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These six natural and synthetic rubies are typical of material that might be submitted to a gemological laboratory for identification. From top to bottom and left to right: 1.29 ct Kashan flux-grown synthetic ruby, 1.10 ct natural ruby, 0.93 ct Czochralski-pulled synthetic ruby, 0.95 ct Ramaura synthetic ruby, 1.05 ct natural ruby from Tanzania, and 0.57 ct Swarovski flame-fusion synthetic ruby with flux-induced fingerprints. The 1.10 ct natural ruby was reported to have come from Mogok, but trace-element chemistry indicated that the stone was from a basalt-hosted deposit (such as Thailand); microscopy also indicated a basaltic origin. Photo © GIA and Tino Hammid.
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Natural and synthetic gem rubies can be separated on the basis of their trace-element chemistry as determined by energy-dispersive X-ray fluorescence (EDXRF) spectrometry. This method is especially important for rubies that do not have diagnostic inclusions or growth features, since such stones are difficult to identify using traditional gem testin...
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... final step in the growth process is Czochralski pulling. We analyzed four TrueGem synthetic rubies (see, e.g., figure A-1, table A-1). These samples showed a composition that is different from any of the natural rubies we analyzed: Cr is high, and the absence of V combined with low Fe precludes natural origin. ...
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... our analyses, a concentration above 0.050 wt.% Ga 2 O 3 with some Fe, little or no Ti, and no V strongly indi- cates Douros as the source. When Ga is plotted together with V and Fe in a triangular diagram (fig- ure 10), further distinctions can be made. The trian- gular V-Fe-Ga diagram shows a ratio of these three elements, rather than their actual concentrations. ...
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... EDXRF data with these other techniques can help establish the geo- graphic origin of a sample. Our purpose here is to demonstrate how trace-element chemistry can help determine the geologic environment in which a nat- ural ruby formed, which is one step toward identify- ing its geographic source ( figure 11). ...
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... the formation conditions of basalt-hosted rubies are not well known, the compositions of associated minerals and mineral inclusions are consistent with the Fe- rich compositional trends measured in this study. In a triangular plot of V-Fe-Ga, the basalt-hosted rubies form a tight cluster at the Fe apex (i.e., high Fe, little or no Ga or V; figure 12). ...
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... was apparent in our samples. Rubies from Kenya plotted over a wide area of the V-Fe-Ga diagram ( figure 12). Two of the analyses overlapped with the field of marble-hosted rubies, while the remainder of the samples plotted in a dis- tinctive area closer to the Ga apex (i.e., Ga >Fe and Ga>V). ...
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... from basalt-hosted deposits typ- ically contained little V and moderate to high Fe. The opposite trends were seen in rubies from mar- Figure 11. In some gem markets, the geographic ori- gin is an important consid- eration toward its value. ...
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... here (clockwise from the left) are: a crystal from Mogok, Myanmar (Hixon ruby, 196.1 ct; specimen courtesy of the Los Angeles County Museum of Natural History, photo © Harold a & Erica Van Pelt), a 2.98 ct step cut from Thailand (photo © Tino Hammid), a round brilliant from Myanmar (stone courtesy of Amba Gem Corp., New York; photo © Tino Hammid), and an 8.33 ct oval brilliant from Sri Lanka (photo courtesy of ICA/Bart Curren). Figure 12. Natural rubies from different deposit types are plotted on this V-Fe-Ga diagram. ...
Citations
... A dark red grain has high Cr-values (2.1-2.2 wt %), a color-zoned grain with dark red rims and pale pink core passes from outer notably high Cr (3.2 wt %) to inner moderate Cr (0.2 wt %) contents and a pink grain has lower Cr (0.2-0.8 wt %) values. These ruby Cr contents are among the highest reported for Mogok rubies (LA-ICP-MS; 5,27) and in surveys of many natural/synthetic rubies (Proton Induced X-ray Emission (PIXE), Energy Dispersive X-ray Fluorescence (EDXRF), LA-ICP-MS) where the highest Cr values were <2 wt % [27][28][29][30][31][32][33][34][35]. Exceptionally high Cr contents, however, are known in some unusual ruby associations [36]. ...
... A dark red grain has high Cr-values (2.1-2.2 wt %), a color-zoned grain with dark red rims and pale pink core passes from outer notably high Cr (3.2 wt %) to inner moderate Cr (0.2 wt %) contents and a pink grain has lower Cr (0.2-0.8 wt %) values. These ruby Cr contents are among the highest reported for Mogok rubies (LA-ICP-MS; 5,27) and in surveys of many natural/synthetic rubies (Proton Induced X-ray Emission (PIXE), Energy Dispersive X-ray Fluorescence (EDXRF), LA-ICP-MS) where the highest Cr values were <2 wt % [27][28][29][30][31][32][33][34][35]. Exceptionally high Cr contents, however, are known in some unusual ruby associations [36]. ...
... Most Mogok and indeed SE Asian ruby genesis incorporate a metasomatic component during metamorphism of carbonate sequences which introduced the exotic trace element contents [8]. Some ruby also involves skarn metasomatic processes [1,5], although Ga enrichment is not a feature in most ruby [1,5,[27][28][29][30][31][32][33][34][35]. Analytical aberrations caused by elemental interference effects from the Si and Ca spikes appears unlikely and compensating for the elevated values would only increase Ga values. ...
MYANMAR-GEOLOGICAL-RESEARCH-REPORT-COLLECTION-for-the-Academic-BY-MYO-AUNG-EX-EXPLORATION-GEOLOGIST-THAILAND UPDATE 10 th August 2022
https://www.asiafinancial.com/china-rare-earth-miners-poisoning-northern-myanmar-report?utm_source=Klaviyo&utm_medium=email&utm_campaign=AF%20Daily%20-%20August%2010%20%28WYdYY5%29&utm_content=And%20China%20is%20now%20sourcing%20much%20of%20its%20heavy%20rare%20earths%20from%20a%20remote%20corner&_kx=6xSDRPqxY6gYPtf-VEvhz1f85F9A-uoBTLvFC6R6UJ8%3D.JGevqp
Rare Earths
China Rare Earth Mines ‘Poisoning’ Northern Myanmar – Report
August 10, 2022
Rare earth mines surged from a small number to “more than 2,700 mining collection pools at almost
300 separate locations over an area the size of Singapore,” Global Witness reported.
Locked crustal faults associated with the subducting Indian Lithosphere and its implications in
seismotectonic activity in the Central Indo-Burmese Ranges, Northeast India
January 2022
Geofizika Raghupratim RakshitDevojit BezbaruahFarha Zaman[...]Sowrav Saikia
Advances in Trace Element “Fingerprinting” of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar
Article-December 2014-Minerals
Frederick. Lin . SutherlandKhin ZawSebastien Meffre[...]Kyaw Thu
... The chemical information is a fundamental test for gemstones, cultural heritage, and archaeological sample identification and characterization. In fact, parallel to the main elements constituting the phases, the particular assemblage of trace elements (i.e., those present and their concentrations) provides a distinctive chemical signature for many gem materials [21,77]; therefore, different techniques can be considered. The first is Energy Dispersive X-ray Fluorescence (ED-XRF, or only XRF), due to its more straightforward applicability. ...
Featured Application: Based on the data and analytical methodologies reported here, this review can be used as a reference for Green Stones identification and characterization protocols. Moreover , due to the multidisciplinary approach discussed, it can also be considered as an example useful for similar applications.
Abstract: The present review aims to discuss the importance of a multidisciplinary approach in cultural heritage and archaeometry investigations. The analytical methods used to identify and characterize "Green Stones" are discussed as an example. In the present paper, the term Green Stones is applied but not limited to jade materials, which have considerable importance in cultural heritage studies. In fact, archaeological samples made in Green Stones have been discovered worldwide, with many dating back to the Neolithic Age. Moreover, these materials represent an interesting analytical challenge, starting with their nomenclature and, in most cases, the nature of their poly-crystalline samples and their heterogeneity. Indeed, after a brief introduction about the advantages of the non-destructive analytical techniques commonly used for gemstones and cultural heritage samples analyses, the limits of the same have been discussed on the basis of Green Stones applicability. Finally, a multidisciplinary methodology for Green Stones identification and full characterization , which considers materials' heterogeneity and information, has been proposed and based on different references.
... For example, particle-induced xray emission (PIXE) and energy-dispersive X-ray fluorescence (ED-XRF) analytical methods are applied to ruby and sapphire with the aim of obtaining their qualitative and quantitative chemical analyses and determining their provenance. The application of multivariate analysis on the PIXE data of ruby samples allowed the identification the trace elements V, Cr, Fe, Ti, and Ga [9,10]. The recent development of laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for trace element analysis in gems, although this technique causes marginal sample destruction [11,12]. ...
Laser-induced breakdown spectroscopy (LIBS), accompanied by chemometric data analysis, is used to identify and classify gemstones of various hardness. The study involves several gemstones: amethyst, aquamarine beryl, bloodstone citrine, diopside, and enstatite. Their hardness is determined through a correlation utilizing the spectral intensity ratio of the ionic to atomic spectral lines of an identified element in the LIB spectrum. The result of the relative hardness obtained from the LIBS analysis is in good agreement with the hardness measured from Mohs’s scale of hardness, a popular qualitative method to determine hardness. In this work, a linear relationship has been established between the Mohs’s hardness and the plasma excitation temperature. Thus, the hardness of the gemstones can be determined with the help of plasma excitation temperature. Moreover, the analysis of trace elements in LIB spectral data reveals that a particular element is responsible for the colors of gemstones. Therefore, the relative concentration of constituents is calculated for all gemstones and compared. Principal component analysis (PCA) is successfully applied to all gemstone spectra for rapid classification and discrimination based on their variable elemental concentrations and respective hardness.
... For discriminating corundum formed in different geological conditions, fingerprint characteristics of mineral inclusions can give some hints (e.g., Sutherland et al. 1998, Graham et al. 2008, Saminpanya & Sutherland 2011, Sorokina et al. 2017. However, trace elements such as V, Fe, Ga, and Cr are more often used (e.g., Muhlmeister et al. 1998, Calligaro et al. 1999. In other cases, Fe concentrations alone have been used to separate rubies from different types of deposits , Giuliani et al. 2020. ...
... In many cases, the provenance determination of marblehosted rubies remains difficult even in the gemological laboratory. Various discriminant plots using trace element contents and ratios have been employed to differentiate between rubies from different localities (e.g., Muhlmeister et al. 1998). Here, several discrimination schemes are used to compare our data with published LA-ICP-MS data from other marble-hosted deposits (Fig. 22). ...
Primary rubies in the Ailao Shan of Yunnan Province, China, are found in three layers of marble. However, the origin and source rocks of placer rubies in the Yuanjiang area remains unclear. Trace element geochemistry and inclusion mineralogy within these materials can provide information on their petrogenesis and original source. Zircon, rutile, mica group minerals, titanite, and apatite group minerals were the main solid inclusions identified within the placer Yuanjiang rubies, along with other mineral inclusions such as pyrite, pyrrhotite, plagioclase group minerals, and scapolite group minerals. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements showed that the placer rubies are characterized by average values of Mg (31 ppmw), Ti (97 ppmw), V (77 ppmw), Cr (3326 ppmw), Fe (71 ppmw), and Ga (66ppmw). A trace-element oxide diagram, Fe values (<350 ppmw), and the mineral inclusion assemblage suggest marble sources for the placer ruby. Therefore, the Yuanjiang rubies (both primary and placer) are metamorphic, and this fits well with the observations that skarn and related minerals are mostly absent in this deposit.
Yuanjiang rubies can be readily separated from the high-iron rubies of different geological types by their Fe content (<1000 ppmw). The discriminators Mg, Ga, Cr, V, Fe, and Ti have potential in separating Yuanjiang rubies from some other marble-hosted deposits, such as Snezhnoe. Nevertheless, geographic origin determination remains a challenge when considering the similarities in compositional features between the Yuanjiang rubies and rubies from some other marble-hosted deposits worldwide (e.g., Luc Yen). The presence of kaolinite group minerals and clusters of euhedral, prismatic zircon crystals in ruby suggest a Yuanjiang origin.
... In combination with gemological properties, it was possible to distinguish ruby and sapphire from different deposits worldwide. Trace element chemistry and isotope ratios are used frequently to determine the geographic origin of ruby and sapphire using binary or ternary discriminating plots or multivariate linear discriminant analysis (LDA) based on various analytical tools like LA-ICP-MS, portable X-ray fluorescence (XRF), energy-dispersive XRF (EDXRF), and thermal ionization mass spectrometry (TIMS) [50][51][52][53]. Besides trace element chemistry, UV-Vis-NIR spectroscopy, Raman spectroscopy, and the study of inclusion scenes are additional tools to determine the origin of blue sapphire [54]. ...
Growing public interest in getting information on the origin of raw materials used to manufacture goods for daily life has triggered the development of concepts to increase the transparency of raw material supply chains. Analytical proofs of origin (APOs) for raw materials may support those transparency concepts by giving evidence about the origin of a specific raw material shipment. For a variety of raw materials like gemstones, TTT (tantalum, tin, tungsten) minerals, and others, APOs have been developed. The identification of features that distinguish different origins, databases of those features from reliable reference samples, and a data evaluation strategy adopted to the envisaged application scenario are the key aspects of APO methods. Here, an overview is given on APO methods developed for different raw materials and application cases.
... Corundum (α-Al 2 O 3 ) is an important refractory mineral which forms in a large variety of natural environments ranging from the primitive solar system to the Earth lithosphere (e.g., Bowles et al., 2011). Natural gem-quality ruby and sapphire, whose color is related to Cr or Fe and Ti impurities, are emblematic corundum varieties of cultural and trading importance (e.g., Muhlmeister et al., 1998;Smith, 1995;Rossman, 2009). As a nominally anhydrous mineral, corundum is known to incorporate some amount of hydrogen under the form of structural OH groups, which are readily observed using infrared spectroscopy (e.g., Eigenmann and Günthard, 1971;Volynets et al., 1972;Beran, 1991;Smith, 1995;Wöhlecke and Kovács, 2001;Libowitzky and Beran, 2006). ...
... The models are consistent with those previously proposed by Phillips (1991, 1994), even though some details of the atomic-scale geometry may differ. Most likely, they also hold for natural samples, which always contain significant impurity concentrations (e.g., Muhlmeister et al., 1998) and display spectroscopic features similar to those of the doped synthetic samples (e.g., Beran, 1991;Smith, 1995;Beran and Rossman, 2006). ...
The atomic-scale structure, relative stability and infrared spectroscopic
properties of OH defects in corundum (α-Al2O3) are
theoretically investigated at the density functional theory level.
Comparison with experimental data makes it possible to assign most of the
narrow bands observed between 3150 and 3400 cm−1 in natural and Ti- or
V-doped synthetic corundum to specific defects. These defects correspond to
the association of one OH group with an Al vacancy and M4+ for
Al3+ substitutions in neighboring sites. The OH group is located in the
large oxygen triangle forming the base of the vacant Al site. Models of
interstitial proton associated with a nearby Mg2+ for Al3+
substitution are consistent with the broad band observed at 3010 cm−1
in Mg-doped corundum. Its is also suggested that two weaker OH-stretching
bands observed in nominally pure synthetic corundum at 3163 and 3209 cm−1 could be associated with intrinsic defects combining an Al and an
O vacancy. These results highlight the importance of defect clustering in
the high-temperature incorporation of hydrogen in nominally anhydrous
minerals.
... Red glass imitated in much cheaper price which is widely available and impacts on the ruby market in recent years. For this reason, many researchers (Juncomma et al., 2014;Sorokina et al., 2015;Muhlmeister et al., 1998;AokiNguyen, 1996) were studied the technique for identifying natural and imitation rubies on the basis of structural, trace-element chemistry, absorption and luminescence of the material. ...
In this work, the x-ray induced luminescence technique was used to investigate natural and imitation rubies. The red and pink natural rubies in the present work were provided from Myanmar and Vietnam, respectively. The imitation rubies (red and pink glasses) in glass were taken from imitation jewelry company in Thailand. Optical, compositional and structural were studies to confirm the identification of natural and imitation stone. X-ray diffraction (XRD) study reveals that natural rubies contain α-Al2O3 as the major phase. On the other hand, XRD does not show sharp peak for imitation ruby stone, therefore it indicates that the imitation rubies are made of amorphous material (glass). Absorption spectra in visible region of natural rubies, red and pink glasses show a prominent absorption band around 520–560 nm wavelength with Cr³⁺ transitions, gold nanoparticles and Er³⁺ transitions, respectively. Photoluminescence (PL) emission spectra of both natural rubies show strong red emission at 692 nm (λex = 577 nm), relating to Cr³⁺ transition (²Eg→⁴A2g). The green emission peak at 548 nm (λex = 403 nm) of imitation ruby (pink glass) was observed; it comes from the transition of Er³⁺ (⁴S3/2 → ⁴I15/2). The x-ray induced luminescence (XIL) spectra of natural rubies show similar pattern with PL result, while XIL of imitation rubies cannot be observed. This XIL result show the fast separation behavior between natural and imitation rubies. Therefore, XIL is suitable for using as a luminescence analysis of gemstones because of their fast process, non-destructiveness and without excitation wavelength special sample-preparation needs.
... Currently, the accurate chemical composition of rubies can be determined by several analytical techniques, such as X-ray fluorescence (XRF), electron microprobe analysis (EMPA), laser ablationinductively coupled plasma-mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Chemical data facilitate the differentiation between natural and synthetic rubies [67] ( Figure 15) and help to determine their geological origin worldwide [11,[68][69][70][71][72]. It is a multi-phase fluid inclusion containing a two-phase (liquid + vapor) CO 2 -H 2 S-S 8 -bearing fluid and minerals including diaspore (Dsp) and rutile (Rt). ...
... Currently, the accurate chemical composition of rubies can be determined by several analytical techniques, such as X-ray fluorescence (XRF), electron microprobe analysis (EMPA), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Chemical data facilitate the differentiation between natural and synthetic rubies [67] (Figure 15) and help to determine their geological origin worldwide [11,[68][69][70][71][72]. [47]: spiral growth, two-dimensional growth, and adhesive-type growth. ...
... Gallium (Ga)-vanadium (V)-iron (Fe) ternary showing the distinction between natural and synthetic rubies, modified from[67]. ...
Corundum is not uncommon on Earth but the gem varieties of ruby and sapphire are relatively rare. Gem corundum deposits are classified as primary and secondary deposits. Primary deposits contain corundum either in the rocks where it crystallized or as xenocrysts and xenoliths carried by magmas to the Earth’s surface. Classification systems for corundum deposits are based on different mineralogical and geological features. An up-to-date classification scheme for ruby deposits is described in the present paper. Ruby forms in mafic or felsic geological environments, or in metamorphosed carbonate platforms but it is always associated with rocks depleted in silica and enriched in alumina. Two major geological environments are favorable for the presence of ruby: (1) amphibolite to medium pressure granulite facies metamorphic belts and (2) alkaline basaltic volcanism in continental rifting environments. Primary ruby deposits formed from the Archean (2.71 Ga) in Greenland to the Pliocene (5 Ma) in Nepal. Secondary ruby deposits have formed at various times from the erosion of metamorphic belts (since the Precambrian) and alkali basalts (from the Cenozoic to the Quaternary). Primary ruby deposits are subdivided into two types based on their geological environment of formation: (Type I) magmatic-related and (Type II) metamorphic-related. Type I is characterized by two sub-types, specifically Type IA where xenocrysts or xenoliths of gem ruby of metamorphic (sometimes magmatic) origin are hosted by alkali basalts (Madagascar and others), and Type IB corresponding to xenocrysts of ruby in kimberlite (Democratic Republic of Congo). Type II also has two sub-types; metamorphic deposits sensu stricto (Type IIA) that formed in amphibolite to granulite facies environments, and metamorphic-metasomatic deposits (Type IIB) formed via high fluid–rock interaction and metasomatism. Secondary ruby deposits, i.e., placers are termed sedimentary-related (Type III). These placers are hosted in sedimentary rocks (soil, rudite, arenite, and silt) that formed via erosion, gravity effect, mechanical transport, and sedimentation along slopes or basins related to neotectonic motions and deformation.
... Corundum forms in mafic and siliceous geological environments, always associated with rocks depleted in silica and enriched in alumina, because in the presence of silica, Al will be preferentially incorporated into aluminosilicate minerals such as feldspars and micas [14]. Gem corundum is rare because it also requires the presence of Cr, Fe, and Ti to substitute for Al in the structure [9,15], and thermobarometric conditions favorable for its crystallization and stability [16,17]. Two major geological environments have been found to be favorable for the generation of gem-quality corundum; amphibolite-to medium pressure granulite-facies metamorphic belts and alkaline basaltic volcanism in continental rifting environments. ...
... Quantitative data for the most commonly observed elements in ruby and sapphire-Fe, Cr, Ti, V, and Ga-have been used by many authors (e.g., [8][9][10]15,33,59,60]) in attempts to determine gem corundum provenance. Figure 11 comprises a number of existing discrimination schemes, showing how our data compare with previously published data from the same localities. ...
... (a) Plot of Cr/Ga (ppm) versus Fe/Ti (ppm) (modified from [8]); fields are red = marbletype, black/dashed = Mong Hsu ruby [62], black = high Fe, and blue = blue sapphires. (b) Fe (ppm) versus Ga/Mg (ppm) (after [10]); (c) Mg × 100-Fe-Ti × 10 ternary plot modified after [10]; and (d) Fe-V-Ga ternary plot (after [15]), and (e) Fe/20-V × 3-Ga × 3 (after [28]) in gem corundum analyzed in this study. All data plotted are laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) values. ...
The geographic origin of gem corundum has emerged as one of its major value factors. Combined with gemological observations, trace element analysis is a powerful tool for the determination of corundum provenance. However, owing to similar properties and features of gem corundum from different localities, but similar geological settings, and very low levels of many trace elements in gem corundum, the determination of geographic origin remains challenging. In this study, we present trace elements compositions determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for rubies and blue sapphires from several different localities of geologically similar deposits: high-Fe amphibolite-type rubies, low-Fe marble-type rubies, and metamorphic blue sapphires. In addition, we determined Sr and Pb isotopic ratios by offline laser ablation sampling followed by thermal ionization mass spectroscopy (TIMS). By applying new and existing elemental discrimination schemes and the multivariate statistical method linear discriminant analysis (LDA), we show that, in addition to the commonly used discriminators Mg, Fe, V, Ti, and Ga, the elements Ni, Zr, Cr, and Zn show potential for geographic origin determination. Amphibolite-type rubies from different localities can be discriminated using Sr and Pb isotope ratios, whereas the discrimination of marble-type ruby and metamorphic blue sapphires is limited. Our results re-emphasize the challenge of geographic origin determination and the need for a more powerful discriminatory tool.
... Corundum (α-Al 2 O 3 ) is an important refractory mineral which forms in a large variety of natural environments ranging from the primitive solar system to the Earth lithosphere (e.g., Bowles et al., 2011). Natural gem-quality ruby and sapphire, whose color is related to Cr or Fe and Ti impurities, are emblematic corundum varieties of cultural and trading importance (e.g., Muhlmeister et al., 1998;Smith, 1995;Rossman, 2009). As a nominally anhydrous mineral, corundum is known to incorporate some amount of hydrogen under the form of structural OH groups, which are readily observed using infrared spectroscopy (e.g., Eigenmann and Günthard, 1971;Volynets et al., 1972;Beran, 1991;Smith, 1995;Wöhlecke and Kovács, 2001;Libowitzky and Beran, 2006). ...
... The models are consistent with those previously proposed by Phillips (1991, 1994), even though some details of the atomic-scale geometry may differ. Most likely, they also hold for natural samples, which always contain significant impurity concentrations (e.g., Muhlmeister et al., 1998) and display spectroscopic features similar to those of the doped synthetic samples (e.g., Beran, 1991;Smith, 1995;Beran and Rossman, 2006). Chemically complex Ti-bearing defects have previously been proposed as playing a role in the hydrogen speciation in olivine (Berry et al., 2005;Tollan et al., 2017) and diopside (Balan et al., 2020). ...
