Search Results (16)

This work targets a knowledge gap in the high-pressure decomposition of methanol, complementing prior moderate-pressure diamond anvil studies below 4 GPa and hyperbaric-pressure laser chemical vapour deposition (HP-LCVD) experiments below 0.01 GPa. Localised decomposition of methanol into various carbon allotropes was investigated at pressures of up to 15 GPa. Diamond anvil cell (DAC) pressures were monitored in real-time using ruby fluorescence and a high-resolution spectrometer. Selective saser reactive synthesis within diamond anvil cells (LRS-DAC) was achieved using a 20-micron 1/e² laser beam focus—one order of magnitude smaller than the diamond anvil chamber dimensions. Confocal Raman spectroscopy and electron microscopy were employed to investigate the deposit’s local microstructure. Various carbon allotropes were synthesised selectively, including single-crystal diamond, nanocrystalline diamond, multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), and amorphous carbons. At least two unknown Raman signatures were observed and unlikely to be harmonics or combinations of ordinary Raman peaks, the closest known Raman spectra being that of catechol and polycatechol. Potential side reactions are proposed, where polymerisation and/or ring-formation may occur during high-pressure moderate-temperature (HPMT) conditions. Full article

This paper presents the construction of an innovative high-temperature sensor based on the optical principle. The sensor is designed especially for the measurement of exhaust gases with a temperature range of up to +850 °C. The methodology is based on two principles-luminescence and dark body radiation. The core of this study is the description of sensing element construction together with electronics and the system of photodiode dark current compensation. An advantage of this optical-based system is its immunity to strong magnetic fields. This study also discusses results achieved and further steps. The solution is covered by a European Patent. Full article

Spinel is a precious stone with a long history. In ancient societies spinel was considered to be an imitation of ruby. With the depletion of ruby mineral resources, gem—grade spinel has attracted more and more attention from consumers. In the last decade, as the popularity of spinel in the global colored gem market continues to rise, plenty of domestic and foreign jewelry brands have launched spinel based jewelry. This study takes spinels from Burma, Vietnam, Sri Lanka, and Tanzania as its research objects and performs a series of tests to obtain their gemological characteristics, spectral characteristics, and chemical composition, with the aim of comparing the differences between spinels with different colors from different areas and exploring the chromogenic mechanism of spinels. Only Burmese red spinels have a typical Cr spectrum. The types of inclusions and the contents of trace elements are the main differences between spinels from the four areas. Burmese spinel is characterized by an octahedral negative crystal filled with dolomite or a mixture of dolomite and calcite. Magnesite is present in Sri Lankan spinels, and dolomite is present in Tanzanian spinel. Dislocation systems and the presence of titanite and talc inclusions are strongly indicative features of Vietnamese spinel. Sri Lankan spinel is characterized by abundant gas–liquid inclusions, such as the beaded healing fissure. The trace element contents of the four areas are different. Burmese spinel is poor in Fe and Zn (Fe: 135.68–3925 ppm; Zn: 338.58–1312 ppm), while Burmese red spinel is rich in Cr (up to 7387 ppm). Vietnamese spinel is rich in Fe (3669.63–19,425 ppm) and poor in Ti content (<89 ppm), while Tanzanian spinel is rich in Zn (5129.96–7008 ppm). High content of Cr + V can lead to the red color in spinel, and the contents of Cr and V change obviously with color. Spinels appear red when Cr content is higher than V, while spinels appear orange when V content is higher than Cr. The red, pink, and orange spinels are colored by Cr³⁺ and V³⁺, showing a wide absorption band centered at 400 nm and 550 nm. Fe plays a dominant role in purple spinels. The purple spinel is colored by Fe³⁺ and Fe²⁺. Full article

The geographic origin determination of ruby is increasingly important in the gem trade and geological research. Unlike metamorphic-related ruby, the rarer basalt-related ruby has gained significant attention, especially from Thailand, a major producer of such gems. Thai rubies are classified as magmatic-related origin rubies, which can be found as xenocrysts (xenoliths) hosted by alkali basalts. This paper focuses on the gemological characteristics, inclusion morphology, identification, and geochemistry of basalt-hosted ruby from the Chanthaburi-Trat area in Thailand. Various instruments, including gemological conventional ones, Raman Spectrometer, EPMA, and LA-ICP-MS were used for the analysis. This study aimed to identify the distinctive characteristics of rubies from Thailand and find feasible methods for their geographic origin determination, in comparison with rubies from Cambodia, Myanmar, and Mozambique. Thailand samples exhibit diverse inclusion scenes and contain a variety of crystal or mineral inclusions. Raman spectroscopy results indicate the presence of anorthite, titanium oxide, and gypsum inclusions. The main chemical composition of the ruby consists of Al₂O₃, with trace elements including Fe, Cr, Si, Mg, Ti, Ga, V, Ca, and Ni. The color of Thailand ruby is correlated with the content of Cr and Fe. Chemical diagrams illustrating the contents of Fe, Mg, Cr, V, Ti, and Ga offer reasonable discrimination tools for differentiating rubies from various deposit types. The chemical compositions and inclusion characteristics of rubies from Thailand serve as reliable indicators for their origin identification. This study is an advantageous supplement to the research on Thailand rubies. Full article

The mRubyFT is a monomeric genetically encoded fluorescent timer based on the mRuby2 fluorescent protein, which is characterized by the complete maturation of the blue form with the subsequent conversion to the red one. It has higher brightness in mammalian cells and higher photostability compared with other fluorescent timers. A high-resolution structure is a known characteristic of the mRubyFT with the red form chromophore, but structural details of its blue form remain obscure. In order to obtain insight into this, we obtained an S148I variant of the mRubyFT (mRubyFT^S148I) with the blocked over time blue form of the chromophore. X-ray data at a 1.8 Å resolution allowed us to propose a chromophore conformation and its interactions with the neighboring residues. The imidazolidinone moiety of the chromophore is completely matured, being a conjugated π-system. The methine bridge is not oxidized in the blue form bringing flexibility to the phenolic moiety that manifests itself in poor electron density. Integration of these data with the results of molecular dynamic simulation disclosed that the OH group of the phenolic moiety forms a hydrogen bond with the side chain of the T163 residue. A detailed comparison of mRubyFT^S148I with other available structures of the blue form of fluorescent proteins, Blue102 and mTagBFP, revealed a number of characteristic differences. Molecular dynamic simulations with the combined quantum mechanic/molecular mechanic potentials demonstrated that the blue form exists in two protonation states, anion and zwitterion, both sharing enolate tautomeric forms of the C=C–O⁻ fragment. These two forms have similar excitation energies, as evaluated by calculations. Finally, excited state molecular dynamic simulations showed that excitation of the chromophore in both protonation states leads to the same anionic fluorescent state. The data obtained shed light on the structural features and spectral properties of the blue form of the mRubyFT timer. Full article

True genetically encoded monomeric fluorescent timers (tFTs) change their fluorescent color as a result of the complete transition of the blue form into the red form over time. Tandem FTs (tdFTs) change their color as a consequence of the fast and slow independent maturation of two forms with different colors. However, tFTs are limited to derivatives of the mCherry and mRuby red fluorescent proteins and have low brightness and photostability. The number of tdFTs is also limited, and there are no blue-to-red or green-to-far-red tdFTs. tFTs and tdFTs have not previously been directly compared. Here, we engineered novel blue-to-red tFTs, called TagFT and mTagFT, which were derived from the TagRFP protein. The main spectral and timing characteristics of the TagFT and mTagFT timers were determined in vitro. The brightnesses and photoconversions of the TagFT and mTagFT tFTs were characterized in live mammalian cells. The engineered split version of the TagFT timer matured in mammalian cells at 37 °C and allowed the detection of interactions between two proteins. The TagFT timer under the control of the minimal arc promoter, successfully visualized immediate-early gene induction in neuronal cultures. We also developed and optimized green-to-far-red and blue-to-red tdFTs, named mNeptusFT and mTsFT, which were based on mNeptune-sfGFP and mTagBFP2-mScarlet fusion proteins, respectively. We developed the FucciFT2 system based on the TagFT-hCdt1-100/mNeptusFT2-hGeminin combination, which could visualize the transitions between the G1 and S/G2/M phases of the cell cycle with better resolution than the conventional Fucci system because of the fluorescent color changes of the timers over time in different phases of the cell cycle. Finally, we determined the X-ray crystal structure of the mTagFT timer and analyzed it using directed mutagenesis. Full article

The chemical composition and spectra of untreated and heat-treated rubies from Mozambique and Madagascar were analyzed by an electron probe microscopy analysis, laser ablation inductively coupled plasma quadrupole mass spectrometry, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-visible spectroscopy. Due to the different content of Fe and different inclusions, rubies from Madagascar belong to alkaline basalt deposit, while rubies from Mozambique belong to amphibole metamorphic rock. The ruby samples were heated to 900 °C to change their color. As Fe and Ti ions can be transferred into different valences and diffused into the interior of rubies, Cr ions in cracks or cleavages entered the crystal lattice during heat treatment and the content of Fe and Ti decreased, while the content of Cr increased in heat-treated rubies. After heating, blue-purple decreased and the red hue increased, while the blue color band disappeared and yellow appeared in the cracks of the samples because of the chemical changes. Compared with untreated rubies, the infrared absorption peaks of 2123 cm⁻¹ and 1990 cm⁻¹ related to inclusions disappeared, and the existence of 3236 cm⁻¹ and 3186 cm⁻¹ absorption peaks was a typical characteristic of heat-treated ruby, which was produced by changes in its inclusion. In addition, due to the weakened charge transfer of Fe²⁺ and Ti⁴⁺ and the increasing reaction of Fe²⁺ → Fe³⁺ along with the heat treatment, the UV-visible absorption peak at 400 nm shifted to purple. Full article

Raman spectra of fluid inclusions in gem rubies from Yuanjiang deposit (China) within the Ailao Shan-Red River (ASRR) metamorphic belt showed the presence of compounds such as CO₂, COS, CH₄, H₂S, and elemental sulfur (S₈), accompanied by two bands at approximately 2499 and 2570 cm⁻¹. These two frequencies could be assigned to the vibrations of disulfane (H₂S₂). This is the second case of the sulfane-bearing fluid inclusions in geological samples reported, followed by the first in quartzite from Bastar Craton of India. The H₂S₂ was likely in situ enclosed by the host rubies rather than a reaction product that formed during the cooling of H₂S and S₈, suggesting sulfanes are stable at elevated temperatures (e.g., >600 °C). By comparing the lithologies and metamorphic conditions of these two sulfane-bearing cases (Bastar and Yuanjiang), it is suggested that amphibolite facies metamorphism of sedimentary sequence that deposited in a continental platform setting might favor the generation of sulfanes. Sulfanes may play an important role in the mobilization of Cr that is essential for ruby crystallization. Full article

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. Full article

The red variety of corundum owes its color and strong fluorescence to the presence of Cr, as well as traces of Fe. The latter can reduce the fluorescence and thus impact the appearance of the final gem. Gem quality rubies are rarely available for scientific study and even less common in their rough form. Opaque inclusions in rubies are often removed during faceting and remain unidentified. This study aims to identify opaque inclusions in rubies from the two most common origins seen in the high end market today: Mogok, Myanmar and Montepuez, Mozambique. Using electron probe microanalaysis (EPMA) the inclusions were identified as sphalerite and pyrrhotite in Mogok rubies. The paragenesis of Myanmar, marble-related rubies is fairly well understood and no Fe-rich minerals apart from sulfides have been identified. Opaque inclusions in Mozambican rubies are a complex mix of Fe-Cu-Ni sulfides with exsolution textures. These inclusions are interpreted to be small amounts of sulfide melt trapped during corundum formation. The different sulfide phases crystallized from this entrapped melt and some phases experienced later exsolution during cooling. The formation of amphibole-related, Mozambican rubies is not well understood, but it is obvious that very different processes are at work compared to the marble-related Myanmar ruby deposits. Full article

The Snezhnoe ruby deposit is located in the Muzkol–Rangkul anticlinorium within the Cimmerian zone of the Central Pamir. On the local scale, the deposit occurs on discrete relict bedding planes of calcitic marbles belonging to the Sarydzhilgin suite. Four ruby-bearing mineral assemblages are present within the main parts of the deposit: (1) scapolite + phlogopite + muscovite + margarite; (2) plagioclase + muscovite + margarite; (3) muscovite + phlogopite + margarite; (4) calcite. The ruby + calcite association is the most economically important, whereas the association of plagioclase + scapolite + phlogopite + muscovite is typical for the ruby-free parts of the deposit. Mica group minerals with a distinctive green color due to enhanced Cr and V concentrations are the main prospecting indicators for the ruby mineralization. The oxygen isotopic composition of the rubies is +15.3‰, a common value for crustal metamorphic and sedimentary rocks. The ratios of indicative trace elements in the rubies are Ga/Mg < 8.2, Fe/Mg < 51.2, Cr/Ga > 6.9 and Fe/Ti < 31.6. These values are characteristic for metamorphic corundum. The bulk ruby-bearing rocks have an initial ⁸⁷Sr/⁸⁶Sr ratio of ~0.70791 and εNd of ~−9.6, also pointing to the crustal origin of the deposit in agreement with the geological data. Ancient Al-enriched sediments are suggested to be a possible protolith for the ruby-bearing rocks. The temperature of the metamorphic processes was estimated at 760 ± 30 °C using Zr-in-rutile geothermometry. Raman mapping of rutile inclusions trapped within the ruby crystal indicates that the minimum pressure of mineralization was about one kilobar. The age determined by the Rb–Sr thermal ionization mass spectrometry of phlogopite, plagioclase and bulk rock is 23 ± 1.6 Ma, corresponding to the timing of relaxation after peak metamorphism during the Alpine–Himalayan Orogeny. Full article

The results of the study of eskolaite associated with marble-hosted ruby found for the first time in the Kuchinskoe occurrence (Southern Urals) are presented. Here, eskolaite was located on the surface and near-surface regions of ruby crystals. Eskolaite diagnostics was confirmed by powder X-ray diffraction (URS-55). The morphology and chemical composition of eskolaite and associated ruby was studied using a JSM-6390LV scanning electron microscope and a Cameca SX 100 electron probe microanalyzer. The eskolaite crystals were hexagonal and tabular, up to 0.2 mm in size. Ruby mineralization was formed during prograde and retrograde dynamothermal metamorphism. The eskolaite associated with the prograde stage ruby contained Al₂O₃ (9.1–23.62 wt %), TiO₂ (0.52–9.66 wt %), V₂O₃ (0.53–1.54 wt %), FeO (0.03–0.1 wt %), MgO (0.05–0.24 wt %), and SiO₂ (0.1–0.21 wt %). The eskolaite associated with the retrograde stage ruby was distinguished by a sharp depletion in Ti and contained Al₂O₃ (12.25–21.2 wt %), TiO₂ (0.01–0.07 wt %), V₂O₃ (0.32–1.62 wt %), FeO (0.01–0.08 wt %), MgO (0.0–0.48 wt %), and SiO₂ (0.01–0.1 wt %). The associated rubies contained almost equal amounts of Cr₂O₃ (2.36–2.69 wt %) and were almost free from admixtures. The identification of the eskolaite associated with the marble-hosted rubies from the Kuchinskoe occurrence is a new argument in favor of introduction of Al and Cr into the mineral formation zone. The mineralization was localized in the metamorphic frame of the granite gneiss domes and was formed synchronously with them. Full article

Dosimetry is a widespread material science field dealing with detection and quantification of ionizing radiation using electronic processes in materials. One of the main aspects that determines the performance of dosimeters is the type of defects the material contains. Crystalline lattice imperfections are formed around impurity ions, which may have a smaller or larger size, or different oxidation states compared to host ions. In this study, we show what effects Cr impurities have on the luminescent properties of alumina. Porous ${\mathrm{Al}}_2{\mathrm{O}}_3:\mathrm{Cr}$ microceramics synthesized using the sol-gel method showed a higher thermoluminescence response than a single crystal ruby. We have found that ${\mathrm{Cr}}_2{\mathrm{O}}_3$ concentration of 0.2 wt% was optimal; it yielded the highest X-ray luminescence and thermostimulated luminescence readout of all studied additive concentrations added to alumina during synthesis. Our results show that Cr doped alumina could potentially be used as a promising new material for dosimetry of ionizing radiation. Full article

Greece contains several gem corundum deposits set within diverse geological settings, mostly within the Rhodope (Xanthi and Drama areas) and Attico-Cycladic (Naxos and Ikaria islands) tectono-metamorphic units. In the Xanthi area, the sapphire (pink, blue to purple) deposits are stratiform, occurring within marble layers alternating with amphibolites. Deep red rubies in the Paranesti-Drama area are restricted to boudinaged lenses of Al-rich metapyroxenites alternating with amphibolites and gneisses. Both occurrences are oriented parallel to the ultra-high pressure/high pressure (UHP/HP) Nestos suture zone. On central Naxos Island, colored sapphires are associated with desilicated granite pegmatites intruding ultramafic lithologies (plumasites), occurring either within the pegmatites themselves or associated metasomatic reaction zones. In contrast, on southern Naxos and Ikaria Islands, blue sapphires occur in extensional fissures within Mesozoic metabauxites hosted in marbles. Mineral inclusions in corundums are in equilibrium and/or postdate corundum crystallization and comprise: spinel and pargasite (Paranesti), spinel, zircon (Xanthi), margarite, zircon, apatite, diaspore, phlogopite and chlorite (Naxos) and chloritoid, ilmenite, hematite, ulvospinel, rutile and zircon (Ikaria). The main chromophore elements within the Greek corundums show a wide range in concentration: the Fe contents vary from (average values) 1099 ppm in the blue sapphires of Xanthi, 424 ppm in the pink sapphires of Xanthi, 2654 ppm for Paranesti rubies, 4326 ppm for the Ikaria sapphires, 3706 for southern Naxos blue sapphires, 4777 for purple and 3301 for pink sapphire from Naxos plumasite, and finally 4677 to 1532 for blue to colorless sapphires from Naxos plumasites, respectively. The Ti concentrations (average values) are very low in rubies from Paranesti (41 ppm), with values of 2871 ppm and 509 in the blue and pink sapphires of Xanthi, respectively, of 1263 ppm for the Ikaria blue sapphires, and 520 ppm, 181 ppm in Naxos purple, pink sapphires, respectively. The blue to colorless sapphires from Naxos plumasites contain 1944 to 264 ppm Ti, respectively. The very high Ti contents of the Xanthi blue sapphires may reflect submicroscopic rutile inclusions. The Cr (average values) ranges from 4 to 691 ppm in the blue, purple and pink colored corundums from Naxos plumasite, is quite fixed (222 ppm) for Ikaria sapphires, ranges from 90 to 297 ppm in the blue and pink sapphires from Xanthi, reaches 9142 ppm in the corundums of Paranesti, with highest values of 15,347 ppm in deep red colored varieties. Each occurrence has both unique mineral assemblage and trace element chemistry (with variable Fe/Mg, Ga/Mg, Ga/Cr and Fe/Ti ratios). Additionally, oxygen isotope compositions confirm their geological typology, i.e., with, respectively δ¹⁸O of 4.9 ± 0.2‰ for sapphire in plumasite, 20.5‰ for sapphire in marble and 1‰ for ruby in mafics. The fluid inclusions study evidenced water free CO₂ dominant fluids with traces of CH₄ or N₂, and low CO₂ densities (0.46 and 0.67 g/cm³), which were probably trapped after the metamorphic peak. The Paranesti, Xanthi and central Naxos corundum deposits can be classified as metamorphic sensu stricto (s.s.) and metasomatic, respectively, those from southern Naxos and Ikaria display atypical magmatic signature indicating a hydrothermal origin. Greek corundums are characterized by wide color variation, homogeneity of the color hues, and transparency, and can be considered as potential gemstones. Full article

Ruby in diverse geological settings leaves petrogenetic clues, in its zoning, inclusions, trace elements and oxygen isotope values. Rock-hosted and isolated crystals are compared from Myanmar, SE Asia, and New South Wales, East Australia. Myanmar ruby typifies metasomatized and metamorphic settings, while East Australian ruby xenocrysts are derived from basalts that tapped underlying fold belts. The respective suites include homogeneous ruby; bi-colored inner (violet blue) and outer (red) zoned ruby; ruby-sapphirine-spinel composites; pink to red grains and multi-zoned crystals of red-pink-white-violet (core to rim). Ruby ages were determined by using U-Pb isotopes in titanite inclusions (Thurein Taung; 32.4 Ma) and zircon inclusions (Mong Hsu; 23.9 Ma) and basalt dating in NSW, >60–40 Ma. Trace element oxide plots suggest marble sources for Thurein Taung and Mong Hsu ruby and ultramafic-mafic sources for Mong Hsu (dark cores). NSW rubies suggest metasomatic (Barrington Tops), ultramafic to mafic (Macquarie River) and metasomatic-magmatic (New England) sources. A previous study showed that Cr/Ga vs. Fe/(V + Ti) plots separate Mong Hsu ruby from other ruby fields, but did not test Mogok ruby. Thurein Taung ruby, tested here, plotted separately to Mong Hsu ruby. A Fe-Ga/Mg diagram splits ruby suites into various fields (Ga/Mg < 3), except for magmatic input into rare Mogok and Australian ruby (Ga/Mg > 6). The diverse results emphasize ruby’s potential for geographic typing. Full article