The Chemical Activators of Cathodoluminescence in Jadeite

Erin C. Dopfel

A thesis

presented to the faculty of Mount Holyoke College in partial fulfillment of the requirements

for the degree of Bachelor of Arts with Honor

Department of Earth and Environment Mount Holyoke College

South Hadley, Massachusetts

May 2006 Thesis Advisor: Dr. M. Darby Dyar Department Chair: Dr. Mark McMenamin

ACKNOWLEDGMENTS

I would like to thank my advisor, Darby Dyar, for her patience and

guidance, and all the support she has shown toward this project over the past

year. I am also grateful to Dean Connie Allen and Mark McMenamin,

members of my thesis committee, for reading this document and providing me

with extraordinarily helpful suggestions. And to the faculty of Mount

Holyoke’s Department of Earth and Environment, especially Michelle

Markley, Al Werner, and Steve Dunn, who have acted not only as mentors,

but as true friends.

Endless thanks to the donors of the Mount Holyoke Summer Research

Fellowship, the Martha Godchaux Field Scholarship, and the Department of

Earth and Environment funds, as well as Darby Dyar and the Sorena Sorensen,

for supporting my travels and research expenses.

Thanks to Mike Jercinovic at the University of Massachusetts –

Amherst Microprobe Lab, who somehow managed to run all of my EPMA

analyses on the shortest-notice-known-to-man. I am especially grateful to

William F. McDonough and Richard Ash at the University of Maryland’s

Isotope Geochemistry Lab, for allowing me to utilize their facilities to collect

my LA ICP-MS data. Also, thanks to Gerard Marchand, Yarrow Rothstein,

and Eli Sklute of Mount Holyoke College for helping to prepare and change

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samples, and fit messy Mössbauer curves. And for all their reference

assistance and statistical know-how, I must thank Mount Holyoke’s library

staff, especially Sarah Oelker, Mary Glackin, and Jim Burke.

Special thanks must be given to Dr. Sorena S. Sorensen, of the

National Museum of Natural History, for sharing with me her lab, samples,

guidance, and friendship.

And lastly, thank you to my friends and family, for their endless

encouragement, patience, and love.

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ABSTRACT Jadeite, nominally NaAlSi2O6, has long been observed to emit green,

blue, or red luminescence. The chemical origin of these phenomena is

currently unclear. The goal of this study is to determine the chemical

activators of cathodoluminescence (CL) in Na-rich pyroxene using chemical

characterization by four analytical techniques. Seventeen samples of jadeite

from Guatemala, Burma, California, Russia, and Japan were selected from the

collections of the Smithsonian National Museum of Natural History (NMNH).

These samples were analyzed using the electron microprobe for major

elements, Mössbauer spectroscopy for Fe3+/Fe2+, ICP-MS for trace and minor

elements, and CL for emission energies. The complete chemical data acquired

from these techniques are used to examine the variations in jadeite chemistry

as a function of paragenesis, and to link the chemistry of these minerals with

their luminescent behavior.

Samples were qualitatively assigned to either dull green CL, bright

green CL, blue CL or red CL. Prominent peaks were identified at 442 nm,

561-579 nm, and 682 nm. The source of jadeite’s “blue band” at 442 nm has

previously been hypothesized to be due to the presence of one or more

unknown defect centers (Ponahlo, 1999). However, the CL analyses of

tectosilicates have concluded that peaks in the 400 nm-range are correlated

with the abundance of Al3+ or Eu2+. Results of this study show that the

influence of Al3+ on the intensity of this peak is especially significant. The

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“green peaks” observed between 561 – 579 nm have been assigned by

previous studies of feldspars and pyroxenes to represent contributions from

Mn2+ ions. This Mn2+ peak is also observed in pyroxenes and many other

silicate minerals, including feldspars. Despite a general consensus that Mn2+ is

the primary activator in green luminescence, this study suggests that this wide

peak is, in fact, a series of smaller peaks stacked side-to-side. Results from

ICP-MS analyses show that a handful of REE’s, including Dy and Tm, are

also correlated with the intensities in the energy range of 570-590 nm. The

intensity of the red peak at 682 nm is well-correlated with the presence of Al3+,

Ti2+, Ca2+, and Eu3+, as suggested by previous work. Mössbauer data acquired

as part of this study allow us to constrain separately the influence of Fe2+ and

Fe3+ on both the intensities of luminescence and the activation of red emission

energies. While this research brings light to the possible luminescence

activators in jadeite, it is evident that the uncertainties in these studies require

further research in order to bring more quantitative insights to the origin of

such luminescence phenomena.

v

TABLE OF CONTENTS ACKNOWLEDGMENTS ................................................................................ ii

ABSTRACT..................................................................................................... iv

TABLE OF CONTENTS................................................................................. vi

LIST OF FIGURES ........................................................................................ vii

LIST OF TABLES......................................................................................... viii

INTRODUCTION ............................................................................................ 1

BACKGROUND .............................................................................................. 3

GEOLOGY OF JADEITE .............................................................................. 18

MINERALOGY OF JADEITE....................................................................... 20

METHODS ..................................................................................................... 22

RESULTS ....................................................................................................... 29

Cathodoluminescence Petrography ............................................................. 29

Peak Identification: Summer 2005........................................................... 29

SEM CL – Summer 2005 ......................................................................... 32

Grain Mount CL: Spring 2006 ................................................................. 34

Electron Microprobe Analysis..................................................................... 36

LA ICP-MS Analysis................................................................................... 40

Mössbauer Spectroscopy ............................................................................. 42

DISCUSSION................................................................................................. 44

Intensity Discrepancies................................................................................ 44

Contributions to Activation and Quenching of Jadeite CL ......................... 46

Blue Peak.................................................................................................. 49

Green Peak ............................................................................................... 50

Red Peak................................................................................................... 53

Future Work................................................................................................. 56

CONCLUSION............................................................................................... 57

REFERENCES ............................................................................................... 58

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LIST OF FIGURES Figure 1 Qualitative picture of the interaction of an electron beam with a solid.. .................... 5 Figure 2 Cross-section of luminoscope. (From Herzog et al. [1970])........................................6 Figure 3 The basic process of luminescence...............................................................................7

Figure 4 The relationship between color of emitted light (a) and the wavelength.....................8

Figure 5 Quantum model of a sodium atom.............................................................................. 9 Figure 6 Energy diagram for free molecule made up of two atoms of the same species..........11

Figure 7 Crystal structure of jadeite........................................................................................ 21 Figure 8 Calculation of relative peak intensities. .................................................................... 26 Figure 9 Example of oscillatory zoning in Guatemalan jadeitite sample 108369.. ................. 29 Figure 10 Multiple crystallization sequences illuminated by CL............................................ 30 Figure 11 Examples of different luminescence in jadeite (green CL)..................................... 31 Figure 11 (cont.) Examples of different luminescence in jadeite (red and blue CL) .............. 31 Figure 12 SEM CL and macroscopic CL, with corresponding and spectra. ........................... 33 Figure 13 SEM CL spectrum vs. CL spectrum along same scale.............................................34

Figure 14 Example of laser ablation damage on grain mount..................................................35

Figure 15 Average MnO weight % by CL type. ..................................................................... 39 Figure 16 Average Cr2O3 weight % by CL type.. .................................................................. 39 Figure 17 Average FeO weight % by CL type.. ...................................................................... 39 Figure 18 Relative intensity vs. peak position. ....................................................................... 45 Figure 19 Weight % Al2O3 vs. Intensity of blue peak (430 – 450 nm).....................................50 Figure 20 Abundance of Ti4+ (ppm) vs. Intensity of blue peak (430 – 450 nm). .................... 50 Figure 21 Weight % of MnO vs. Intensity of green peak (570 – 590 nm)............................ ...51 Figure 22 Weight % of CaO vs. Intensity of green peak (570 – 590 nm)................................51 Figure 23 Abundance of Dy (ppm) vs. Intensity of green peak (570 – 590 nm)..................... 52 Figure 24 Abundance of Tm (ppm) vs. Intensity of green peak (570 – 590 nm). ................... 52 Figure 25 Weight % of Al2O3 vs. Intensity of red peak (670 – 690 nm)..................................54

Figure 26 Abundance of Ti (ppm) vs. Intensity of red peak (670 – 690 nm).......................... 54 Figure 27 Weight % of CaO vs. Intensity of red peak (670 – 690 nm)....................................55 Figure 28 Overall abundance of REE (ppm) vs. Intensity of red peak (670 – 690 nm). ......... 55

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LIST OF TABLES

Table 1 Energy level differences for excited states of Na atoms and ions.................................9

Table 2 Assigned and conjectural activators of luminescence peaks.. .................................... 16

Table 3 Sample list of chemically analyzed jadeitites............................................................. 23

Table 4 Elements, standards and count times used for EPMA analysis.................................. 27

Table 5A Peak energies from thin section CL (‘Summer 2005’)............................................ 32

Table 5B Peak energies from grain mounted jadeite (‘Spring 2006’)..................................... 36

Table 6 Recalculated EPMA data for jadeite samples. ........................................................... 37

Table 7 ICP-MS results, separated by CL type (dull green CL).. ........................................... 40

Table 7 (continued) ICP-MS results, by CL type (bright green and red CL).. ........................ 41

Table 7 (continued) ICP-MS results, by CL type (blue CL).. ................................................. 42

Table 8 Results from Mössbauer Spectroscopy. ..................................................................... 43

Table 9 Samples separated by date of CL analysis. ................................................................ 46

Table 10 Proposed activators of luminescence and raw jadeite correlations. ......................... 47

Table 11 Proposed activators of luminescence and correlations by date..................................47

Table 12 Proposed activators and final jadeite correlations.. .................................................. 49

viii

INTRODUCTION This project integrates four analytical techniques in order to determine

the chemical activators that determine luminescence in the mineral jadeite.

Geochemical and luminescence data were collected through the integration of

CL spectroscopy, electron microprobe analysis for major and minor elements,

LA ICP-MS analysis for minor and trace elements, and Mössbauer

spectroscopy for the ratios of Fe2+/Fe3+.

The jadeites used in this study come exclusively from jadeitite

(NaAlSi2O6), a near-end-member jadeite pyroxene rock that occurs in strongly

metamorphosed, sodium-rich serpentinites. Jadeitite is usually grayish-green

in color, but can also demonstrate white, blue-gray, or mauve color

characteristics. Green jadeitite is the most popularly recognized rock form of

jade, and is highly valued in some non-Western cultures. The material’s color,

toughness, and vitreous luster have made it a timeless medium for ornamental

carvings, tools, and gems.

Geologically, jade is evidence of water’s movement within the Earth’s

crust and lithosphere. Such movement causes changes in bulk-rock chemistry

and mineralogy, which in turn create ore deposits or contribute to subduction-

related volcanic and seismic hazards. Thus, a quantification of

cathodoluminescence phenomenon will elucidate the chemical effects of

subducted water on rock formation and movement.

1

Jadeite exhibits cathodoluminescence in blue, green and red

wavelengths of visible light, and usually shows strong zoning – a feature that

evidences sequences of crystallization during rock formation. However, no

study has investigated the actual chemical components that determine the

luminescence of this material. Such information is imperative to quantitative

analysis of cathodoluminescence. Previous research has hypothesized that the

most significant activators of CL in feldspars and some pyroxenes are Al+3

and trace elements including Mn+2, Ti+3, Fe+2, Fe+3, Cr+3, Pb+2, Eu+3 and REE

elements. This paper tests such hypotheses in order to gain a better

understanding of the luminescence activators of jadeite.

2

BACKGROUND

Cathodoluminescence petrography and spectroscopy have become

routine techniques for recognizing mineral provenance, growth, diagenetic

textures, and mineral zonation. However, CL is the least understood of all

luminescence phenomena. In the past, CL has been used to generate brightly

colored images that were usually qualitatively interpreted. Today, CL

microscopy is becoming a more quantitative technique, integrating the use of

spectrometers and microprobes in order to understand the physics and

chemistry behind CL. These quantitative investigations are vital and,

according to many scientists in the field of CL, necessary because “much

more could be done with CL” (Pagel, 2000).

Luminescence is the release of nonthermal radiation from a material

when that material interacts with an energy source. The general term includes

both phosphorescence and fluorescence phenomena, which are delineated

only by the length of time at which radiation ceases after the exciting energy

has been removed. More specifically, fluorescence is the radiation that ceases

within 10-8 s after the excitation has been removed. Phosphorescence is

radiation that continues after this point (Leverenz, 1968).

Different types of luminescence are defined by the nature of the

exciting energy. For instance, chemiluminescence refers to luminescence of

materials as a result of a chemical reaction, whereas bioluminescence is

chemiluminescence in living organisms, such as seen in the glow of fire flies.

3

Photoluminescence is the term used when luminescence is caused by the

excitation of photon impacts, such as the luminescence seen in minerals under

‘black light.’ Roentgenoluminscence refers to the excitation of luminescence

by X-ray bombardment. Ionluminescence occurs when materials are

bombarded by an energetic ion beam. Finally, CL is the release of photons

from a solid that is excited by energetic electrons.

The main advantage of CL is the range of energies available to the

user. Electron energy can be as high as 50keV in some instruments, such as

the electron probe, compared to the typical 1.8 – 4.9keV photon energy from a

UV ‘black light.’ Under the weak energy of UV light, only a limited number

of minerals will exhibit photoluminescence, whereas most minerals that are

non-conductive and not opaque will show some luminescent phenomena

under the higher energies available through CL (Marshall, 1988).

When an electron beam comes into contact with a solid, a number of

different physical processes take place, including the production and emission

of X-rays, secondary and back scattered electrons, and CL (Figure 1A). A

portion of the energy is also expended through heating of the sample. The

energy from the incident beam is at a maximum when it enters the sample,

and decreases with distance into the solid as energy is lost through various

mechanisms. X-rays are most efficiently generated at the highest beam energy,

while the energies used to generate CL are on the low end of the energy scale,

near the limits of the beam penetration. The penetration depth increases with

4

an increase in beam energy, and beam voltages from 10 – 20 kV are believed

to reach depths estimated to be 2 – 8 µm (Figure 1B) (Beaman and Isasi,

1972).

A

B Figure 1. Qualitative picture of the interaction of an electron beam with a solid. A)

Different types of emitted energy after interaction. B) Where d = beam diameter, L = a distance estimated to be in the 2 – 8 um range for nonmetallic minerals. D1 is the enlarged diameter at the edge of which secondary X-rays are observed. D2, the diameter over which CL is produced. D2 – D1 = the area in which CL energy is generated. (Modified after Götze [2000] at www.geo.uw.edu.pl/ERASMUS/files/ApplMin.pdf, and Beaman & Isasi [1972] at www.geol.lsu.edu)

5

In cold cathode CL, a broad beam of accelerated electrons (produced

by an electron gun, such as a cathode ray tube) is aimed at the surface of a

polished mineral mount or rock thin section that is under a high vacuum. The

electron beam is formed in a cold cathode discharge, is bent through a

focusing coil, and then comes under the influence of a deflection magnet. The

bent and shaped beam then hits the sample. The emitted energy is directed

into an optical microscope, on which a spectrometer is sometimes mounted

(Figure 2). The energy is then collected as images and emission spectra, which

allow the user to precisely identify individual components of luminescence.

The color expressed in these images is determined predominantly by elements

that are present in a mineral at equivalent valence states within specific sites

in a crystal lattice (Pagel et al., 2000). Because the CL is observed from the

same surface that is being bombarded, either thin or thick samples can be

examined.

Figure 2. Cross-section of luminoscope. (From Herzog et al. [1970])

Upon interaction with an electron beam, the electrons in the sample

will become excited, promoting electrons from the valence band (E1) into the

conduction band (E2). Each excited electron remains in the conduction band

6

briefly, and upon relaxation, photons are released. The relaxed electron can

return directly to the ground state (Figure 3), where an emitted photon

corresponds to the energy differences E2 – E1. If, during relaxation, an

electron returns through an intermediate state (E4), then one emitted photon

corresponds to the energy differences E3 – E4, and another corresponds to E4

– E1.

Figure 3. The basic process of luminescence. In (a) an electron associated with a neutral or ionic species is excited to a higher energy level (in nm), E2, and subsequently returns from the excited state to the ground state, E1. A photon wavelength corresponding to the energy difference E2 – E1 is emitted. In (b) an electron is excited to the level E3 from where it returns via an intermediate energy level, E4, and then to the ground state E1. The photon released corresponds to the energy E3 – E4 and another photon corresponds to E4 – E1. (From Marshall 1988)

Such explicit energy emissions correspond to different wavelengths

predominantly in the visible (but also in UV and IR) wavelengths. The visible

range of energies is found between 400 – 700 nm, corresponding to energies

between 1.77 – 3.10 electron volts, where 1 eV = 1,239.8 nm (Figure 4). In

order to understand CL, it is important to understand the energy levels of

electrons in a mineral.

7

Figure 4. The relationship between color of emitted light (a), the corresponding wavelength (Å) (b), and energy (eV) (c) of the emitted photons, for spectrally pure

light. (From Marshall 1988, modified after Nassau 1978).

An isolated atom in free space contains electrons that occupy different

energy levels surrounding the nucleus of that atom. For example, a neutral

sodium (Na) atom at ground state can be written in standard quantum

mechanical notation as 1s22s22p63s, meaning there are two electrons in the

first shell s-orbitals, two electrons in the second shell s-orbitals, six electrons

in p-orbitals in the second shell, and a single electron in the third shell (Figure

5).

8

Figure 5. Quantum model of a sodium atom. The 3s orbital is half-filled in the neutral sodium atom. (©How Stuff Works, 2001 at http://js082.k12.sd.us)

A neutral atom is raised to a higher energy state through interaction

with an energetic source, in this case an electron beam. Electrons are then

promoted to higher energy levels, as derived through complicated quantum

mechanical theory and experiment. Such experiments have determined that

the neutral Na atom’s excited electron is most likely to be the 3s electron. For

further illustration, the energy levels of excited states of sodium are shown in

Table 1. This table shows that the excited state of lowest energy for Na is

found at a doublet in the 3p orbital; a return to the ground state (3s) from the

3p levels results in the emission of yellow light at 589.6 and 589.0 nm.

Energy Levels

Wavelength of photon (nm)

Energy ∆ from ground state

Sodium atom: 1s22s22p63s3s ground state 03p (doublet) 589.6 2.102 . 589.0 2.104 4s 388.0 3.19 3d 343.0 3.62 …. ionization 241.3 5.14 Sodium ion: 1s22s22p6

2p6 ground state 3s (doublet) 37.7 32.84

Table 1. Energy level differences for the first few excited states of Na atoms and ions (values converted from Moore’s [1949, 1952] tables of wavenumbers). After Marshall [1988].

9

The excited levels for a neutral sodium atom extend to the limiting

energy of 5.140eV: the energy at which the electron is completely removed

from the Na atom, also called the first ionization potential of the atom. When

this electron is removed, a sodium ion (Na+) is born. The energy levels for

such an ion are discussed in the same way as those of the neutral atom, except

that the ground state is now that of the singly charged ion that has two

electrons in s-orbitals and a full second shell, in which six electrons exist in

the p-orbitals (also referenced in Table 1). Because the ion’s second shell is

now full, the ion requires significantly more energy to excite and remove an

electron from it. The first available energy level to which one of the electrons

in Na+ can be excited is 32.8eV above the ground state of the ion. Thus,

emissions resulting from this excitation are outside of the visible range (in the

UV).

While the physics of luminescence in individual ions is important, the

conceptualization of a molecule’s energy levels is most applicable to

understanding luminescence phenomena in mineralogy. To introduce these

concepts, it is useful to begin with a diatomic molecule made of two identical

atoms. Imagine two balls (atoms) on a spring. The spacing between these two

balls oscillates about an average separation, the amplitude increasing with

increasing temperatures. The ground state of this molecule can be illustrated

by drawing the envelopes, or tangential curves, of the two extremes of the

oscillation for different temperatures (Marshall, 1988) (Figure 6). This ground

10

state is given the name E1. When this diatomic molecule is excited by some

energy, the state of electron excitation can change to a higher level. This

higher, excited level also has multiple energy levels, and can also be

represented by a curve that represents both envelopes (E2), of the same form

as curve E1. The difference in ground and excited states can be calculated

along these curves. Figure 6 illustrates that the total energy of the system is

constant, but the relative amounts of potential and kinetic energy change as a

function of nuclear separation. This diatomic system spends the majority of

time in the state where its potential is a minimum. Thus, electron promotion

after energetic excitation is most likely to take place from one energy level to

another.

Figure 6. Energy diagram for a hypothetical free molecule made up of two atoms of the same species. To explain: the ground state can have several different levels of vibrational energy and the envelopes of the amplitude of oscillation of each of these defines the potential energy curve for the ground state, E1. Thermal agitations, or small amounts of external energy input, can cause transfer between vibrational energy levels in the ground state, eg. a1 – c1 to a2 – c2. Absorption of larger amounts of external excitation energy, eg. Ea from an energetic electron or photon, can excite the system to the vibrational levels a2* – c2* on energy state E2*. From this level, by small energy losses it can change to a1* – c1*. Finally, the excited system can return to the ground state at a4 – c4, emitting a photon of energy Ee. (modified after Leverenz [1968], from Marshall, 1988)

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This model of diatomic molecules is useful in the study of gas

molecules, but less practical when studying mineral solids. In solids, the

situation is more complex, because each atom or ion is surrounded by several

neighbors, whose number and identity vary within each mineral lattice. The

concept of a ‘configurational coordinate’ is used to describe this situation.

Fortunately, the same diagram of energy levels used to discuss a diatomic

molecule is used to discuss the energy levels of an atom or ion in a solid (see

Figure 6). The configurational coordinate is the average of interatomic

spacings for a large number of ions, as each ion or atom within this lattice is

oscillating in its position with respect to all of its neighbors’ oscillations. For

instance, if Na is incorporated into a mineral such as halite (NaCl), then the

energy levels are those of the ion Na+. The energy levels of Na+ begin in the

UV wavelengths, so electrons in Na+ do not produce visible CL. NaCl is a

crystal lattice with composite energy levels, so the influence of the remaining

Cl- and Na+ ions in the crystal on the energy levels of the Na+ ion must be

considered. For the case of Na+ in halite, the effect of the crystal on visible CL

is negligible, because pure halite shows little or no CL (Teergarden, 1966).

Similarly, the CL of calcite cannot be associated only with the states of Ca2+

ions in the crystal, but must be a product of the energy levels within the

crystal lattice (Habermann et al., 2000). This inevitably raises the theoretical

question, “Do pure minerals emit visible CL?” It would seem that there are

many crystals to investigate, and that of all the possible cases, there would be

12

at least some available energy levels in an ideal crystal that would produce

visible light emissions. However, most of the purest crystals do not

demonstrate any visible CL. For example, very pure apatite, formed under

oxidizing conditions that disallow the introduction of Mn2+ (a known activator

of CL) and other impurities, is non-luminescent. This is a good example of the

crystal’s inherent limitations on emitted CL. The emitted energy of a mineral

is primarily determined by defects and impurities in a crystal lattice. To

simplify the matter, scientists have sorted luminescence into two categories:

intrinsic or impurity-activated CL.

Intrinsic luminescence is the emission of visible CL in pure crystals,

such as is seen in phosphors, and natural and synthetic minerals (Marshall,

1988). It can be activtated by nonstoichiometric chemistry (a pure mineral that

does not have exactly the correct elemental proportions), and structural

imperfections. For instance, there is evidence that intrinsic luminescence in

many minerals is associated with defects, and that crystals that form at higher

temperatures (meaning more defects) are more brightly luminescent than

crystals of the same mineral that are formed at lower temperatures. For

example, authigenic feldspars show almost no CL, whereas feldspars formed

at higher temperatures almost always show CL (Götze, 2000).

Activators of CL tend to be impurities, or trace elements, in the crystal

lattice. Generally these activators are believed to be substitutional. In

geological materials, more than one of these activator impurities is often

13

present in a mineral at one time. The role of impurities as activators relates

directly back to energy levels for ions in a solid. Because the example of Na is

not an activator of visible CL, we will discuss manganese (Mn), an element

that is an important activator in many of the common minerals.

The common ionic form, Mn2+, regularly substitutes for Ca2+ and Mg2+.

The configuration of a neutral Mn2+ ion is (Ar core)3d54s2. This atom has five

electrons in a half-filled D shell, meaning that the electrons are easier to excite

than those in a filled shell. When Mn2+ is incorporated into a crystal structure,

the composite energy levels are still obtained from complicated quantum

mechanical equations. However, the physics becomes more complicated at

this point, because the energy levels of the impurity must be affected by the

crystal field and other ions surrounding the activator (Mn2+).

Crystal field theory is an approach used to determine the relative

effects of surrounding ions and activators on the magnitude of energy levels

and energy splitting (Burns 1993). In crystal field theory, the metal ion is

assumed to be free in gas form, and the ligands (defined as an ion, molecule,

or molecular group that binds to another chemical entity to form a larger

complex) are assumed to behave like point charges. The assumption is also

made that the orbitals of the metal ion and the ligands do not interact. Because

the precise crystal structures and fields of minerals cannot be known, the

complex calculations cannot be completed. Thus, the approach in this theory

is to make an approximate calculation of the energy levels as a function of Dq,

14

a parameter defined by the strength of the crystal field, especially the spacing,

charge, and nature of the anions surrounding the activator ion (Orgel 1966).

The energy levels and differences of energy levels vary with Dq and

sometimes the relative positions of the energy levels will actually change

(Marshall, 1988). This brief description of crystal field theory serves to

demonstrate the complication behind determining the energy levels of certain

activators in different crystal lattices. The collective significance of crystal

field theory in CL indicates that the stronger the interaction of the activator

ion with the lattice, the greater the width of the emission line.

The determination of specific activators has been investigated in

experiment, theory, and the literature since as early as 1955. Most of this work

has focused on the CL of sedimentary rocks and gems, with more recent

research being conducted on both igneous rocks and meteorites. The

utilization of CL in metamorphic studies is still fairly recent. Results

conclusively assign at least nine trace-element activators to specific

luminescence peaks (Table 2).

15

Wavelength (nm) Element/ Defect Center

Citation

294 Pb+/Pb2+ Marfunin (1979), Tarashchan et al. (1973) 355 Ce3+ Mariano and Ring (1975) 410 – 418 Unknown in jadeite Ponahlo (2000) 420 Eu2+/3+ Mariano and Ring (1975) 450 Al3+ Marfunin (1979) 470 AlO4

-4 center Tarashchan et al. (1973) 480 Fe2+/Ti4+ Rossman (2001) 490 Ni2+ Götze (2000) 490 Ce3+ Jaek et al, (1996) 500 Si+ Marfunin and Bershov (1979) 550 - 640 Mn2+ Machel (2000) 570 Dy3+ Götze et al. (1996) 590, 640 Sm3+ Götze et al. (1996) 686 - 700 Cr3+ Marfunin (1995) 686 - 700 Fe3+ Mariano et al. (1973), Mora and Ramseyer (1992) 760 Unknown Ponahlo (2000) Unknown influence Ca:Fe Götze (2000) Unknown influence Ca2+ Götze (2000) Unknown influence REE2+/3+ Götze et al. (1996), Pagel (2000) Unknown influence Gd3+ Götze et al. (1996) Unknown influence Tm3+ Gorobets and Rogojine (2002) Effects Intensity Fe2+/Mn2+ Machel (2000) Quencher Fe2+ Machel (2000)

Table 2. Assigned and conjectural activators of luminescence peaks. Adapated from Götze (2000)

The most quantitative investigations of CL have analyzed synthetic and

‘doped’ minerals, in which overall crystal chemistry is better understood than

in natural minerals (Blanc et al., 2000). Such investigations have allowed the

assignment of emission peaks to specific elemental inclusions. This paper

works on the assumptions that the activators of previous research, which has

been conducted on other minerals, are applicable to the crystal chemistry of

the mineral jadeite.

Many elements serve as activators in CL, especially transition metals

and REE. In addition to Mn2+ and Eu3+, other frequently encountered elements

16

in CL include Cr3+, Fe3+, Pb2+, and Ti4+(Götze, 2000). The elements that are

permitted to enter the crystal lattice are governed by factors such as ionic

charge, size, and coordination number. The included activator’s effect on

emitted CL energies depends heavily upon the complicated solid-state physics

and crystal field theory as described above. When a mineral contains more

than one activator, as is commonly the case, the locations of the CL emissions

spectrum peaks are changed slightly (Marshall, 1988).

Along with activators, there are sensitizers of luminescence, which

augment the luminescence of a material, and quenchers of luminescence,

which detract from the luminescent properties of a material. For instance,

previous research has shown that Pb2+ and Ce3+ are important sensitizers of

Mn2+-activated luminescence in carbonates (Machel, 2000). The strongest

quencher of Mn2+ luminescence in carbonates and many other minerals is Fe2+,

but research has shown that Co2+, Ni2+, and Fe3+ might also have quenching

affects in certain crystals (Machel et al., 1991).

This previous research indicates that more research needs to be

conducted, especially on green luminescence phenomena (500 – 590 nm). The

broadness of wavelength assignments for most main green CL activators, such

as Mn2+, Cr3+, and Fe3+, and the previous correlation of REE to similar ‘green

peaks’ suggests that the peaks observed in jadeite may well be composites of

more than one peak.

17

GEOLOGY OF JADEITE

The term ‘jade’ commonly refers to two different types of

metamorphic rocks, jadeitite and nephrite. Both types form from serpentinite

bodies, within convergent-margin tectonic settings. Nephrite is the amphibole-

rich jade. It forms by the replacement of serpentinite by Ca- and Si-rich

aqueous fluids under low-pressure and low-to-moderate temperature

conditions, such as those that occur following obduction. Jadeitite, or jadeite

rock, is the pyroxene-rich member of the jade family. This rock forms under

high-pressure and low-temperature conditions during subduction or collision

events, when Na-Al-Si–rich aqueous fluids interact with peridotite that is

being serpentinized (Harlow and Sorensen, 2005). Both rock types are

extremely tough and, depending on their grain size, sometimes stronger than

steel.

Nephrite is the most abundant form of jade, and demonstrates only a

few color varieties from creamy white to green. Jadeitite is less common, and

is found in only eight localities worldwide, mainly the (1) Tawmaw Region of

the Jade Mines District, Burma (Myanmar); (2) central Motagua Valley,

Guatemala; (3) Omi-gawa and Kotaki-gawa drainages, Japan; (4) Oeyama

ophiolite, Japan (5) Ketchpel River , Polar Urals, Russia; (6) Itmurundy area,

Kazakhstan; (7) Yenisey River region, Khakassia (West Sayan, Russia); and

(8) New Idria, California (Sorensen and Harlow, in review). Jadeitite usually

occurs as a grayish-green rock, but can be found as white, blue-gray, or mauve

18

varieties. Green jadeitite is the most popularly recognized form of jade,

although it is the least common. The material’s color, toughness, and vitreous

luster have made it a timeless medium for ornamental carvings, tools, and

gems.

Geologically, jade rock is evidence of water’s movement within the

Earth’s crust and lithosphere. Such movement causes changes in bulk-rock

chemistry and mineralogy, which in turn create ore deposits or contribute to

subduction-related volcanic and seismic hazards. Because jadeite is

commonly associated with albitite, an albite-rich rock that texturally

resembles granite, early researchers hypothesized that jadeitite was formed by

the metasomatism of granite or other felsic protoliths (Chhibber, 1934;

Chihara, 1971; Dobretsov, 1964). More recent studies prove, however, that

jade’s protolith is serpentinite (Harlow and Sorensen, 2005). Evidence of this

can be seen in the position of massive jadeitite bodies, which are usually

isolated within serpentinite-matrix mélanges. Commonly related rock types

include sodic-amphibole rocks, eclogite, garnet amphibolite, and blueschist.

19

MINERALOGY OF JADEITE

Jadeite is found only in metamorphic rocks, where it replaces

nepheline or albite, minerals between which jadeite’s composition lies. Jadeite

can be distinguished from these two minerals primarily because it forms at

much higher pressures. It is commonly zoned, indicating multiple

crystallization sequences and more than one fluid source (Harlow and

Sorensen, 2005).

Jadeitite consists almost entirely of the sodium-rich C2/c pyroxene

jadeite, nominally Na(Al,Fe3+)Si2O6. Common impurities in this mineral

include Ti, Mn, Mg, Ca, K, and H2O. Structurally, jadeite is a monoclinic

clinopyroxene, composed of single chains of silica tetrahedral that share two

of their four corners (Figure 7). Al is regularly found in the M1 sites, while Na

is usually found in the M2 sites. Deer et al. (1997) indicate that, in fact, more

than 80% of the M1 and M2 sites are occupied by Al and Na, respectively,

leaving room for very little substitution. There is occasional replacement of Si

by Al and Fe3+ in the tetrahedral coordination. Al in the M1 site is commonly

replaced by Fe3+, Fe2+, Cr, Mg, Mn, especially in zoned jadeite (Deer et al,

1997). Na in the M2 site is commonly replaced by Ca, Li, and the REE. These

crystal chemical substitutions are generalized assumptions made from overall

pyroxene analyses. The only single crystal structure refinement that has been

conducted on jadeite has concluded that Cr3+ does, in fact, rest in the M1 site

20

(Khomenko and Platonov, 1985). Regardless, the chemical constraints suggest

that CL could be activated by a large number of possible cation substitutions.

Figure 7. Crystal structure of jadeite (Wyckoff, 1994 at www.staff.aist.go.jp)

21

METHODS Sample Selection

Samples for this study were chosen by Sorena Sorensen from the

collections at the National Museum of Natural History (Table 3). The criteria

by which samples were chosen were overall luminescence type in thin

section/hand sample, abundance of sample, and locality. Hand samples range

in color (in visible light) from dark green-grey to creamy green, to pale

lavender and pink. Under CL, samples demonstrate red, blue, magenta, and

green luminescence. In order to limit the geographic and geologic variability,

all green-luminescent samples were chosen from Guatemalan jadeitite hand

samples. None of these jades consisted of translucent gem-quality material, or

“imperial” jade, because Cr3+ rich jadeite is non-luminescent.

Thin Sections and Grain Mounts

Thin sections of green-luminescent jades were made by the NMNH.

These sections were extensively examined and photographed for CL under

both a luminoscope and a Scanning Electron Microscope (SEM). In order to

facilitate sampling and analysis, grain mounts of all green, red, and blue jades

were made by G. Marchand at Mount Holyoke College. To avoid the

inclusion of weathered or macroscopically imperfect jadeite, every grain was

chosen by hand. Samples were mounted and polished to a thickness of 35μm.

They were later analyzed using the electron microprobe, LA ICP-MS, and CL.

22

Sample Name Country Rock Color Overall CLMVE04-14-2 Guatemala dark grey-green dull green 01GSn 2-11 Guatemala forest/emerald green dull green MVE02SS-26-06 Guatemala creamy green dull green 108369 Guatemala brilliant apple green dull green 01GSn 1-5 Guatemala white and light green bright green MVJ-90-24-1 Guatemala white and light green bright green MVE02SS-39A Guatemala creamy green bright green SS04-16B Guatemala creamy green bright green 112538 Guatemala creamy green bright green BUR-07 Burma pale pink red 94303 Burma pale lavender red J-33-C California light green red KB10J-SS Burma straw green red NBJ-01 Burma gray-lavender blue KB10J-10 Burma straw green blue R3076 Burma pale lavender blue RGC4B Japan white blue

Table 3. Sample list of chemically analyzed jadeitites, organized by qualitative CL type. All samples borrowed from the National Museum of Natural History.

Mössbauer mounts were created by first grinding 120mg of jadeite

using a diamonite™ mortar and pestle. Ground samples were then ground

with sugar in the presence of acetone, an alcohol that prevents oxidation. The

sugar and grinding assure random orientation in the sample. The jadeite

powder was then loaded into 34 mm diameter sample mounts. One side was

sealed with an adhesive plastic cap, and the other with thermal tape.

Cathodoluminescence Spectroscopy

A Premier American Technologies luminoscope model ELM-3R,

located in the Department of Mineral Sciences at the National Museum of

23

Natural History, Washington DC, was used to study the CL properties of

jadeite rock. The electron beam was run under a vacuum of <100 torr between

15-20 kV and 0.5 mA. Attached to the luminoscope is a microscope, on which

is mounted an Olympus Opelco MagnaFire Model S99806 camera. The

camera works by capturing three digital grayscale images with a 1300 x 1030

pixel monochrome CCD through a rotating Red-Blue-Green (R-B-G) color

filter wheel. The complementing MagnaFire software then produces a final

image by combining the three R-B-G images.

Samples were observed through the luminoscope’s glass window and

qualitatively assigned to either bright green, dull green, red, or blue

luminescence. Digital images were then collected at magnifications of 10X. In

order to reproduce the colors observed through the glass window of the

vacuum chamber, the CL images were processed in Adobe Photoshop CS-8.0.

All images were adjusted using the “auto-levels” contrast and “brightness”

tools, as these optimized the image’s appearance without compromising the

original color as it appears to the operator’s eye through the glass window.

Additionally, in order to assign a numeric value to the luminescence

properties, a spectrum of the visible light emitting from each sample was

collected. A corundum standard was used to calibrate the instrument each day.

The exposure of each analysis was 25 seconds, through a slit width of 1.3mm.

The total area of light that is collected by the spectrometer is about 67%, or

1.71mm2, of the total area of the image (Sorensen, personal communication).

24

Scanning Electron Microscope CL

SEM CL data were acquired using a JEOL 840A Scanning electron

microscope, on which a Gatan MonoCL3 was mounted. Thin sections were

carbon coated and run under a vacuum, with an accelerating voltage of 7kV

and a beam current of 10nA. Because of the nature of the spectrometer,

spectra could only be collected at high magnifications (>140X), and the beam

(<1 mm) was focused on individual, sub-micron zones in jadeite, at

magnifications of 7500X. These analyses were run only on thin sections

during summer 2005.

Peak Position and Intensity Calculation

The relative peak intensities on all conventional CL spectra were

determined through the means of drawing a background line through the

spectrum graph and measuring peak height from said background line (0)

(Figure 8). The heights were then translated into a ‘count number’ relative to

the scale on the spectrum. In the case of broad bands, heights were taken from

the center of the peak. In cases where the Gaussian bands were distorted or

‘humped’ it was assumed that the broad peak actually represented two

combined peaks, and two peak measurements were made at the author’s

discretion.

25

94303

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411 462 513 565 616 667 719 770

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a

b

Figure 8. Relative intensities of peaks were manually calculated by drawing a background

line (a) across the spectrum. Peak heights were measured and calculated (b) from the background line.

Electron Probe Microanalysis (EPMA)

The Cameca SX50 electron microprobe at the University of

Massachusetts at Amherst’s Department of Geoscience was used to analyze

the major and minor element compositions of jadeite grains. Analyses were

done by Dr. M. Jercinovic. The accelerating voltage was 15 kV, the probe

current 20 nA, and the beam 5 µm in diameter. The counting time was 20 s on

each element except for Mg, Ca, Fe, and Mn – on which the count time was

240 s in order to maximize the measurement’s accuracy for calibration with

the LA ICP-MS instrumentation. A separate standard was run for each

element (Table 4). Grains were chosen for analysis based primarily on their

26

size and surface exposure (some grains were entirely buried under epoxy). A

total of six points were analyzed on each mount.

Element Standard Count time (sec)

Na Amelia Albite 20 Mg CrCats Syn. Diopside 240 Si PG721 Labradorite 20 Al PG721 Labradorite 20 K Sanidine (Leilen Kopf, Germany) 20 Ti TiO2 (Harford Co. Penn) 20 Ca CrCats Syn. Diopside 240 Fe Rockport Fayalite 240 Mn Rhodonite (Minas Gerais) 240 Cr 52-NL11 Chromite (Stillwater) 20

Table 4. Elements analyzed, and standards and count times used for EPMA analysis at

University of Massachusetts, Amherst.

Laser Ablated Inductively Coupled Plasma Mass-Spectrometry (LA ICP-MS)

LA ICP-MS uses high temperature plasma to ionize elements, which,

in this case, have been liberated from the jadeite grain mounts by laser

ablation. The ionized elements are then moved through the collector, and

separated by mass by a large magnet. A state-of-the-art magnetic field

regulator controls the changing of the magnetic field. The Finnigan Element-2

single-collector ICP-MS at the University of Maryland’s Isotope

Geochemistry Lab was used to determine the abundance of 30 minor and trace

elements, including most REE’s and hypothesized activators of luminescence

phenomena. Between 3 – 7 traverses of each grain mount were taken, with a

laser width of 80 – 100 µm. All results were calculated using Lotus 1-2-3

LAMTRACE software.

27

Mössbauer Spectroscopy

Mössbauer spectroscopy is a technique used to measure the resonant

absorption in solids using gamma-rays, which take the place of photons in a

sample. In short, the spectrometer consists of an oscillator, which moves the

radioactive source back and forth, perpendicular to the sample. This gives the

source a velocity, which in turn gives a range of energies to the gamma-rays.

Fe atoms in a sample will selectively absorb or transmit those photons,

yielding a spectrum of absorption vs. energy (velocity). Iron is one element

that is measured in Mössbauer spectroscopy, which distinguishes the ratio of

Fe2+/Fe3+. This element is important in CL because both valence states have a

significant influence on the emitted color of CL and the brightness of the

luminescence phenomena.

Samples were run in a WEB Research Co. model W100 spectrometer,

in front of the radioactive source 100-70mCi57Co in Rh. Each sample was run

at room temperature for 24 hours. Due to time constraints, samples could not

be run any longer. A 72 hour analysis period would have been ideal.

28

RESULTS

Cathodoluminescence Petrography Peak Identification: Summer 2005 Under CL, most green-luminescent

samples demonstrate homogeneous CL along idioblastic crystals, ranging in

length from 0.1 – 1.5 cm. Many jadeite grains exhibit strong oscillatory

zoning features on a scale of < 1 um (Figure 9). This type of zoning is an

indication of crystallization in a system that is far from equilibrium (Machel,

2000).

Figure 9. Example of oscillatory zoning in Guatemalan jadeitite sample 108369.

Additionally, crystallization sequences can be ascertained by CL. This

is well demonstrated by Japanese sample 112538 (Figure 10), which shows

29

evidence of partial resorption of red-CL jadeite, which is later overgrown by

bright-green luminescent rims.

Figure 10. Multiple crystallization sequences illuminated by CL. It is clear that the original grain, seen in the center and demonstrating pink CL, was partially reabsorbed and re-

crystallized under different conditions, as is demonstrated by the green CL rim. Guatemalan sample 112538.

These features provide an excellent example of CL’s utility, as they

are not easily observed under any other spectroscopic technique. During the

30

summer of 2005, 21 thin sections were analyzed for emission energies,

amounting to a total of 112 spectra. These samples were qualitatively assigned

to dull-green, bright-green, and mixed luminescence (Figure 11). Because

variation was seen at high magnification, the assignments were done

macroscopically by looking through the luminoscope window. Of these 21

samples, 17 demonstrated either dull- or bright-green luminescence. The

remaining samples demonstrated mixed luminescence colors.

A) Dull Green CL B) Bright Green CL Figure 11. Examples of different luminescence in jadeite. A) Dull Green CL as seen in Guatemalan sample MVE02SS2606. B) Bright Green Luminescence as seen in sample Guatemalan sample MVE02SS39A.

C) Red CL D) Blue CL Figure 11 (cont.) C) Red luminescence as seen in Californian sample J33C. D) Blue luminescence as seen in Burmese sample R3076. Scale on all photos: width of image = 1.6mm

31

Ten peaks were identified in the visible light spectrum, with the most

prominent absorptions occurring at 442 nm, 562 nm, 580 nm, and 682 nm

(Table 5A). The majority of samples demonstrated homogeneous green CL,

and, as expected, the overall peak positions of red and blue CL samples did

not appear to deviate much from the green samples’ positions.

Peak (nm) StDev (nm) n StdError Summer 2005 426 3.54 17 .86 Thin Sections 442 5.56 79 1.35 Total n: 112 453 1.74 14 .42 562 5.42 61 1.31 580 4.20 44 1.02 682 4.27 33 1.04 696 4.01 20 .97 722 6.89 8 1.67 739 5.59 19 1.36 779 4.69 23 1.14

Table 5a. Peak energies from thin section CL (‘Summer 2005’).

SEM CL – Summer 2005 Time allowed for 13 of the original 21 thin sections

to be analyzed and photographed under SEM CL. Results are strongly

influenced by the fact that the wavelength-range in SEM CL stretches well

into UV and IR light, beyond the wavelength range of conventional CL. This

instrument revealed an enormous amount of UV and IR light emitting from

these samples, and the scale dwarfed the visible light peaks observed in

regular CL, making it difficult to notice some of the visible blue, green, and

red features that are so easily distinguished under the other instrument.

Guatemalan sample 108369 demonstrates this well (Figure 12).

32

0.0

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12a 12b

Figure 12. SEM CL and corresponding spectrum (12a) and macroscopic CL and spectrum (12b) on Guatemalan sample 108369. The figure highlights the different wavelength ranges of

each instrument. The analysis point on the SEM image is marked by a red dot. The scale of this dot is approximately the size of the analysis diameter. The amount of IR coming off of

the jadeite samples is significantly larger than originally hypothesized (Götze, 2000) It is interesting to see that, even when the wavelength range of the SEM

spectrum is decreased to the visible spectrum (400 – 700 nm), the blue and red

peaks are not evident relative to the green peak’s intensity – a feature that was

visible in the regular CL (Figure 13). Regardless, it is clear that the

predominant visible light peaks observed are well expressed under both

instruments.

33

13a

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Figure 13. The scale of the SEM CL spectrum (a) is constrained to the same scale as seen in the conventional CL (b), it is evident that the intensity and position of the green peak is approximately the same, but that the noise interference in either instruments is

significantly different.

Grain Mount CL: Spring 2006 During January and March of 2006, 17 grain

mounts qualitatively assigned to dull-green, bright-green, red-, and blue-

34

luminescence were analyzed using CL. Nine samples of green CL were

chosen from the Summer 2005 sample list. Eight red and blue-luminescent

jades came from samples not previously used in this study. These red and blue

CL samples were added to the study in order to provide a more

comprehensive sample set, so we could compare dull green CL to all other

possible CL types (red, blue, and bright green). All samples were first

analyzed under the electron microprobe and LA ICP-MS for major, minor,

and trace element compositions. Damage to the grains from electron probe

and laser ablation is evidenced by ‘trenches,’ seen under transmitted light, and

a slight blurring of CL on the damaged section of the grain (Figure 14).

MVE04142

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Figure 14. Example of laser ablation damage on grain mount. Corresponding spectrum of jadeite sample MVE04142

shows that, despite damage, a strong peak is still emitted from the grain.

Due to time constraints, the grain mount analyses amounted to only 17 spectra

(one for each grain that had reliable chemical data). Among the spectra

35

36

collected, three predominant peaks were identified at 440 nm, 577 nm, and

680 nm (Table 5B). These correspond to the strongest peaks observed in the

summer 2005 thin section studies, suggesting that the minor surface roughness

in the grain mount polish and damage from previous chemical analyses did

not seriously interfere with the spectroscopic measurements.

Peak (nm) StDev (nm) n StdError Spring 2006 - - - - Grain Mounts 440 4.71 12 1.36 Total n: 17 - - - - - - - - 577 6.34 10 2.00 680 5.45 10 1.72 722 6.89 8 1.67 739 5.59 19 1.36 779 4.69 23 1.14

Table 5b. Peak energies from grain mounted jadeite suite (‘Spring 2006’).This data

demonstrates that, despite small sample size of Spring 2006 analysis, results fit into predominant peak positions of jadeite as determined during Summer 2005 (see Table 5a).

Variations are probably due to grain orientation and/or polarization effects.

Electron Microprobe Analysis A total of 21 jadeite grain mounts were analyzed under the electron

microprobe. Of these, four grains were poorly mounted (i.e. not enough

surface area was available for analysis), poorly polished (problems in

preparation), or yielded inconclusive results due to instrumental error. The

remaining 17 grains produced acceptable data (Table 6), accounting for 102

individual analyses.

37

MVE04142 01GSn211 MVE02SS2606 108369 01GSn15 MVJ90241 MVE02SS39A SS0416B 112538 BUR07 94303 J33C KB10JSS NBJ01 KB10J10 R3076 RGC4B

SiO2 58.19 58.00 58.34 57.88 58.45 67.78 59.08 58.29 58.82 59.91 59.49 59.41 58.54 59.77 59.43 59.30 59.24

Al2O3 24.32 22.68 20.93 20.89 24.04 19.67 23.23 25.57 24.30 25.27 25.86 25.69 24.76 24.78 22.06 25.46 25.32

TiO2 0.15 0.02 0.29 0.05 0.03 0.00 0.06 0.00 0.11 0.02 0.00 0.02 0.02 0.05 0.15 0.00 0.04 FeO(Moss) 0.71 1.29 1.00 0.71 0.42 0.00 0.43 0.10 0.48 0.07 0.01 0.13 0.25 0.06 0.31 0.12 0.11

Fe2O3(Moss) 0.58 0.92 0.81 0.38 0.25 0.00 0.20 0.22 0.50 0.07 0.00 0.05 0.43 0.04 0.25 0.06 0.23 MgO 0.71 1.01 2.32 2.96 0.86 0.00 1.14 0.25 0.48 0.16 0.02 0.01 0.48 0.51 2.27 0.21 0.22 MnO 0.03 0.07 0.04 0.06 0.04 0.00 0.02 0.01 0.04 0.00 0.02 0.02 0.01 0.00 0.01 0.01 0.01

Cr2O3 0.00 0.00 0.04 0.15 0.00 0.03 0.02 0.00 0.01 0.01 0.02 0.01 0.02 0.00 0.00 0.02 0.02 CaO 1.20 1.88 3.51 4.25 1.47 0.00 1.64 0.49 0.98 0.38 0.03 0.12 0.74 0.88 3.17 0.26 0.51

Na2O 14.69 14.08 13.07 12.59 14.10 12.00 14.13 14.88 14.38 14.80 15.22 15.03 14.63 14.53 13.13 14.94 14.76

K2O 0.00 0.00 0.01 0.00 0.01 0.04 0.01 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.01 0.01 FeO (EPMA) 1.23 2.11 1.73 1.05 0.64 0.00 0.61 0.30 0.93 0.13 0.01 0.17 0.64 0.09 0.53 0.17 0.32

Si 1.968 1.983 1.991 1.982 1.985 2.234 2.001 1.971 1.988 2.000 1.988 1.989 1.981 2.000 2.001 1.989 1.987 Al 0.969 0.914 0.842 0.843 0.963 0.764 0.927 1.019 0.968 0.995 1.019 1.014 0.987 0.977 0.876 1.007 1.001 Ti 0.004 0.001 0.008 0.001 0.001 0.000 0.002 0.000 0.003 0.000 0.000 0.000 0.000 0.001 0.004 0.000 0.001

Fe2+ 0.020 0.037 0.029 0.020 0.012 0.000 0.012 0.003 0.014 0.002 0.000 0.004 0.007 0.002 0.009 0.003 0.003 Fe3+ 0.015 0.024 0.021 0.010 0.006 0.000 0.005 0.006 0.013 0.002 0.000 0.001 0.011 0.001 0.006 0.001 0.006 Mg 0.036 0.051 0.118 0.151 0.043 0.000 0.058 0.012 0.024 0.008 0.001 0.000 0.024 0.025 0.114 0.010 0.011 Mn 0.001 0.002 0.001 0.002 0.001 0.000 0.001 0.000 0.001 0.000 0.001 0.001 0.000 0.000 0.000 0.000 0.000 Cr 0.000 0.000 0.001 0.004 0.000 0.001 0.001 0.000 0.000 0.000 0.001 0.000 0.001 0.000 0.000 0.000 0.001 Ca 0.043 0.069 0.129 0.156 0.054 0.000 0.060 0.018 0.036 0.014 0.001 0.004 0.027 0.031 0.114 0.009 0.018 Na 0.963 0.933 0.865 0.836 0.928 0.767 0.928 0.976 0.943 0.958 0.986 0.976 0.960 0.943 0.858 0.972 0.960 K 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.001 0.000 0.000 0.000

Total Cats 4.018 4.014 4.002 4.006 3.993 3.766 3.995 4.005 3.989 3.980 3.996 3.990 3.999 3.981 3.982 3.992 3.988

Table 6. Recalculated EPMA data showing major and minor element compositions for jadeite samples from Guatemala, Burma, Japan, and California.

Of the 17 grains, four demonstrated dull green CL, five demonstrated bright

green CL, four showed predominately red CL, and four showed overall blue

CL. The EPMA data were the foundation for final sample selection, as ICP-

MS could not be conducted without reliable EPMA results. Analyses were

recalculated with six oxygens in order to determine the precise mineral

formulae.

Results present a compositional (major and minor compounds and

elements) characterization of each sample. Despite the fact that 102 reliable

analyses were run over 17 samples, it was necessary to average the values,

since the other three spectroscopic (CL, ICP-MS, and Mössbauer) techniques

provided results that were based on bulk/full-grain samples of jadeite rock.

The compounds that show the most variance are SiO2, Na2O and Al2O3,

reflecting the overall abundance of those elements in jadeite. Overall, the

MnO, FeO, Cr2O3, and Ti2O3 contents of green CL are significantly higher

relative to red and blue luminescent jadeite. When dull green CL is compared

with bright green CL, an abundance of MnO, FeO, Cr2O3, and Ti2O3 is

observed in the former, suggesting that these compounds play a significant

role in the qualitative brightness of luminescence (Figures 15 – 17). Among

the other compounds analyzed under EPMA, the greatest variance is seen in

CaO – a component whose influence on CL is not well understood, and

conjectured to activate multiple peaks in the blue, green, and red wavelengths

(Gorobets and Rogojine, 2002).

38

Average Weight % MnO vs. CL Type

Dull Green

Bright Green

BlueRed

0.00

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Figure 15. Average MnO weight % by CL type.

Average Weight % Cr2O3 vs. CL Type

Dull Green

Bright Green Blue Red0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Aver

age

Wei

ght %

Cr 2

O3

Dull GreenBright Green

Blue

Red

Figure 16. Average Cr2O3 weight % by CL type.

Average Weight % FeO vs. CL Type

Dull Green

Bright GreenBlue

Red0.00

0.50

1.00

1.50

2.00

2.50

Aver

age

Wei

ght %

FeO Dull Green

Bright Green

Blue

Red

Figure 17. Average FeO weight % by CL type.

39

LA ICP-MS Analysis

A total of 125 ICP-MS analyses was conducted on the mounted jadeite

grains. Results show great variation in trace element abundances, particularly

in the REE elements (Table 7). Included in the analyzed elements were Dy,

Gd, Sm, and Tm – all hypothesized to play some part in luminescence

properties, although most of their energies have not yet been assigned to

specific jadeite features. In general, trace elements, including Fe+2 and Fe+3,

Cr+3 and most REE elements, are found in higher concentrations in dull green

CL than in bright green CL. Pb+2 and Eu+3 are the only elements that show

higher concentrations in bright green CL than in dull green CL, suggesting

that they may have a greater power in activating luminescence than the

combined effects of quenchers.

DULL GREEN CL Element (ppm) MVE04142 01GSn211 MVE02SS260 108369

Sm 0.076 0.581 0.237 0.177 Eu 0.062 0.147 0.096 0.158 Gd 0.146 0.540 0.222 0.267 Tb 0.030 0.134 0.044 0.064 Dy 0.239 1.334 0.212 0.440 Ho 0.076 0.437 0.046 0.108 Er 0.261 1.737 0.131 0.342 Tm 0.052 0.383 0.024 0.059 Yb 0.480 3.847 0.180 0.462 Lu 0.097 0.729 0.036 0.057 Pb 0.386 1.446 7.995 1.108 Th 0.385 1.599 0.168 0.014 U 0.431 2.503 0.289 0.066 Table 7. ICP-MS results, separated by CL type.

40

BRIGHT GREEN CL

Element (ppm) 01GSn15 MVJ90241 MVEO2SS39A SS0416B 112538

Sm 0.075 0.000 0.230 0.113 0.036 Eu 0.063 0.000 0.288 0.097 0.032 Gd 0.110 0.005 0.194 0.163 0.049 Tb 0.008 0.000 0.113 0.027 0.011 Dy 0.038 0.000 0.181 0.059 0.034 Ho 0.008 0.000 0.131 0.008 0.005 Er 0.024 0.000 0.166 0.020 0.017 Tm 0.008 0.000 0.063 0.015 0.025 Yb 0.053 0.000 0.286 0.079 0.028 Lu 0.024 0.000 0.128 0.008 0.012 Pb 0.820 0.000 3.116 0.231 0.847 Th 0.027 0.000 0.182 0.128 0.011 U 0.176 0.000 0.540 0.018 0.061 RED CL Element (ppm) BUR07 94303 J33C KB10JSS

Sm 0.047 0.012 0.032 0.070 Eu 0.024 0.009 0.028 0.027 Gd 0.064 0.028 0.073 0.110 Tb 0.007 0.000 0.012 0.009 Dy 0.028 0.030 0.018 0.047 Ho 0.007 0.001 0.008 0.012 Er 0.011 0.005 0.004 0.021 Tm 0.004 0.001 0.003 0.006 Yb 0.016 0.014 0.024 0.068 Lu 0.002 0.002 0.015 0.007 Pb 0.450 0.173 0.335 1.121 Th 0.050 0.006 0.005 0.075 U 0.042 0.020 0.027 0.084 Table 7 (continued). ICP-MS results, separated by CL type.

41

BLUE CL Element (ppm) NBJ01 KB10J10 R3076 RGC4B

Sm 0.112 0.177 0.117 0.026 Eu 0.023 0.168 0.073 0.068 Gd 0.160 0.506 0.098 0.177 Tb 0.003 0.039 0.006 0.011 Dy 0.027 0.185 0.065 0.014 Ho 0.013 0.076 0.007 0.003 Er 0.054 0.108 0.039 0.013 Tm 0.014 0.055 0.015 0.009 Yb 0.133 0.126 0.069 0.059 Lu 0.012 0.047 0.014 0.043 Pb 0.921 11.221 1.362 6.206 Th 0.104 0.328 0.048 0.030 U 0.200 0.381 0.357 0.028

Table 7 (continued). ICP-MS results, separated by CL type.

Mössbauer Spectroscopy Mossbauer analyses, which quantitatively distinguish between Fe+2

and Fe+3, show that dull green CL has an abundance of Fe+2. Dull green

jadeites contained an average of 0.93 ± 0.28 wt% FeO, while bright green

samples contained an average of 0.30 ± 0.21 wt% FeO. The average FeO and

Fe2O3 contents in red (0.11 ± 0.11 wt%) and blue (0.12 ± 0.13) luminescent

jadeites are far less than the total Fe found in green CL. Due to the

extraordinarily low Fe content in these minerals, it will be necessary to run

longer analyses (>72 hours) on these jadeites in order to refine the Fe+2/Fe+3

ratio results.

42

CL Sample Name FeO Fe2O3 % Fe3+

MVE04142 0.71 0.52 42.25 01GSn211 1.29 0.82 39.03 MVE02SS2606 1.00 0.73 42.12

Dul

l Gre

en

108369 0.71 0.34 32.13 01GSn15 0.42 0.23 35.24 MVJ90241 0.00 0.00 29.06 MVE02SS39A 0.43 0.18 30.07 SS0416B 0.17 0.13 42.25

Brig

ht G

reen

112538 0.48 0.45 48.39 BUR07 0.04 0.09 45.19 94303 0.13 0.00 0.00 J33C 0.02 0.15 24.70 R

ed

KB10JSS 0.26 0.39 60.63 NBJ01 0.06 0.03 36.89 KB10J10 0.31 0.23 42.25 R3076 0.02 0.15 30.18 B

lue

RGC4B 0.11 0.21 65.50 Table 8. Results from Mössbauer Spectroscopy, distinguishing Fe+2/Fe+3 by weight % values,

and total weight % Fe3+. Samples have been grouped by qualitative CL type.

43

DISCUSSION

Intensity Discrepancies Variations in absorption intensities of peaks in mineral standards

observed on the luminoscope do occur. It was our hope to determine an

appropriate way to correct for these intensity variations. However, no clear

patterns could be seen in the Summer 2005 CL analyses, and thus it was

concluded that such a correction would not be possible at this point. Intensity

fluctuations in CL have been shown to be affected by control of temperature

and analysis time on the overall intensity and peak position of a sample (i.e.

Balberg and Pankove, 1971; Pagel, 2000). When temperature is changed in a

systematic fashion, peaks and intensities will shift. Additionally, changes in

CL peak position and intensities are seen with an increase in the amount of

time that a sample has been run under CL. Most importantly, even though the

beam itself is not polarized, the orientation of a crystal grain plays a

significant role not only on the position of the CL peak, but also on the

amount of light that makes it out of the crystal upon interaction with the

energizing source (Marshall, 1988).

In order to limit the amount of variability that could be attributed to

intensity discrepancies, only the intensities from the grain-mounted jadeite

suite (‘Spring 2006 CL’) were used in the correlations. This decision ensured

that all samples were analyzed under identical conditions, with the same

thickness, glue, and polish. The thin sections from the NMNH were mounted

44

at unknown dates, and have undergone countless analyses, making them an

unadulterated proxy for intensity correlations. There is no significant

correlation between peak position and intensity, supporting the hypothesis that

the discrepancies in peak position are most strongly influenced by crystal

chemistry (Figure 18). This assumes that the uncontrolled crystal orientations

of the investigated jadeite grains are random.

Intensity vs. Wavelength

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

420 470 520 570 620 670

Wavelength (nm)

Inte

nsi

ty (

cou

nts

)

690 - 670

590 - 570

450 - 430

Figure 18. Relative intensity vs. peak position (nm), indicating that there is no apparent correlation between peak position and intensity. This suggests that, assuming random

orientation of crystals, the primary contribution to peak position is crystal chemistry – not crystallographic orientation.

To determine whether or not daily instrumental variability affected

these results, separate calculations for R2 and the significance of this figure

were conducted by date, where n = 11 on March 2nd, and n = 6 on March 3rd

45

(Table 9). Statistical analyses were run for both the full sample population and

sample populations by date.

DATE SAMPLE

NAME 108369 01GSn15 112538 BUR07 94303 J33C KB10JSS NBJ01 M

AR

CH

2nd

KB10J10 R3076 RGC4B MVE04142 01GSn211 MVE02SS2606 MVJ90241 MVE02SS39A M

AR

CH

3rd

SS0416B Table 9. Samples separated by date of CL analysis.

Contributions to Activation and Quenching of Jadeite CL

Preliminary analyses show that, even with a relatively small sample

size (n = 17), correlations can be drawn between the abundances of certain

elements and the intensity of luminescence peaks at 430 – 450 nm, 570 – 590

nm, and 670 – 690 nm (Table 10). Because the sample size for all analyses

was identical, R2 was first used as a measure of the relative predictive power

of the model. This value is defined by a metric between 0 and 1, where the

closer R2 is to unity (one) the better the model or the greater its ability to

predict accurate results.

46

Wavelength (nm)

Element/ Defect Center

435 – 450 nm Jadeite R2

570 – 590 nm Jadeite R2

670 – 690 nmJadeite R2

294 Pb2+ .050 .020 .048 355 Ce3+ .083 .014 .101 420 Eu3+ .013 .021 .161 450 Al3+ .209 .099 .377 480 Fe2+ .038 .065 .000 480 Ti4+ .228 .059 .375 490 Ni2+ Na Na Na 490 Ce3+ .083 .014 .101 550 - 640 Mn2+ .002 .231 .018686 - 700 Cr3+ .061 .061 .107 686 - 700 Fe3+ .001 .172 .007 Unknown Ca2+ .027 .191 .342Unknown REE .021 .070 .122Unknown Dy .027 .113 .133Unknown Gd .073 .048 .249Unknown Tm .020 .091 .103Quencher Fe2+ .038 .065 .000

Table 10. Proposed activators of luminescence (given in Table 1) and raw jadeite correlations, which include all samples including outliers (n = 17) (after Götze, 2000). When the populations-by-date are considered independently (i.e.

March 2nd is not directly compared to Mach 3rd data), it is evident that the R2

values and significance can again be used to interpret the relative contribution

of elemental abundance on luminescence (Table 11).

47

Wav

elen

gth

(nm

)

Ele

men

t

430–

450

nm

03/0

2

570

– 59

0 m

03

/02

670

– 69

0 m

03

/02

430

– 45

0 m

03

/03

570

– 59

0 m

03

/03

670

– 69

0 m

03

/03

294 Pb2+ .081 .017 .156 .065 .061 .041 355 Ce3+ .022 .135 .100 .041 .168 .003 420 Eu3+ .011 .16 .097 .099 .234 .000 450 Al3+ .048 .295 .347 .061 .192 .000 480 Fe2+ .004 .458 .115 .702 .303 .032 480 Ti4+ .075 .110 .325 .054 .512 .211 490 Ni2+ na na na na na na 490 Ce3+ .022 .135 .100 .041 .168 .003 550 - 640 Mn2+ .005 .432 .005 .051 .161 .337 686 - 700 Cr3+ .037 .124 .088 .162 .071 .103 686 - 700 Fe3+ .000 .314 .020 .385 .056 .369 Unknown Ca2+ .064 .240 .331 .499 .072 .653 Unknown REE .000 .171 .392 .011 .465 .145 Unknown Dy .016 .304 .097 .031 .287 .040 Unknown Gd .069 .036 .235 .018 .159 .009 Unknown Tm .004 .415 .107 .033 .227 .026 Quencher Fe2+ .004 .458 .115 .702 .303 .032

Table 11. Proposed activators of luminescence (given in Table 1) and jadeite correlations (R2) separated by date of analysis (after Götze, 2000). Where March 2nd n = 11 and March 3rd n = 6.

The correlations that were strong in both the full sample set and March

2nd sample set were investigated further, and significant outliers were removed

based on deviation from the mean of the full sample set in order to elucidate

the results (Table 12). The strength of correlations in March 3rd samples was

not considered when determining the elements that contribute most strongly to

luminescence phenomena in jadeite. In the case of this project, the small

sample population and relatively low R2 values must be considered as

evidence of multiple elements contributing to individual peaks. Further

clarification of each element and its relative effect on the intensity of the

48

green, blue, and red peaks observed in jadeite must incorporate a multivariate

analysis.

Proposed peak

Element 435 – 450 nm R2

570 – 590 nm

2

670 – 690 nm

2450 Al3+ .209 .295 (n = 11) .412 (n = 13)480 Ti4+ .320 (n = 12) .059 .443 (n = 12)550 - 640 Mn2+ .002 .655 (n = 8) .018 570 - 590 Ca2+ .027 .305 (n = 9) .342 570 - 590 Dy .027 .252 (n = 9) .247 (n = 10)686 - 700 Cr3+ .022 .107 .243 (n = 12)670 - 690 REE .021 .151 .392 (n = 11)670 - 690 Gd .194 (n = 15) .016 (n = 15) .249 670 - 690 Tm .163 (n = 11) .255 (n = 11) .264 (n = 13)

Table 12. Proposed activators of luminescence (given in Table 1) and final jadeite correlations. Sample population is n = 17, unless otherwise noted.

Blue Peak The intensity of blue (430 – 450 nm) luminescence is

correlated best with the activator Al3+ (R2 = .209, Figure 19). Abundances of

Ti4+ (R2 = .320, Figure 20) are negatively correlated with intensity, acting as a

quencher at this peak. It is likely that both of these elements are resting in the

M1 site coordination, similar to what has been proposed in feldspar (i.e.

Marfunin 1979, Rossman 2001). The effect of total REE abundance on blue

luminescence is relatively insignificant, although Gd and Tm abundances

show a very weak positive correlation with intensity.

49

Weight % Al2O3 at 430 - 450 nm

y = 0.0007x + 22.2R2 = 0.2085

20

21

22

23

24

25

26

27

0 1000 2000 3000 4000 5000 6000

Intensity from 430 - 450 nm

Al 2O

3 (w

t%)

Figure 19. Weight % Al2O3 vs. Intensity of blue peak (430 – 450 nm)

where n = 17 and R2 = 0.2085

Ti at 430 - 450 nm

R2 = 0.3202

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

0 1000 2000 3000 4000 5000 6000

Intensity from 430 - 450 nm

Ti (p

pm)

Figure 20. Abundance of Ti4+ (ppm) vs. Intensity of blue peak (430 – 450 nm)

where n = 12 and R2 = 0.320

Green Peak The strongest correlations of elemental abundance to the

intensity of the green peak (570 – 590 nm) are seen with Mn2+ (R2 = .655,

Figure 21), Ca2+ (R2 = .305, Figure 22), and the REE Dy (R2 = .252, Figure 23)

and Tm (R2 = .255, Figure 24).

50

Weight % MnO at 570 - 590 nm

R2 = 0.6546

0.0

0.00.0

0.0

0.00.0

0.0

0.0

0.00.0

0.1

0 1000 2000 3000 4000 5000 6000

Intensity from 570 - 590 nm

MnO

(wt%

)

Figure 21. Weight % of MnO vs. Intensity of green peak (570 – 590 nm) where n = 8 and R2 = 0.655

Weight % CaO at 570 - 590 nm

R2 = 0.3053

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1000 2000 3000 4000 5000 6000

Intensity from 570 - 590 nm

CaO

(wt%

)

Figure 22. Weight % of CaO vs. Intensity of green peak (570 – 590 nm) where n = 9 and R2 = 0.305

51

Dy at 570 - 590 nm

R2 = 0.252

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 500 1000 1500 2000 2500 3000 3500

Intensity from 570 - 590 nm

Dy

(ppm

)

Figure 23. Abundance of Dy (ppm) vs. Intensity of green peak (570 – 590 nm)

where n = 9 and R2 = 0.252

Tm at 570 - 590 nm

R2 = 0.2545

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 1000 2000 3000 4000 5000 6000

Intensity from 570 - 590 nm

Tm (p

pm)

Figure 24. Abundance of Tm (ppm) vs. Intensity of green peak (570 – 590 nm) where n = 11 and R2 = 0.255

52

The qualitative brightness of green CL is clearly influenced by the

abundance of Fe, where the average amount of iron in dull green samples (n =

4) is 1.53 ± 0.48 wt % FeO, while in bright green samples (n = 5), FeO is 0.50

± 0.36 wt % FeO on average (refer back to Figure 17). Fe2+ clearly plays a

role in quenching these minerals, as has been suggested in previous literature

(Machel, 2000). Even though the probe data do not accurately distinguish FeO

from Fe2O3, Mössbauer results indicate a strong relationship between Fe-type

versus qualitative assignment to either dull green or bright green CL. There is

no apparent relationship between intensity and FeO and Fe2O3 – indicating

that there is a difference between the intensity of light that is coming off of a

sample and the qualitative “brightness,” as observed by the operator through

the CL window.

Green CL jadeites tend to have a greater abundance of all trace

elements, including activators of red and blue CL (especially Al3+). This

indicates that the peaks of red and blue CL probably exist in the green CL

jadeites, but are masked by the greater intensity of green CL peaks. This is

also well demonstrated in the SEM CL spectra, where the intensity of UV and

IR peaks dwarf the appearance of the green peak. Due to the scale-

discrepancies in some cases of SEM spectra, visible light peaks were only

exposed when the data was limited to the visible light wavelengths.

Red Peak There are many elements that may contribute to red

luminescence in this data set. The most convincing correlations are seen with

53

the abundances of Al3+ (R2 = .412, Figure 25), Ti4+ (R2 = .443, Figure 26) Ca2+

(R2 = .342, Figure 27), and a combination of REE (R2 = .392, Figure 28),

especially the inclusion of Dy (R2 = .247), Tm (R2 = .264), and Gd (R2 = .249),

as has been previously suggested by Götze (2000).

Weight % Al2O3 at 670 - 690 nm

R2 = 0.4121

20

21

22

23

24

25

26

27

0 2000 4000 6000 8000 10000 12000 14000

Intensity from 670 - 690 nm

Al 2O

3 (w

t%)

Figure 25. Weight % of Al2O3 vs. Intensity of red peak (670 – 690 nm)

where n = 13 and R2 = 0.412

Ti at 670 - 680 nm

R2 = 0.4427

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

0 2000 4000 6000 8000 10000 12000 14000

Intensity from 670 - 680 nm

Ti (p

pm)

Figure 26. Abundance of Ti (ppm) vs. Intensity of red peak (670 – 690 nm)

where n = 12 and R2 = 0.443

54

Weight % CaO at 670 - 690 nm

R2 = 0.5874

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 2000 4000 6000 8000 10000 12000 14000

Intensity from 670 - 690 nm

CaO

(wt%

)

Figure 27. Weight % of CaO vs. Intensity of red peak (670 – 690 nm) where n = 9 and R2 = 0.587

REE at 670 - 690 nm

R2 = 0.3291

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 2000 4000 6000 8000 10000 12000 14000

Intensity from 670 - 690 nm

Tota

l REE

(ppm

)

Figure 28. Overall abundance of REE (ppm) vs. Intensity of red peak (670 – 690 nm)

where n = 10 and R2 = 0.329

The average Fe2O3 content in red CL (0.16 ± 0.16 wt%) is less than

half of that found in green CL (0.38 ± 0.28 wt% Fe2O3), suggesting that the

power that Fe2O3 plays in the activation of red CL is outweighed by other

factors in the crystal structure, such as the presence of elements described

55

above. The many elemental activators associated with the red peak’s intensity

suggest that this peak is actually a composite peak, consisting of many smaller,

and potentially indistinguishable, peaks. A multivariate analysis will elucidate

this hypothesis.

Future Work

Because this project is the first to combine these specific four

spectroscopic techniques, there are no previous research procedures to which

this study may be directly compared. Thus, in many ways, this is a project that

not only investigates the CL activators of a relatively uninvestigated mineral,

but also creates a foundation for future research that will incorporate similar

spectroscopic techniques.

Future work will focus on exploring the possibility of intensity

corrections with conventional CL, as the factors surrounding intensity

fluctuations are not well understood, despite the fact that they are

tremendously significant to our results. Additionally, we will make an attempt

at implementing a multivariate statistical analysis in order to assign a more

accurate significance to each element (or group of elements) and its influence

on peak intensities of jadeite.

56

CONCLUSION This study has shown that the CL spectra of jadeite from localities

around the world contain three identical peaks at 430-450 nm, 570 – 590 nm,

and 670 – 690 nm. The positions and intensities of these peaks may result

from the presence of Al3+, Ti4+, Ca2+, Mn2+, Fe2+/Fe3+, and REE, including Dy,

Gd, and Tm. This project contributes to the scientific community’s

understanding of these phenomena, especially as manifested in metamorphic

rocks and minerals. It is the first study that attempts to quantify the activators

of luminescence in jadeite. While the CL intensities (upon which the statistical

correlations are based) are uncorrected for the time-dependent intensity

variations, this study has attempted to minimize such variation by analyzing

grain mounts that were all constructed at the same lab, and all analyzed for CL

emission energies at the same time. The future implementation of a

multivariate analysis will constrain the variance that is currently seen in the

statistical results, and also take into account the roles that intensities of

individual peaks play upon one another within a sample.

57

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