Search Results (25)

Myanmar blue jadeite jade is a rare and highly prized gemstone, yet its coloration and formative mechanisms remain poorly understood. In this study, petrographic analysis, ultraviolet–visible (UV–Vis) spectroscopy, electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed on a sample of Myanmar blue jadeite with small white blocks to investigate its mineral composition, trace element distribution, and coloration mechanisms. Most of the sample was found to be blue, with surrounding white areas occurring in small ball-shaped blocks. The main mineral component in both the blue and white domains was jadeite. Although both areas underwent recrystallization, their textures differed significantly. The blue areas retained primary structural features within a medium- to fine-grained texture, reflecting relatively weaker recrystallization. The white areas, however, were recrystallized into a micro-grained texture, reflecting relatively stronger recrystallization, with the superimposed effects of external stress producing a fragmented appearance. The blue jadeite had relatively higher contents of Ti, Fe, Ca, and Mg, while the white jadeite contained compositions close to those of near-end-member jadeite. It was noted that, while white jadeite may have a high Ti content, its Fe content is low. UV–Vis spectra showed a broad absorption band at 610 nm associated with Fe²⁺-Ti⁴⁺ charge transfer and a gradually increasing absorption band starting at 480 nm related to V⁴⁺. Combining the chemical composition and the characteristics of the UV–Vis spectra, we infer that the blue coloration of jadeite is attributed to Fe²⁺-Ti⁴⁺ charge transfer; i.e., the presence of both Ti and Fe in blue jadeite plays a key role in its color formation. V⁴⁺ exhibited no significant linear correlation with the development of blue coloration. Prominent oscillatory zoning was observed in the jadeite, transitioning from NaAlSi₂O₆-dominant cores to Ca-Mg-Fe-Ti-enriched rims, reflecting the trend of fluid evolution during blue jadeite crystallization. Petrographic analysis indicated that the formation of the Myanmar blue jadeite occurred in two or three stages, with the blue regions forming earlier than the white regions. The blue jadeite also underwent significant recrystallization. Our findings contribute to the understanding of the formation of blue jadeite and the diversity of colors in jadeite jade. Full article

While existing studies on Guatemalan jadeite have predominantly focused on green varieties, the coloration mechanisms and origin of its blue counterparts remain poorly understood. Therefore, the present study provides the first comprehensive investigation of the Guatemalan blue jadeite using an integrated analytical approach, which combines Raman spectroscopy, micro X-ray fluorescence (µ-XRF), electron microprobe analysis (EMPA), X-ray diffraction (XRD), UV-Vis spectroscopy, and Cathodoluminescence (CL) imaging on seven representative samples. The results demonstrate that these jadeites consist of two distinct phases: a primary jadeite phase (NaAlSi₂O₆) and a secondary omphacite that form by metasomatic alteration by Mg-Ca-Fe-rich fluids. Spectroscopic analysis reveals that the blue coloration is primarily controlled by Fe³⁺ electronic transitions (with characteristic absorption at 381 nm and 437 nm) coupled with Fe²⁺-Ti⁴⁺ intervalence charge transfer, supported by μ-XRF mapping showing strong Fe-Ti spatial correlation with color intensity. CL imaging documents a multi-stage formation history involving initial high-pressure crystallization (Jd-I) followed by fluid-assisted recrystallization forming Jd-II and omphacite. The detection of CH₄, CO and H₂O in the fluid inclusions by Raman spectroscopy indicates formation in a serpentinization-related reducing environment, while distinct CL zoning patterns confirm a fluid-directed crystallization (P-type) origin. These findings not only clarify the chromogenic processes and petrogenesis of Guatemalan blue jadeite but also establish key diagnostic criteria for its identification, advancing our understanding of fluid-derived jadeite formation in subduction zone environments. Full article

Color is a primary determinant of the value of jadeite jade, but the petrological provenance of the chromogenic elements of jadeite jade remains uncertain. The characteristics of the associated chromite in Myanmar jadeite jade were systematically investigated through a series of tests, including polarized microscopy, microarea X-ray fluorescence spectroscopy (micro-XRF) mapping, electron probe microanalysis (EPMA), and backscattered electron (BSE) imaging. The results demonstrate that the chromite composition in Myanmar jadeite jade is characterized by a high concentration of Cr₂O₃ (46.18–67.11 wt.%), along with a notable abundance of MnO (1.68–9.13 wt.%) compared with the chromite from the adjacent Myitkyina peridotite. The diffusion of chromium (Cr) and manganese (Mn) in jadeite jade is accomplished by accompanying the metamorphic pathway of Mn-rich chromite → kosmochlor → chromian jadeite → jadeite. In the subsequent phase of jadeite jade formation, the chromium-rich omphacite veins generated by the fluid enriched in Ca and Mg along the fissures of kosmochlor and chromian jadeite play a role in the physical diffusion of Cr and Mn. The emergence of the lavender hue in jadeite is contingent upon the presence of a relatively high concentration of Mn (approximately 100–1000 ppmw) and the simultaneous absence of Cr, which would otherwise serve as a more effective chromophore (no Cr or up to a dozen ppmw). The distinctive Mn-rich chromite represents the primary origin of the chromogenic element Cr (green) and, perhaps more notably, an overlooked provider of Mn (lavender) in Myanmar jadeite jade. Full article

Chromite in the amphibolites of the Myanmar jadeite deposits has not been well studied. Mineralogical studies on chromite and related kosmochlor and Cr-omphacite in the amphibolite of the Myanmar jadeite deposits were conducted. Compared to the chromite in the adjacent serpentinized peridotite, the chromite had higher Cr₂O₃ (45.67–54.25 wt.%) and MnO (1.82–1.90 wt.%) but lower MgO (1.00–1.96 wt.%) and Al₂O₃ (1.05–15.09 wt.%), similar to the published chromite compositions in jadeitite. Serpentinite was derived from a highly depleted mantle peridotite. There were at least two stages of metasomatism during the transformation of serpentinite + chromite to magnesio-katophorite + chromite + thin kosmochlor (and/or Cr-omphacite cortex). The first stage was the Ca-rich metasomatism of serpentinite, resulting in sodic-calcic amphibole (magnesio-katophorite), which preceded the formation of jadeite. The second stage of Na-rich metasomatism was produced by the Na-Al-Si-rich fluids with the magnesio-katophorite + chromite (contemporaneous with the formation of jadeite). The composition of the fluid was altered by a reaction with magnesio-katophorite, increasing the Ca-Mg content and resulting in the formation of kosmochlor rich in Ca-Mg and/or peripheral Cr-omphacite. This kosmochlor–Cr-omphacite belongs to the Jd-Kos-Di ternary join, which differs from the kosmochlor–Cr-jadeite (which belongs to the Jd-Kos join in jadeitite). The formation of jadeitite with chromite + kosmochlor + Cr-jadeite occurs when large amounts of Na-Al-Si-rich fluids have wrapped the pieces of chromite-bearing amphibolite. This also explains the proverbial “moss spray green” given that amphibole (with chromite) brings out the green color in jadeitite. Full article

The geologic framework of western Washington, USA, is the result of collisional tectonics, where oceanic plate materials were subducted beneath the continental margin. As part of this process, fragments of mantle peridotites were transported into the upper crust along deep faults. The hydration of these ultramafic materials produced bodies of serpentinite. Subsequent regional metamorphism caused metasomatism of the serpentinite to produce a variety of minerals, which include nephrite jade, grossular, chlorite, diopside, vesuvianite, and pumpellyite. Many of the nephrite-bearing rocks are located along the Darrington–Devils Mountain Fault Zone in Skagit and Snohomish Counties. Intense prospecting has led to the establishment of many mining claims, but recreational collecting remains a popular activity. Full article

The jadeite jade in Guatemala exerts remarkable commercial quality, which has attracted wide attention. Guatemalan jadeite jade displays a rich variety of colors; however, the color formation of this jadeite jade has not been systematically investigated to date. In this paper, we study different colors of jade samples to trace the compositions and color-causing mechanisms through petrography, X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FTIR), laser Raman spectroscopy (LRS), and UV-visible absorption spectroscopy (UV-Vis), as well as electron probe microanalysis (EPMA). The results show that jadeite and omphacite are the main mineral compositions of Guatemalan jadeite jade, together with minor albite and other impurities. The color of Guatemala jadeite jade is mainly related to Cr³⁺, Fe²⁺, and Fe³⁺, of which a small amount of Cr³⁺ causes the jadeite jade to be emerald green. Moreover, 1~2% FeO contents can lead to the blue or gray color of the samples, while the Fe³⁺ makes the sample dark green. The green color of some Cr³⁺-free jadeite is caused by the electron transition between bands of Fe³⁺, and the green color is related to the iron content. Moreover, the chemical composition analysis shows that some metallic elements existed in Guatemalan jadeite jade, such as Ca, Ti, Al, Si, Ni, Fe, Mn, Cr, Na, Mg, and Sr, and some trace elements were lost or unevenly distributed, which may lead to the heterogeneity of the color of the samples. Our present investigation provides insights into color discrimination, quality evaluation, and identification of Guatemala jadeite jade. Full article

Melting phase relations of the diamond-forming olivine (Ol)–jadeite (Jd)–diopside (Di)–(Mg, Fe, Ca, Na)-carbonates (Carb)–(C-O-H-fluid) system are studied in experiments at 6.0 GPa in the polythermal Ol₇₄Carb_18.5(C-O-H)_7.5-Omp₇₄Carb_18.5(C-O-H)_7.5 section, where Ol = Fo₈₀Fa₂₀, Omp (omphacite) = Jd₆₂Di₃₈ and Carb = (MgCO₃)₂₅(FeCO₃)₂₅(CaCO₃)₂₅(Na₂CO₃)₂₅. The peritectic reaction of olivine and jadeite-bearing melts with formation of garnet has been determined as a physico-chemical mechanism of the ultrabasic–basic evolution of the diamond-forming system. During the process, the CO₂ component of the supercritical C-O-H-fluid can react with silicate components to form additional carbonates of Mg, Fe, Ca and Na. The solidus temperature of the diamond-forming system is lowered to 1000–1020 °C by the joint effect of the H₂O fluid and its carbonate constituents. The experimentally recognized peritectic mechanism of the ultrabasic–basic evolution of the diamond-forming system explains the origin of associated paragenetic inclusions of peridotite and eclogite minerals in diamonds, as well as the xenoliths of diamond-bearing peridotites and eclogites of kimberlitic deposits of diamond. Diamond-forming systems have formed with the use of material from upper mantle native peridotite rocks. In this case, the capacity of the rocks to initiate the peritectic reaction of olivine was transmitted with silicate components to diamond-forming systems. Full article

Fluorescence and phosphorescence are listed as mineral optical–physical properties in classical gemology textbooks. The trace elements which exist in gems, certain defects in the crystal lattice, and some luminous molecules contribute to luminescence phenomena in gem materials, including fluorescence and phosphorescence. A systematic luminescence study using an excitation-emission matrix (EEM) not only provides detailed information about the emission and excitation peaks, but also indicates the presence of specific trace elements, lattice defects, or luminous substances in gem materials. This provides reliable evidence for the characterization of gems. In this review paper, we briefly summarize luminescence spectroscopy and illustrate its applications in gem materials in our laboratory, including diamonds, fluorite, jadeite jade, hauyne, and amber. Meanwhile, this project is in process and needs more samples from reliable sources to confirm the described data. Full article

Unique finer-grained interstitial textures, occurring as small blocks or irregular shapes of 0.15–10 mm, were found merging in the coarse-grained textures of Kazakhstan jadeitite. According to the mineral content, the interstitial texture could be classified into two types: Type I, consisting of almost all jadeite crystals, minor omphacite, and little analcime, and Type II, comprising mainly omphacite and analcime, with minor jadeite crystals. They both showed no obvious preferred orientation and have distinct boundaries with the coarse-grained textures but appear more transparent, with finer grain sizes and higher degrees of idiomorphism. The coarse-grained textures include granitoid textures and radial clusters. The granitoid textures formed by euhedral to subhedral prismatic grains usually show rhythmic zoning patterns and parallel intergrowths. Furthermore, fluid inclusions contain H₂O and CH₄, and it was supposed that the coarse-grained textures were formed by the precipitation of jadeitic fluids. However, perhaps due to the insufficient supply of the fluids or sufficient space, some interspaces were left among the coarser-grained jadeitite. Afterward, these interspaces were filled with precipitation of the successor H₂O-richer fluids under a different P–T condition from that of the former coarser-grained jadeitite, and consequently, two kinds of interstitial textures formed. Such interstitial textures seem to appear only in Kazakhstan and therefore could serve as a typical visual identification feature of Kazakhstan jadeitite. Full article

Different jadeites have different characteristics. In this paper, the La-ICP-MS test is used to compare and analyze the elemental characteristics of jadeite in Guatemala and the Qing dynasty. The test results show that the highest value of Guatemalan jadeite Ca can reach 2.5 apfu, while the highest value of Qing dynasty jadeite is 0.73 apfu. The highest value of Na is the same for both. The concentration distribution range and highest value of Guatemalan jadeite and Qing dynasty jadeite Mg/(Mg + Fe) are the same. Guatemalan jadeite and Qing dynasty jadeite have a very wide content of trace elements. Qing dynasty Ca/(Mg + Fe) distribution is wider. Concentrations of Guatemalan and Qing dynasty jadeite Sr/Ba, which is a marine sediment, are greater than 1. The Ba in the Qing dynasty jadeite sediments contains a large amount of clay, resulting in higher levels than the average amount in Guatemalan jadeite Ba. The standard distribution map is similar, showing a “horn” shape. The Sr distribution is uneven. Guatemalan jadeite is heavily enriched in rare earths. Eu shows positive and negative abnormalities. The total rare earth value is 8.15 ppm. Qing Dynasty jadeite shows light rare earth enrichment, and Eu is a positive anomaly. The total rare earth value is 7.07 ppm. The characteristics of the two elements are somewhat similar, but different, which does not rule out the possibility that Qing dynasty jadeite came from Guatemala. Full article

Liquid immiscibility plays an important role in the formation of carbonatites and associated alkaline Si-undersaturated magmas. Experiments in the sodium carbonate-aluminosilicate systems suggest that the carbonate-silicate miscibility gap is limited by crustal and shallow mantle pressures (up to 2.5 GPa). Unlike in the potassium-rich carbonate-aluminosilicate systems, the carbonate-silicate miscibility gap was established at pressures of 3.5–6 GPa. It is therefore interesting to elucidate the immiscibility range under intermediate pressures, corresponding to 100–200 km depths. Here we conducted experiments over 3–6 GPa and 1050–1500 °C in the systems corresponding to immiscible melts obtained by partial melting of carbonated pelite (DG2) at 6 GPa and 1200 °C. We found that partial melting begins with the alkali-rich carbonatite melt, while immiscible phonolite melt appears over 1050–1200 °C at 3 GPa, 1200 °C at 4.5 GPa, and 1200–1500 °C at 6 GPa. As pressure decreases from 6 to 3 GPa, Na becomes less compatible, and the concentration of the jadeite component in clinopyroxene decreases by a factor of 1.5–6. As a result, the compositions of the immiscible phonolite and carbonatite melts evolve from ultrapotassic (K₂O/Na₂O weight ratio = 10–14) resembling silicic and carbonatitic micro-inclusions in diamonds from kimberlites and placers worldwide to moderately potassic (K₂O/Na₂O = 1–2), which may correspond to phonolitic and associated carbonatitic melts of the spinel facies of the shallow mantle. Full article

Identifying the origin of jadeite jades has become increasingly important from both mineral resource and metamorphic geology perspectives. In this study, we differentiate Myanmar gem-quality blue-water jadeite jades from their Guatemala counterparts via integrating various non-destructive spectrographic techniques, including X-ray fluorescence (XRF), Ultraviolet-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Our results show that the Myanmar blue-water jadeite jades are structurally homogenous with very few impurities, while their Guatemala counterparts commonly have a yellowish margin with scattered white albite and disseminated greenish inclusions of omphacite and (minor) aegirine-augite. Geochemically, the UV absorption spectral data indicate that the Guatemala samples have higher total Fe and Fe²⁺ contents, but lower Fe³⁺ content than the Myanmar samples. The Guatemala samples also have higher omphacite content (lower molar Na/(Na+Ca) ratio, as reflected by the lower IR absorption peak wavenumber) and higher heterogeneity (as reflected by the ~680 cm⁻¹ Raman peak shift difference) than that from Myanmar. Major differences are also discovered in the blue series (Myanmar: 0–0.7 cm⁻¹; Guatemala: 1.7–3.2 cm⁻¹) and blue-green series (Myanmar: 6.9 cm⁻¹; Guatemala 13.7 cm⁻¹) of the Raman peak shift difference, which altogether can provide a novel, nondestructive method for distinguishing blue-water jadeite jades from different origins. Full article

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 polycrystalline 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. Full article

Myanmar is the principal provider country of high-quality jadeite jade in the world, including so-called primary and secondary stones. The secondary stones occur as rounded pebbles, boulders, and blocks in eluvium–alluvium and often hold varying degrees of weathering. Unlike common rocks, such as granite, gabbro, schist, gneiss, and amphibolite, secondary jadeite stones frequently have weathered cortexes that vary in appearance, depth, texture, and mineral components compared with those of inner primary bodies. In this study, representative samples of secondary eluvial–deluvial jadeite stones with varying weathered cortexes were selected, and their appearances, textures, mineral components, and chemical composition features were analyzed. Their weathered cortexes were red, yellow, white, or black, and were 0.01–1.80 cm thick. The cortexes were opaque, often with soil luster and a fansha phenomenon. The body of the jade was usually translucent, and green and white in color. Along the border between the weathered cortex and the body of a certain jade stone, the textures were the same for the successive grain sizes. The only difference was that there were more cracks, cleavage planes, and fissures in the cortex. Jadeite was the main mineral component of both; however, minor late-stage supergene minerals (such as gibbsite, kaolinite, and halloysite) and Fe-bearing colloidal minerals were identified along the grain boundaries in the cortex. Studies of the textures and mineral components of weathered cortexes have gemmological applications including the identification and grading raw jadeite, as well as its design and carving. Moreover, such studies might provide information for improving our understanding of the unique weathering processes of monomineralic aggregates relative to multiple-mineral rocks, as well as gambling jadeite jade pieces through analyzing their cortex. Full article

Because of the increasing price of jadeite, many fake species have appeared on the market. We recognized three pieces of fake black jadeite that had been placed among real black jadeite. In this study we conducted a mineralogical investigation of the three fakes and the real jadeite by using FTIR and XRD techniques; in addition, we performed in situ major, minor and trace element chemical characterization based on EPMA-WDS and LA-ICP-MS techniques. The three imitations have different components, dominated by katophorite (97%), augite (66%) and anorthite (97%). In contrast, the real jadeite sample contains more than 99% jadeite. Unlike previous reports on black jadeite, the dark omphacite exsolution around the jadeite cleavage is the chromogenic factor in the present study, whereas the black color of the imitations comes from light absorption by major melanocratic minerals and widespread fine graphite. We propose that 2–4 sharp bands between 600 and 800 cm⁻¹ of FTIR and the 2.42 and 2.49 Å peaks of XRD can be used to discriminate black jadeite from imitations. Even though natural jadeite deposits are being exhausted, materials of the three natural imitations were determined not to be suitable for jewelry due to low hardness, widespread occurrence and unknown injury of the radioactive elements thorium and uranium. Otherwise, they could enhance value and be ideal for large-sized ornaments of fine design. Full article