of crystal structure studies on materials and minerals and provided clarity and shed light on the anomalous birefringence phenomenon in garnets that revolved around a century of extensive studies. The results from this thesis are similar to other birefringent garnets analyzed by HRPXRD (Antao 2013; Antao and Klincker 2013) and recommendations for future work should be completed to evaluate not only the previously studied garnets, but also includes the diverse and rarer end-member species.

117

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124

APPENDIX A

Electron Microprobe Analysis (EMPA)

EMPA data from six uvarovite samples were analyzed using an Excel spreadsheet created by

Locock (2008) to calculate atom per formula units (apfu) and the molar proportions of garnet end-members, assuming eight cations and twelve oxygen atoms.

125

Table A1.1. EMPA of seven analyzed points of SAR-1 from Sarany, Urals, Russia Oxide (wt. %) 1 2 3 4 5 6 7 1.3.2 1.3.1 1.3.5 1.3.6 1.3.7 1.3.4 1.3.3 SiO2 38.48 38.11 37.87 38.42 38.09 38.01 37.22 TiO2 0.20 0.19 0.20 0.20 0.23 0.21 0.18 Al2O3 12.48 12.15 11.02 10.83 9.98 9.15 8.47 Cr2O3 12.58 12.67 14.54 14.65 16.11 17.39 18.01 Fe2O3 / calc 0.97 1.25 0.83 0.94 0.61 0.61 0.66 MnO 0.05 0.09 0.08 0.08 0.09 0.05 0.06 MgO 0.00 0.00 0.02 0.00 0.03 0.01 0.01 CaO 34.75 35.48 35.18 34.75 34.85 34.38 34.82 Σ (calc) 99.50 99.93 99.73 99.86 100.00 99.82 99.43 Recalculated (wt. %)

final Fe2O3 0.97 1.25 0.83 0.94 0.61 0.61 0.66 final MnO 0.05 0.09 0.08 0.08 0.09 0.05 0.06 Σ 99.50 99.93 99.73 99.86 100.00 99.82 99.43 Cations for 12 O atoms

Ca 2.941 2.993 2.988 2.951 2.967 2.945 3.001 Mn2+ 0.003 0.006 0.005 0.005 0.006 0.003 0.004 Mg 0.000 0.000 0.002 0.000 0.004 0.002 0.000 ΣX 2.944 2.999 2.995 2.957 2.977 2.950 3.005 Cr 0.786 0.789 0.911 0.918 1.012 1.099 1.145 Al 1.161 1.127 1.030 1.012 0.934 0.862 0.798 Fe3+ 0.058 0.074 0.050 0.056 0.036 0.037 0.040 Ti 0.012 0.011 0.012 0.012 0.014 0.013 0.011 Mg 0.000 0.000 0.000 0.000 0.000 0.000 0.001 Si 0.039 0.000 0.002 0.045 0.026 0.038 0.000 ΣY 2.056 2.001 2.005 2.043 2.023 2.050 1.995 Si 3.000 3.000 3.000 3.000 3.000 3.000 2.994 Al 0.000 0.000 0.000 0.000 0.000 0.000 0.006 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 0.982 1.000 0.999 0.986 0.992 0.983 1.002 EMPA Y sof Cr 0.755 0.745 0.767 0.782 0.793 0.820 0.816 EMPA Z sof 1.000 1.000 1.000 1.000 1.000 1.000 1.000 F(000) 137 138 139 139 140 140 141 End-Member mole %

Uvarovite 39 39 46 46 51 55 57 Grossular 58 56 51 50 46 43 40 Andradite 1 4 2 2 2 0 2 Remainder 2 1 0 1 1 2 0 Σ 100 100 100 100 100 100 100 Quality Index Fair Good Good Fair Good Fair Exc. 2+ 3+ Composition: Phase-1 (pts.1-2): {Ca2.96Mn 0.01}Σ2.97[Al1.14Cr0.79Fe 0.07Si0.02Ti0.01]Σ2.03(Si3.00)O12; 2+ 3+ Uv39Grs57Adr3; Phase-2 (pts. 3-5): {Ca2.97Mn 0.01}Σ2.98[Al0.99 Cr0.94Fe 0.05Si0.03Ti0.01]Σ2.02(Si3.00)O12; 3+ Uv48Grs49Adr2; and Phase-3 (pts. 6-7): {Ca2.97}Σ2.97[Cr1.12Al0.83 Fe 0.04Si0.02Ti0.01]Σ2.02(Si3.00)O12; Uv56Grs42Adr1

126

Table A1.2. EMPA data of four analyzed points of SAR-2 from Sarany, Urals, Russia Oxide (wt. %) 1 2 3 4 2.7.5 2.7.10 2.7.4 2.7.3 SiO2 35.48 35.13 35.36 35.30 TiO2 1.85 1.66 1.34 0.99 Al2O3 6.39 5.68 6.04 6.02 Cr2O3 17.65 18.66 18.71 19.18 V2O3 0.39 0.51 0.30 0.22 Fe2O3 / calc 0.84 1.09 0.88 0.92 MnO 0.01 0.06 0.08 0.07 MgO 0.05 0.07 0.05 0.06 CaO 34.28 34.32 34.02 33.83 Σ (calc) 96.95 97.18 96.78 96.59 Recalculated (wt. %)

final Fe2O3 0.84 1.09 0.88 0.92 final MnO 0.01 0.06 0.08 0.07 Σ 96.95 97.18 96.78 96.59 Cations for 12 O atoms

Ca 3.057 3.065 3.045 3.034 Mn2+ 0.001 0.004 0.006 0.005 ΣX 3.058 3.069 3.050 3.039 Cr 1.161 1.230 1.236 1.269 Al 0.580 0.486 0.548 0.549 Ti 0.116 0.104 0.084 0.062 Fe3+ 0.053 0.068 0.055 0.058 V 0.026 0.034 0.020 0.015 Mg 0.006 0.009 0.006 0.007 ΣY 1.942 1.931 1.950 1.961 Si 2.953 2.928 2.954 2.955 Al 0.047 0.072 0.046 0.045 ΣZ 3.000 3.000 3.000 3.000 EMPA X sof 1.019 1.023 1.017 1.013 EMPA Y sof Cr 0.834 0.850 0.846 0.852 EMPA Z sof 0.999 0.998 0.999 0.999 F(000) 143 144 144 144 End-Member mole %

Uvarovite 58 61 62 63 Grossular 29 24 27 27 Andradite 3 3 3 3 Schorlomite-Al 2 4 2 2 Goldmanite 1 2 1 1 Morimotoite-Mg 1 1 1 1 Remainder 6 5 4 2 Σ 100 100 100 100 Quality Index Poor Poor Poor Poor Composition of SAR-2: Phase-1 (pt.1): {Ca3.06}[Cr1.16Al0.58Ti0.12 3+ Fe 0.05V0.03Mg0.01]Σ1.94(Si2.95Al0.05)Σ3.00O12; Uv58Grs29Adr3 and Phase-2 2+ 3+ (pts.2-4): {Ca3.04Mn 0.01}Σ3.05 [Cr1.25Al0.53Ti0.8Fe 0.06V0.02Mg0.01]Σ1.95 (Si2.95Al0.05)Σ3.00O12; Uv62Grs26Adr3

127

Table A1.3. EMPA data of seven analyzed points of SKR-1 from Saranovsky Mine, Urals, Russia Oxide (wt. %) 1 2 3 4 5 6 7 2.8.3 2.8.4 2.8.2 2.8.7 2.8.6 2.8.1 2.8.5 SiO2 33.84 33.80 34.93 32.62 33.30 35.07 32.73 TiO2 1.87 1.94 1.84 1.84 1.89 1.49 1.65 Al2O3 6.53 6.54 6.26 6.23 6.07 5.49 4.87 Cr2O3 17.37 17.53 17.81 17.66 17.77 18.85 19.70 V2O3 0.35 0.34 0.39 0.32 0.29 0.42 0.29 Fe2O3 / calc 0.98 0.83 1.08 0.96 0.93 1.18 0.93 MnO 0.07 0.07 0.08 0.04 0.04 0.04 0.05 MgO 0.05 0.06 0.06 0.06 0.02 0.05 0.04 CaO 33.70 33.76 33.84 33.54 33.48 34.06 33.13 Σ (calc) 94.76 94.86 96.27 93.27 93.80 96.65 93.38 Recalculated (wt. %)

final Fe2O3 0.98 0.83 1.08 0.96 0.93 1.18 0.93 final MnO 0.07 0.07 0.08 0.04 0.04 0.04 0.05 Σ 94.77 94.87 96.28 93.26 93.80 96.65 93.38 Cations for 12 O atoms

Ca 3.075 3.078 3.043 3.113 3.093 3.061 3.093 Mn2+ 0.005 0.005 0.006 0.003 0.003 0.003 0.004 ΣX 3.080 3.082 3.049 3.117 3.095 3.064 3.096 Cr 1.170 1.179 1.182 1.209 1.211 1.250 1.357 Al 0.537 0.531 0.552 0.462 0.488 0.484 0.352 Ti 0.120 0.124 0.116 0.120 0.123 0.094 0.108 Fe3+ 0.063 0.053 0.068 0.063 0.061 0.074 0.061 V 0.024 0.023 0.026 0.022 0.020 0.028 0.020 Mg 0.007 0.007 0.007 0.007 0.002 0.006 0.005 ΣY 1.920 1.918 1.951 1.883 1.905 1.936 1.904 Si 2.882 2.876 2.932 2.826 2.871 2.941 2.852 Al 0.118 0.124 0.068 0.174 0.129 0.059 0.148 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 1.027 1.028 1.017 1.039 1.032 1.021 1.032 EMPA Y sof Cr 0.833 0.832 0.845 0.831 0.837 0.854 0.867 EMPA Z sof 0.997 0.997 0.998 0.996 0.997 0.999 0.996 F(000) 143 143 143 144 144 144 145 End-Member mole %

Uvarovite 58 59 59 60 61 62 68 Grossular 27 26 27 23 24 24 17 Schorlomite-Al 6 6 3 6 6 3 5 Andradite 3 3 3 3 3 4 3 Goldmanite 1 1 1 1 1 1 1 Morimotoite-Mg 0 0 1 0 0 1 0 Remainder 4 4 5 6 5 5 5 Σ 100 100 100 100 100 100 100 Quality Index Poor Poor Poor Poor Poor Poor Poor 3+ Composition: Phase-1 (pts.1-6): {Ca3.08}[Cr1.20Al0.51Ti0.12Fe 0.06V0.02Mg0.01]Σ1.92(Si2.89Al0.12) 3+ Σ3.00O12; Uv60Grs25Sch5Adr3 and Phase-2 (pt.7): {Ca3.09}Σ3.09 [Cr1.36Al0.35Ti0.11Fe 0.06V0.02 Mg0.01]Σ1.90(Si2.86Al0.15)Σ3.00O12; Uv68Grs17Sch5Adr3

128

Table A1.4. EMPA of 14 analyzed points of STZ-1 from Zermatt, Switzerland Oxide (wt. %) 1 2 3 4 5 6 7 1Q.1.2 1Q.1.1 1Q.1.4 1Q.4.2 1Q.1.6 1Q.5.2 1Q.2.1

SiO2 38.01 37.33 37.98 37.28 37.81 37.17 37.32 TiO2 0.27 0.27 0.29 0.39 0.30 0.31 0.26 Al2O3 12.79 13.32 11.97 10.40 11.93 11.02 10.60 Cr2O3 3.82 4.86 6.53 6.58 6.76 7.65 8.19 Fe2O3 / calc 9.46 7.95 8.10 9.69 7.61 7.96 7.98 MnO 0.51 0.55 0.41 0.39 0.43 0.40 0.39 MgO 0.20 0.20 0.14 0.08 0.18 0.10 0.09 CaO 34.87 34.56 33.92 34.05 34.68 33.93 34.74 Σ (calc) 99.93 99.04 99.34 98.86 99.70 98.54 99.57 Recalculated (wt. %)

final Fe2O3 9.46 7.95 8.10 9.69 7.61 7.96 7.98 final MnO 0.51 0.55 0.41 0.39 0.43 0.40 0.39 Σ 99.93 99.04 99.34 98.86 99.70 98.54 99.57 Cations for 12 O atoms

Ca 2.944 2.937 2.894 2.940 2.944 2.929 2.973 Mn2+ 0.034 0.037 0.028 0.027 0.029 0.028 0.026 Mg 0.022 0.024 0.017 0.010 0.021 0.012 0.001 ΣX 3.000 2.998 2.938 2.977 2.995 2.969 3.000 Al 1.183 1.207 1.123 0.988 1.110 1.042 0.978 Fe3+ 0.561 0.474 0.485 0.588 0.454 0.483 0.480 Cr 0.238 0.305 0.411 0.419 0.424 0.487 0.517 Ti 0.016 0.016 0.017 0.024 0.018 0.019 0.016 Mg 0.002 0.000 0.000 0.000 0.000 0.000 0.010 Si 0.000 0.000 0.024 0.005 0.000 0.000 0.000 ΣY 2.000 2.002 2.062 2.023 2.005 2.031 2.000 Si 2.995 2.961 3.000 3.000 2.996 2.995 2.980 Al 0.005 0.039 0.000 0.000 0.004 0.005 0.020 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 1.000 0.999 0.980 0.993 0.998 0.990 1.002 EMPA Y sof Cr 0.751 0.744 0.788 0.808 0.767 0.796 0.793 EMPA Z sof 1.000 0.999 1.000 1.000 1.000 1.000 1.000 F(000) 138 138 139 140 139 140 140 End-Member mole %

Uvarovite 12 15 21 21 21 24 26 Grossular 57 58 55 48 54 51 48 Andradite 28 23 21 29 23 22 24 Spessartine 1 1 1 1 1 1 1 Pyrope 1 1 1 0 1 0 0 Schorlomite-Al 0 1 0 0 0 0 1 Remainder 0 1 2 1 0 1 0 Σ 100 100 100 100 100 100 100 Quality Index Sup Exc Poor Good Exc Good Sup 2+ 3+ Composition: Phase-1 (1-10): {Ca2.94Mn 0.03Mg0.01}Σ2.98[Al1.06Fe 0.50Cr0.44Ti0.02]Σ2.01(Si2.99Al0.01)Σ3.00O12; 2+ 3+ Uv22Grs51Adr24 and Phase-2 (pts.11-14): {Ca2.96Mn 0.02Mg0.01}Σ2.99[Cr0.87Al0.69Fe 0.43Ti0.01Si0.01]Σ2.01 (Si2.99Al0.01)Σ3.00O12; Uv43Grs34Adr21

129

Table A1.4. (Continuation) EMPA data of 14 analyzed points of STZ-1 from Zermatt, Switzerland Oxide (wt. %) 8 9 10 11 12 13 14 1Q.4.3 1Q.7.3 1Q.3.2 1Q.1.5 1Q.7.2 1Q.1.3 1Q.5.1

SiO2 37.21 37.18 37.20 36.81 36.78 37.34 36.77 TiO2 0.31 0.28 0.24 0.30 0.33 0.19 0.13 Al2O3 10.33 10.53 10.05 8.13 7.04 7.69 6.59 Cr2O3 8.14 8.22 8.38 11.54 13.19 13.48 15.73 Fe2O3 / calc 8.17 7.79 8.41 8.10 7.66 6.77 5.48 MnO 0.40 0.40 0.34 0.26 0.22 0.44 0.31 MgO 0.08 0.12 0.10 0.05 0.05 0.11 0.11 CaO 33.90 34.46 34.17 34.56 34.10 34.01 33.59 Σ (calc) 98.54 98.98 98.89 99.75 99.37 100.03 98.71 Recalculated (wt. %)

final Fe2O3 8.17 7.79 8.41 8.10 7.66 6.77 5.48 final MnO 0.40 0.40 0.34 0.26 0.22 0.44 0.31 Σ 98.54 98.98 98.89 99.75 99.37 100.03 98.71 Cations for 12 O atoms

Ca 2.936 2.966 2.952 2.987 2.973 2.937 2.950 Mn2+ 0.027 0.027 0.023 0.018 0.015 0.030 0.022 Mg 0.010 0.007 0.012 0.000 0.006 0.013 0.013 ΣX 2.973 3.000 2.987 3.005 2.994 2.980 2.985 Al 0.984 0.983 0.954 0.743 0.668 0.730 0.637 Fe3+ 0.497 0.471 0.510 0.492 0.469 0.410 0.338 Cr 0.520 0.522 0.534 0.736 0.849 0.859 1.019 Ti 0.019 0.017 0.015 0.018 0.020 0.012 0.008 Mg 0.000 0.007 0.000 0.006 0.000 0.000 0.000 Si 0.007 0.000 0.000 0.000 0.000 0.009 0.014 ΣY 2.027 2.000 2.013 1.995 2.006 2.020 2.015 Si 3.000 2.986 2.999 2.970 2.993 3.000 3.000 Al 0.000 0.014 0.001 0.030 0.007 0.000 0.000 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 0.992 1.001 0.996 1.003 0.999 0.994 0.995 EMPA Y sof Cr 0.806 0.792 0.809 0.845 0.868 0.857 0.873 EMPA Z sof 1.000 1.000 1.000 0.999 1.000 1.000 1.000 F(000) 140 140 141 143 144 143 144 End-Member mole %

Uvarovite 26 26 27 37 42 43 51 Grossular 48 48 47 37 33 35 31 Andradite 24 24 25 25 23 20 17 Spessartine 1 1 1 1 1 1 1 Pyrope 0 0 0 0 0 0 0 Schorlomite-Al 0 1 0 1 0 0 0 Remainder 1 0 0 1 0 1 1 Σ 100 100 100 100 100 100 100 Quality Index Good Sup Exc Exc Exc Good Good 2+ 3+ Composition: Phase-1 (1-10): {Ca2.94Mn 0.03Mg0.01}Σ2.98[Al1.06Fe 0.50Cr0.44Ti0.02]Σ2.01(Si2.99Al0.01)Σ3.00O12; 2+ 3+ Uv22Grs51Adr24 and Phase-2 (pts.11-14): {Ca2.96Mn 0.02Mg0.01}Σ2.99[Cr0.87Al0.69Fe 0.43Ti0.01Si0.01]Σ2.01 (Si2.99Al0.01)Σ3.00O12; Uv43Grs34Adr21

130

Table A1.5. EMPA data of 25 analyzed points of JTC-1 from Jacksonville, California Oxide (wt. %) 1 2 3 4 5 6 7 8 1.2.1 1.5.3 1.4.2 1.2.2 1.5.1 1.2.7 1.5.2 1.2.5 SiO2 36.31 34.15 35.98 36.02 35.47 35.81 35.62 35.70 TiO2 0.11 0.13 0.22 0.22 0.17 0.34 0.38 0.45 Al2O3 0.89 0.95 0.81 0.78 0.88 0.54 0.60 0.49 Cr2O3 0.28 0.63 0.66 0.67 0.70 1.52 1.66 2.27 V2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe2O3 / calc 30.06 29.09 29.62 29.68 29.59 29.10 29.00 28.07 MnO 0.03 0.02 0.03 0.04 0.05 0.03 0.07 0.03 MgO 0.04 0.05 0.01 0.02 0.00 0.06 0.04 0.04 CaO 32.62 32.80 32.82 32.76 33.36 32.98 32.98 32.84 Σ (calc) 100.34 97.82 100.15 100.19 100.22 100.38 100.35 99.89 Recalculated (wt. %) final Fe2O3 30.06 29.09 29.62 29.68 29.59 29.10 29.00 28.07 final MnO 0.03 0.02 0.03 0.04 0.05 0.03 0.07 0.03 Σ 100.34 97.82 100.15 100.19 100.22 100.38 100.35 99.89 Cations for 12 O atoms

Ca 2.933 3.023 2.958 2.952 3.002 2.968 2.969 2.969 Mg 0.005 0.000 0.001 0.003 0.000 0.008 0.005 0.005 Mn2+ 0.002 0.002 0.002 0.003 0.004 0.002 0.005 0.002 Na 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣX 2.940 3.025 2.961 2.957 3.006 2.977 2.979 2.976 Fe3+ 1.899 1.883 1.875 1.878 1.871 1.839 1.834 1.783 Cr 0.019 0.043 0.044 0.045 0.046 0.101 0.110 0.151 Al 0.088 0.035 0.080 0.077 0.066 0.053 0.052 0.049 Si 0.047 0.000 0.026 0.029 0.000 0.007 0.000 0.012 Ti 0.007 0.008 0.014 0.014 0.011 0.021 0.024 0.029 Mg 0.000 0.006 0.000 0.000 0.000 0.000 0.000 0.000 V 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣY 2.060 1.975 2.039 2.043 1.994 2.023 2.021 2.024 Si 3.000 2.938 3.000 3.000 2.979 3.000 2.993 3.000 Al 0.000 0.062 0.000 0.000 0.021 0.000 0.007 0.000 Fe3+ 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 0.980 1.008 0.987 0.986 1.002 0.992 0.993 0.992 EMPA Y sof Cr 1.079 1.056 1.073 1.075 1.059 1.073 1.074 1.071 EMPA Z sof 1.000 0.999 1.000 1.000 1.000 1.000 1.000 1.000 F(000) 153 153 153 153 153 153 153 153 End-Member mole %

Uvarovite 1 2 2 2 2 5 6 8 Andradite 93 94 92 92 93 92 91 89 Grossular 4 2 4 4 3 2 2 2 Schorlomite-Al 0 0 0 0 1 0 0 0 Remainder 2 2 1 1 0 1 1 1 Σ 100 100 100 100 100 100 100 100 Quality Index Fair Good Fair Fair Exc Good Exc Good 3+ Composition: Phase-1 (pts.1-19): {Ca2.98}[Fe 1.76Cr0.17Al0.05Ti0.02Si0.01]Σ2.01 (Si2.99Al0.01)Σ3.00O12; 2+ 3+ Uv9Adr88Grs2 and Phase-2 (pts. 20-25): {Ca2.99Mg0.01Mn 0.01}Σ3.01[Fe 1.29Cr0.61Al0.06Ti0.02Si0.01Mg0.01]Σ2.00 (Si2.99Al0.01)Σ3.00O12; Uv30Adr64Grs3

131

Table A1.5. (Continuation) EMPA data of 25 analyzed points of JTC-1 from Jacksonville, California Oxide (wt. %) 9 10 11 12 13 14 15 16 1.2.3 1.2.13 1.2.14 1.2.17 1.2.4 1.4.1 1.2.16 1.2.15 SiO2 35.77 35.40 36.00 36.05 35.37 34.83 35.79 36.16 TiO2 0.52 0.54 0.37 0.36 0.34 0.36 0.34 0.36 Al2O3 0.44 0.50 0.50 0.57 0.53 0.56 0.66 0.56 Cr2O3 2.35 2.38 3.08 3.25 3.25 3.49 4.13 4.22 V2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe2O3 / calc 28.13 28.07 27.37 27.09 27.33 26.94 26.20 25.98 MnO 0.05 0.08 0.08 0.05 0.04 0.04 0.06 0.03 MgO 0.04 0.05 0.03 0.06 0.05 0.03 0.07 0.04 CaO 33.36 33.53 33.16 33.05 33.20 33.57 33.23 33.09 Σ (calc) 100.66 100.55 100.59 100.48 100.11 99.82 100.48 100.44 Recalculated (wt. %) final Fe2O3 28.13 28.07 27.37 27.09 27.33 26.94 26.20 25.98 final MnO 0.05 0.08 0.08 0.05 0.04 0.04 0.06 0.03 Σ 100.66 100.55 100.59 100.48 100.11 99.82 100.48 100.44 Cations for 12 O atoms

Ca 2.993 3.010 2.975 2.967 2.994 3.034 2.980 2.969 Mg 0.004 0.000 0.004 0.007 0.004 0.000 0.009 0.005 Mn2+ 0.004 0.006 0.006 0.004 0.003 0.003 0.004 0.002 Na 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣX 3.000 3.016 2.984 2.978 3.000 3.037 2.993 2.977 Fe3+ 1.772 1.770 1.725 1.708 1.731 1.704 1.651 1.638 Cr 0.156 0.158 0.204 0.215 0.216 0.233 0.273 0.279 Al 0.038 0.016 0.049 0.056 0.029 0.000 0.061 0.055 Si 0.000 0.000 0.014 0.020 0.000 0.000 0.000 0.029 Ti 0.033 0.034 0.023 0.023 0.022 0.023 0.021 0.023 Mg 0.001 0.006 0.000 0.000 0.003 0.004 0.000 0.000 V 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣY 2.000 1.984 2.016 2.022 2.000 1.963 2.007 2.023 Si 2.995 2.966 3.000 3.000 2.977 2.938 2.996 3.000 Al 0.005 0.034 0.000 0.000 0.023 0.056 0.004 0.000 Fe3+ 0.000 0.000 0.000 0.000 0.000 0.006 0.000 0.000 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 1.000 1.006 0.995 0.992 1.000 1.013 0.997 0.992 EMPA Y sof Cr 1.063 1.059 1.064 1.064 1.064 1.051 1.057 1.060 EMPA Z sof 1.000 0.999 1.000 1.000 0.999 1.000 1.000 1.000 F(000) 153 153 153 153 153 153 153 152 End-Member mole %

Uvarovite 8 8 10 11 11 12 14 14 Andradite 89 89 86 85 87 85 83 82 Grossular 2 1 2 2 1 0 3 3 Schorlomite-Al 0 2 0 0 1 1 0 0 Remainder 1 1 1 1 1 0 2 1 Σ 100 100 100 100 100 100 100 100 Quality Index Good Exc Good Fair Fair Sup Fair Exc 3+ Composition: Phase-1 (pts.1-19): {Ca2.98}[Fe 1.76Cr0.17Al0.05Ti0.02Si0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12; 2+ 3+ Uv9Adr88Grs2 and Phase-2 (pts. 20-25): {Ca2.99Mg0.01Mn 0.01}Σ3.01[Fe 1.29Cr0.61Al0.06Ti0.02Si0.01Mg0.01]Σ2.00 (Si2.99Al0.01)Σ3.00O12; Uv30Adr64Grs3

132

Table A1.5. (Continuation) EMPA data of 25 analyzed points of JTC-1 from Jacksonville, California Oxide (wt. %) 17 18 19 20 21 22 23 24 25 1.2.10 1.2.19 1.2.8 1.2.18 1.2.6 2.3.10 1.2.11 1.2.9 1.2.12 SiO2 35.26 35.40 35.94 35.82 35.99 34.57 36.08 35.34 35.94 TiO2 0.57 0.30 0.39 0.37 0.44 0.40 0.42 0.27 0.28 Al2O3 0.43 0.59 0.57 0.74 0.70 0.74 0.73 0.78 0.80 Cr2O3 4.35 4.75 5.44 7.53 8.03 8.69 9.52 10.21 10.82 V2O3 0.00 0.00 0.00 0.00 0.00 0.08 0.00 0.00 0.00 Fe2O3 / calc 26.08 25.69 24.90 22.27 21.58 20.03 20.21 19.34 18.88 MnO 0.07 0.07 0.11 0.05 0.07 0.08 0.07 0.10 0.09 MgO 0.05 0.03 0.05 0.05 0.05 0.17 0.09 0.05 0.08 CaO 33.19 33.53 32.86 33.41 33.25 32.88 33.25 33.36 33.45 Σ (calc) 100.00 100.36 100.26 100.24 100.11 97.64 100.37 99.45 100.34 Recalculated (wt. %) final Fe2O3 26.08 25.69 24.90 22.27 21.58 20.03 20.21 19.34 18.88 final MnO 0.07 0.07 0.11 0.05 0.07 0.08 0.07 0.10 0.09 Σ 100.00 100.36 100.26 100.24 100.11 97.65 100.37 99.45 100.34 Cations for 12 O atoms

Ca 2.996 3.011 2.955 2.996 2.985 3.021 2.975 3.010 2.990 Mg 0.000 0.000 0.006 0.001 0.006 0.000 0.011 0.000 0.004 Mn2+ 0.005 0.005 0.008 0.004 0.005 0.005 0.005 0.007 0.006 Na 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣX 3.001 3.016 2.969 3.000 2.996 3.026 2.991 3.017 3.000 Fe3+ 1.654 1.621 1.573 1.402 1.361 1.292 1.270 1.226 1.185 Cr 0.290 0.315 0.361 0.498 0.532 0.589 0.628 0.680 0.714 Al 0.013 0.026 0.056 0.071 0.069 0.039 0.072 0.054 0.077 Si 0.000 0.000 0.016 0.000 0.015 0.000 0.012 0.000 0.000 Ti 0.036 0.019 0.025 0.023 0.028 0.026 0.026 0.017 0.018 Mg 0.006 0.004 0.000 0.005 0.000 0.022 0.000 0.006 0.006 V 0.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000 ΣY 1.999 1.984 2.031 2.000 2.004 1.974 2.009 1.983 2.000 Si 2.971 2.967 3.000 2.998 3.000 2.964 3.000 2.976 2.998 Al 0.029 0.033 0.000 0.002 0.000 0.036 0.000 0.024 0.002 Fe3+ 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 1.001 1.006 0.989 1.000 0.998 1.009 0.996 1.006 1.000 EMPA Y sof Cr 1.062 1.052 1.064 1.040 1.039 1.025 1.037 1.028 1.029 EMPA Z sof 0.999 0.999 1.000 1.000 1.000 0.999 1.000 0.999 1.000 F(000) 153 153 152 152 152 152 152 152 151 End-Member mole %

Uvarovite 14 16 18 25 27 29 31 34 36 Andradite 83 81 78 70 68 65 64 61 59 Grossular 1 1 2 3 3 2 3 2 4 Schorlomite-Al 1 1 0 0 0 1 0 1 0 Remainder 0 1 1 1 2 2 1 1 0 Σ 100 100 100 100 100 100 100 100 100 Quality Index Exc Exc Fair Sup Fair Fair Fair Good Sup 3+ Composition: Phase-1 (pts.1-19): {Ca2.98}[Fe 1.76Cr0.17Al0.05Ti0.02Si0.01]Σ2.01(Si2.99Al0.01)Σ3.00O12; 2+ 3+ Uv9Adr88Grs2 and Phase-2 (pts. 20-25): {Ca2.99Mg0.01Mn 0.01}Σ3.01[Fe 1.29Cr0.61Al0.06Ti0.02Si0.01Mg0.01]Σ2.00 (Si2.99Al0.01)Σ3.00O12; Uv30Adr64Grs3

133

Table A1.6. EMPA data of 15 analyzed points of FIN-1 from Outokumpu, Finland Oxide (wt. %) 1 2 3 4 5 6 7 2.1.7 2.1.6 2.1.2 1.1.6 2.1.1 2.1.5 1.1.4 SiO2 37.06 37.04 36.32 37.44 36.25 36.06 36.72 TiO2 0.50 0.33 0.14 0.17 0.13 0.11 0.27 Al2O3 10.33 8.26 6.03 6.60 5.98 5.71 6.24 Cr2O3 14.41 17.45 20.30 20.63 20.81 20.79 21.14 V2O3 0.07 0.15 0.24 0.00 0.27 0.23 0.00 Fe2O3 / calc 0.52 0.51 0.47 0.50 0.53 0.60 0.48 MnO 0.69 0.55 0.47 0.55 0.42 0.41 0.53 MgO 0.56 0.46 0.31 0.37 0.30 0.30 0.36 CaO 33.63 33.51 33.24 32.63 33.53 33.46 33.46 Total (calc) 97.77 98.26 97.51 98.89 98.22 97.68 99.20 Recalculated (wt. %)

final Fe2O3 0.52 0.51 0.47 0.50 0.53 0.60 0.48 final MnO 0.69 0.55 0.47 0.55 0.42 0.41 0.53 Σ(calc) 97.78 98.26 97.50 98.89 98.22 97.68 99.20 Cations for 12 O atoms

Ca 2.915 2.920 2.949 2.854 2.957 2.969 2.921 Mn2+ 0.047 0.038 0.033 0.038 0.029 0.029 0.037 Mg 0.038 0.044 0.029 0.045 0.014 0.002 0.042 ΣX 3.000 3.001 3.012 2.937 3.000 3.000 3.000 Cr 0.922 1.122 1.329 1.331 1.354 1.361 1.362 Al 0.982 0.792 0.589 0.635 0.564 0.544 0.591 Fe3+ 0.031 0.031 0.030 0.031 0.033 0.037 0.029 Ti 0.031 0.020 0.009 0.010 0.008 0.007 0.017 Mg 0.030 0.012 0.008 0.000 0.023 0.035 0.001 V 0.005 0.010 0.016 0.000 0.018 0.016 0.000 Si 0.000 0.012 0.008 0.056 0.000 0.000 0.000 ΣY 2.000 1.999 1.988 2.063 2.000 2.000 2.000 Si 2.998 3.000 3.000 3.000 2.984 2.987 2.992 Al 0.002 0.000 0.000 0.000 0.016 0.013 0.008 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 0.999 0.998 1.003 0.976 1.001 1.002 0.997 EMPA Y sof Cr 0.767 0.813 0.856 0.875 0.866 0.868 0.865 EMPA Z sof 1.000 1.000 1.000 1.000 1.000 1.000 1.000 F(000) 139 141 143 143 144 144 143 End-Member mole %

Uvarovite 46 56 66 67 68 68 68 Grossular 46 37 27 29 27 26 27 Morimotoite-Mg 3 1 1 0 0 0 0 Andradite 2 2 1 0 2 2 1 Spessartine 2 1 1 1 1 1 1 Pyrope 1 1 1 2 0 0 1 Goldmanite 0 0 1 0 1 1 0 Remainder 0 1 1 2 1 2 0 Σ 100 100 100 100 100 100 100 Quality Index Sup Fair Fair Poor Exc Exc Sup 2+ 3+ Composition: Phase-1 (pt.1): {Ca2.92Mn 0.05Mg0.04}Σ3.00[Al0.98Cr0.92Fe 0.03Ti0.03Mg0.03V0.01]Σ2.00(Si2.98Al0.02)Σ3.00O12; 2+ 3+ Uv46Grs46Mmt3Adr2, Phase-2 (pt.2): {Ca2.92Mn 0.04Mg0.04}Σ3.00[Cr1.12Al0.79Fe 0.03Ti0.02V0.01Mg0.01Si0.01]Σ2.00 (Si3.00)O12; 2+ 3+ Uv56Grs37Adr2Mmt1 and Phase-3 (pts. 3-7): {Ca2.93Mn 0.03Mg0.3}Σ2.99 [Cr1.35Al0.58Fe 0.03Ti0.01V0.01Mg0.01Si0.01] 2+ 3+ Σ2.01(Si2.99Al0.01)Σ3.00O12; Uv68Grs27Adr1; and Phase-4 (pts. 8-15) {Ca2.88Mn 0.04Mg0.4}Σ2.96[Cr1.43Al0.54Si0.04Fe 0.03Ti0.01] Σ2.04(Si3.00)O12; Uv71Grs24Sps1

134

Table A1.6. (Continuation) EMPA data of 15 analyzed points of FIN-1 from Outokumpu, Finland Oxide (wt. %) 8 9 10 11 12 13 14 15 2.1.3 1.1.8 1.1.7 1.1.1 1.1.5 1.1.2 1.1.9 1.1.3 SiO2 36.31 37.38 37.18 37.13 36.62 37.13 37.31 37.14 TiO2 0.14 0.15 0.14 0.14 0.13 0.17 0.12 0.12 Al2O3 5.43 6.13 5.76 5.86 5.68 5.49 5.45 5.31 Cr2O3 21.29 21.70 21.94 22.05 22.03 22.30 22.35 22.73 V2O3 0.22 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe2O3 / calc 0.51 0.56 0.42 0.48 0.48 0.46 0.46 0.45 MnO 0.43 0.51 0.51 0.52 0.50 0.46 0.49 0.52 MgO 0.31 0.39 0.33 0.32 0.38 0.34 0.33 0.29 CaO 33.23 32.78 32.98 33.21 33.47 32.91 32.72 33.05 Total (calc) 97.88 99.60 99.26 99.71 99.29 99.26 99.23 99.61 Recalculated (wt. %)

final Fe2O3 0.51 0.56 0.42 0.48 0.48 0.46 0.46 0.45 final MnO 0.43 0.51 0.51 0.52 0.50 0.46 0.49 0.52 Σ(calc) 97.87 99.60 99.26 99.71 99.29 99.26 99.23 99.61 Cations for 12 O atoms

Ca 2.947 2.855 2.885 2.892 2.926 2.883 2.868 2.888 Mn2+ 0.030 0.035 0.035 0.036 0.035 0.032 0.034 0.036 Mg 0.033 0.047 0.040 0.039 0.039 0.041 0.040 0.035 ΣX 3.010 2.937 2.960 2.966 3.000 2.956 2.942 2.960 Cr 1.394 1.394 1.416 1.417 1.421 1.441 1.445 1.466 Al 0.530 0.587 0.554 0.561 0.534 0.529 0.525 0.510 Fe3+ 0.032 0.034 0.026 0.029 0.029 0.028 0.028 0.027 Ti 0.009 0.009 0.009 0.009 0.008 0.010 0.007 0.007 Mg 0.006 0.000 0.000 0.000 0.007 0.000 0.000 0.000 V 0.014 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Si 0.006 0.038 0.035 0.018 0.000 0.035 0.052 0.029 ΣY 1.990 2.063 2.040 2.034 2.000 2.044 2.058 2.040 Si 3.000 3.000 3.000 3.000 2.988 3.000 3.000 3.000 Al 0.000 0.000 0.000 0.000 0.012 0.000 0.000 0.000 ΣZ 3.000 3.000 3.000 3.000 3.000 3.000 3.000 3.000 EMPA X sof 1.002 0.976 0.984 0.987 0.998 0.982 0.978 0.985 EMPA Y sof Cr 0.871 0.890 0.886 0.885 0.877 0.894 0.899 0.898 EMPA Z sof 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 F(000) 144 143 144 144 144 144 144 144 End-Member mole %

Uvarovite 70 70 71 71 71 72 72 73 Grossular 24 25 25 26 24 24 23 23 Morimotoite-Mg 1 0 0 0 0 0 0 0 Andradite 2 0 0 0 1 0 0 0 Spessartine 1 1 1 1 1 1 1 1 Pyrope 1 2 1 1 1 1 1 1 Goldmanite 1 0 0 0 0 0 0 0 Remainder 1 2 1 1 0 1 2 1 Σ 100 100 100 100 100 100 100 100 Quality Index Good Poor Fair Fair Sup Fair Fair Fair 2+ 3+ Composition: Phase-1 (pt.1): {Ca2.92Mn 0.05Mg0.04}Σ3.00[Al0.98Cr0.92Fe 0.03Ti0.03Mg0.03V0.01]Σ2.00(Si2.98Al0.02)Σ3.00O12; 2+ 3+ Uv46Grs46Mmt3Adr2, Phase-2 (pt.2): {Ca2.92Mn 0.04Mg0.04}Σ3.00[Cr1.12Al0.79Fe 0.03Ti0.02V0.01Mg0.01Si0.01]Σ2.00 (Si3.00)O12; 2+ 3+ Uv56Grs37Adr2Mmt1 and Phase-3 (pts. 3-7): {Ca2.93Mn 0.03Mg0.3}Σ2.99 [Cr1.35Al0.58Fe 0.03Ti0.01V0.01Mg0.01Si0.01] 2+ 3+ Σ2.01(Si2.99Al0.01)Σ3.00O12; Uv68Grs27Adr1; and Phase-4 (pts. 8-15) {Ca2.88Mn 0.04Mg0.4}Σ2.96[Cr1.43Al0.54Si0.04Fe 0.03Ti0.01] Σ2.04(Si3.00)O12; Uv71Grs24Sps1

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