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Article

Mineralogical, Gemological Characteristics and Petrogenesis of High-Quality Maw-Sit-Sit Jade from the Myanmar Jade Belt

by
Yu Zhang
,
Guanghai Shi
* and
Jiabao Wen
School of Gemmology, China University of Geosciences (Beijing), Beijing 100083, China
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(11), 983; https://doi.org/10.3390/cryst15110983
Submission received: 14 October 2025 / Revised: 7 November 2025 / Accepted: 12 November 2025 / Published: 14 November 2025
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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Abstract

Maw-sit-sit jade resembles kosmochlor-jadeitite in appearance and is spatially associated with it in the Myanmar Jade Belt. However, the mineral composition, microstructure, and petrogenesis of this type of jade remain unclear. To address this gap, this study investigated high-quality Maw-sit-sit jade using a range of analytical techniques, including conventional gemological tests, infrared spectroscopy, petrographic observations, electron probe microanalysis (EPMA), and backscattered electron (BSE) imaging. Results show that Maw-sit-sit jade primarily consists of albite and chromium-omphacite, with minor amphibole (eckermannite and richterite). Jadeite and relict chromite are absent in the studied samples. Its high albite content gives it lower refractive index (RI: 1.55–1.56) and specific gravity (SG: 2.69–2.73) compared to kosmochlor-jadeitite and jadeite jade. Additionally, Maw-sit-sit jade exhibits punctate or banded fluorescence under ultraviolet (UV) light, distinguishing it from kosmochlor-jadeitite and jadeite jade (both inert). Petrographically, euhedral albite fills interstices between early-formed Cr-omphacite and eckermannite, which is textural evidence of its late-stage origin. Eckermannite and Cr-omphacite occur as enclosed grains with embayed boundaries and dissolution pores, indicating they experienced mechanical disruption and chemical dissolution during subsequent geological processes. Petrogenetically, Maw-sit-sit jade (defined as “Cr-omphacite-albitite”) forms via a two-stage process: (1) Under high-pressure/low-temperature (HP/LT) conditions in the subduction zone, Na-Al-Si-rich fluids metasomatize chromite-bearing serpentinite protoliths, generating an early assemblage of jadeite, Cr-omphacite and amphiboles; (2) During subsequent plate exhumation and decompression, jadeite underwent retrograde metamorphism under low-pressure/low-temperature (LP/LT) conditions involving residual Na-Al-Si fluids, resulting in the formation of albite. This process led to the replacement of early-formed minerals by euhedral albite, ultimately generating the Ab+Cr-Omp+Eck symplectic texture. This study elucidates the mineralogical, gemological identity and petrogenesis of high-quality Maw-sit-sit jade, advancing our understanding of fluid evolution within a subduction zone.

1. Introduction

Myanmar Jade Belt (near Hpakan, Kachin State, northern Myanmar) is world famous for producing high-quality jadeite jade [1,2]. Jadeite jades (or jadeitites) are among the most valuable and popular varieties of jade. They consist predominantly of jadeite or other sodic (-calcic) clinopyroxenes (e.g., omphacite and kosmochlor), together with minor amphibole, albite, and chromite, which is collectively called feicui in Chinese [3]. Jadeite jade is known for its abundance of colors, among which the green variety is rare, popular, and highly valued. However, in addition to green jadeite jade, the Myanmar Jade Belt also produces a unique green jade known locally and in China as Maw-sit-sit jade, which is found in a village called Sit-sit, a few kilometres north of Tawmaw. It is very similar to green jadeitite with a high kosmochlor content. In 1965, the gemologist Gübelin named it “Maw-sit-sit” after the place where it was found, i.e., the mine in the village of Sit-sit [4].
The mineralogical composition of Maw-sit-sit jade remains unclear. Different researchers have reported a number of components. Gübelin (1965) posited that the Maw-sit-sit rock is not jadeite jade but rather a rock composed primarily of fine-grained albite, with the presence of Cr-bearing jadeite [4]. As stated by Hänni and Meyer (1997), chromite, kosmochlor and chromium amphibole have been identified as the dominant, well-developed minerals, with minor of zeolite, chlorite, albite and serpentine also present [5]. Colombo et al. (2000) reported the compositions of albite, kosmochlor, chromite, chromium-containing eckermannite and natrolite in the Maw-sit-sit rock [6]. Additionally, Nyunt (2009) identified a rock type in the Tawmaw region that exhibited similarities in appearance to the Maw-sit-sit rock [7]. The mineralogical composition and concentration of major minerals may vary between different samples of this rock, but it is essentially composed entirely of kosmochlor and amphibole, with little or no albite [8]. The Maw-sit-sit rock may retain relict chromite or may be free of chromite, with only kosmochlor and other minerals remaining. The prevailing opinion is that the Maw-sit-sit rock is a green rock, typically composed of chromium-jadeite-kosmochlor, albite, sodium amphibole, clinochlore, natrolite, and chromite. It has been identified as a minor unit in amphibolites [6,7,9,10,11].
Throughout human history, rocks with aesthetically pleasing forms have frequently been utilized and adorned as jade. The green and high-quality Maw-sit-sit jade exhibits a similar appearance to that of green jadeite jade and is often sold as a kind of jade that imitates the latter. The mineralogical composition of Maw-sit-sit jade is highly variable, and the microstructure, comparison of gemological characteristics with that of jadeite jade, and petrogenesis remain unclear. Meanwhile, Maw-sit-sit jade, as an associated rock of Myanmar jadeite, exhibits scarcity in production, and acquiring samples is challenging, which hinders systematic research. This study focuses on the mineralogical and gemological characteristics of high-quality Maw-sit-sit jade from Myanmar Jade Belt, exploring the petrogenesis of Maw-sit-sit jade.

2. Geological Setting

The Myanmar Jade Belt, also known as the Myanmar jadeite deposits, is a tectonic zone related to subduction formed by the Mesozoic-Cenozoic subduction of the Eastern Indian Plate beneath the Burmese Plate [2,12,13,14]. The presence of enriched Na-Al-Si fluids in this zone, combined with high-pressure/low-temperature (HP/LT) metamorphic conditions, creates a favorable environment for the formation of jadeite and Maw-sit-sit jade [1,15]. The Myanmar Jade Belt is centered in the Pharkant-Tawmaw region of Kachin State in northern Myanmar. Maw-sit-sit jade samples were sourced from the Maw Sit Sit vein, located northwest of Namshamaw town (Figure 1).
The key geological units in this region include serpentinite mélanges (the primary host rock for jadeitite and Maw-sit-sit jade), high-pressure, low-temperature (HP/LT) metamorphic rocks (e.g., eclogite and blueschist), and ophiolitic peridotites [1].

3. Materials and Methods

3.1. Sample Selection and Preparation

In this study, two Maw-sit-sit jades from the Myanmar Jade Belt (in Pharkant-Tawmaw of the Kachin State) were selected for analysis. Their appearance was very similar to that of green jadeitite with a high content of chromium-omphacite (Figure 2). Two samples were observed to be cabochons, displaying an uneven bright green, mixed with white and spotty black green.
All samples were cut one piece from the bottom and prepared as polished rock thin sections of approximately 0.03 mm for microstructural observation, electron probe microanalysis (EPMA) testing and backscattered electron (BSE) imaging.

3.2. Methods

The refractive index of the samples was determined with the distant vision technique on a Gem-A refractometer (manufacturer: The Gemological Association of Great Britain, London, UK). The specific gravity of the samples was determined by the hydrostatic method using an electronic balance of model JE1103CE (manufacturer: Mettler Toledo, Zurich, Switzerland). Each sample was measured three times and the mean values of these parameters were reported. The sample’s external characteristics were observed under a GI-M2S6E gemological microscope. The fluorescence properties were examined using a GI-UVB ultraviolet (UV) lamp, equipped with two light sources: a long-wavelength of 365 nm and a short-wavelength of 253.7 nm. The manufacturer of the gemological microscope and UV lamp is Nanjing Baoguang Testing Technology Co., Ltd., Nanjing, China.
Petrographic observation used an Olympus BX51/DP71 polarizing microscope at the Laboratory of the School of Gemology, China University of Geosciences (Beijing). Rock thin sections were observed under a polarizing microscope to characterize the optical properties of constituent minerals, determine mineral contents, analyze textures, and establish paragenetic sequences.
Electron probe microanalysis (EPMA) was performed using a JEOL JXA-8100 electron probe microanalyzer (EPMA) (manufacturer: Japan Electronics Corporation, Tokyo, Japan). The analysis conditions include 15 kV acceleration voltage, 2 × 10−8 A beam current and 1 μm beam diameter. Raw data were processed with the PRZ (a correction method for quantitative analysis), and natural and artificial minerals were analyzed as standard materials. Backscattered electron (BSE) images on the spatial distribution of different minerals were also obtained.
The EPMA and BSE analyses were conducted at the State Key Laboratory of Continental Dynamics, Institute of Geology, Chinese Academy of Geological Sciences. All other testing and analysis were performed at the Gemology Experimental Teaching Center of the China University of Geosciences (Beijing).

4. Results

4.1. Gemological Characteristics

The samples exhibit a fine-grained texture. The white portion of the sample is composed of albite, which exhibits slight transparency. The green portion and small dark green spots have been identified as Cr-omphacite and amphibole, respectively. The samples are the mixture of materials with different hardnesses. The surface characteristics of the sample were observed under a gemological microscope, which revealed the presence of “undercutting” effect caused by differences in mineral hardness [16]. The external microscopic characteristics of the samples are shown in Figure 3.
The refractive indices (RI) of the 2 samples are in the range of 1.55~1.56, and the specific gravities are in the range of 2.69~2.73. The broad range of refractive indices and specific gravities observed can be attributed to the high degree of heterogeneity present within the sample.
The albite present in the Maw-sit-sit jade exhibits a fluorescent reaction when exposed to ultraviolet (UV) lamps, resulting in the display of punctate or banded fluorescence. The fluorescence observed under short-wavelength (SW) ultraviolet light, characterized by a medium blue-white hue, is more pronounced in comparison to that observed under long-wavelength (LW) ultraviolet light, which manifests a weaker intensity (Table 1).

4.2. Petrography

Mineralogically, albite and Cr-omphacite are the main constituent minerals. Sample X2 consists of approximately 55 vol.% albite, 40 vol.% Cr-omphacite, and an additional 5 vol.% amphibole. In contrast, sample X5 comprises around 65 vol.% albite, 30 vol.% Cr-omphacite, and 5 vol.% amphibole.
The albite exhibits equigranular granoblastic texture, with most grains being euhedral or subhedral and a particle size range of 10 to 200 μm. Under plane-polarized light, albite is colorless, while under cross-polarized light, it exhibits grayish to yellowish interference colors (Figure 4).
In some jadeitites with a high kosmochlor or Cr-omphacite content, kosmochlor or Cr-omphacite exhibits a intense green color under both plane-polarized and cross-polarized light. In contrast, in the samples examined in this study, or Cr-omphacite displayed a dark green-gray color under both plane-polarized and cross-polarized light (Figure 5). Its grain size is relatively fine, ranging from a few microns to approximately 20 μm. In samples X2 and X5, Cr-omphacite occurs as discrete, fragmented grains embedded within an equigranular granoblastic matrix dominated by albite. The Cr-omphacite exhibits embayed grain boundaries and forms symplectic intergrowth with albite (Figure 5e,f, Figure 6a–c and Figure 7a,b). These textural features provide direct evidence of metasomatic replacement.
The relatively high interference color (blue to violet) of amphibole facilitates its identification under a cross-polarized light. Two distinct amphibole minerals were identified in the samples: eckermannite (Eck) and richterite (Rct). Generally, both exhibit a pale green hue under plane-polarized light. Eckermannite is more abundant, characterized by an anhedral morphology (Figure 5a–d). Internally, it displays distinct cleavage planes, with fractured boundaries preferentially developed along these cleavage directions (Figure 5a,b and Figure 7d). In contrast, richterite occurs sporadically in minor quantities, typically displaying prismatic or acicular habits with grain sizes ranging from tens of microns up to approximately 100 μm or larger (Figure 5a,b). Furthermore, richterite grains exhibit oscillatory zoning patterns in the BSE images (Figure 6c,d) and reflected light photomicrographs (Figure 7c).
Several zircons were detected in sample X2. These zircon crystals are small, with sizes ranging from a few microns to a dozen microns. In the BSE image, zircon can be identified by its high-relief form and bright white BSE signal. Zircons are severely altered, with their original crystal structure being partially replaced. This alteration results in porous domains, embayed edges, and a pseudomorph that retains the morphology of the primary zircon but lacks its crystalline integrity (Figure 6c,d).
Notably, jadeite was not detected in the Maw-sit-sit jade samples analyzed in the present study.

4.3. Mineral Chemistry

The chemical composition and atomic formula of albites, Cr-omphacites and amphiboles in Maw-sit-sit jade of Myanmar origin are presented in Table 2, Table 3 and Table 4.
Compared with the kosmochlor in jadeitite and amphibolite, the Cr-omphacite in our samples is distinguished by lower Cr2O3 (11.01–13.21 wt.%), lower Al2O3 (4.57–5.07 wt.%), higher CaO (4.99–5.93 wt.%), higher MgO (3.72–4.72 wt.%), and higher TFeO (5.21–5.62 wt.%).
The albite matrix is white, highly pure, and free of chromium, with minimal impurity elements. Trace chromium was detected in albite adjacent to Cr-omphacite, with concentrations reaching up to 1.37 wt%. This Cr is derived from Cr-omphacite inclusions rather than structural substitution. The extremely fine-grained symplectic intergrowth of Cr-omphacite and albite results in some analytical spots inadvertently encompassing Cr-omphacite, thereby elevating the measured Cr content in albite.
Amphiboles (Table 3) in the samples usually contain measurable amounts of chromium. Eckermannite (Eck) exhibits an anhedral morphology and contains 3.57 wt% Cr2O3. Moreover, richterite (Rct) exhibits prismatic, coarse-grained crystals with a preferred orientation, and its Cr2O3 content ranges from 2.91 to 4.77 wt%. The amphiboles are symbiotically associated with albite and Cr-omphacite, collectively forming symplectites (Figure 7b).
The zircon crystals are small, with sizes ranging from a few microns to a dozen microns. Two analysis points (designated X2-45 and X2-53) were analyzed via X-ray spectroscopy, and the data are presented in Table 5. Calculations confirm that both X2-45 and X2-53 correspond to zircon (ZrSiO4).

5. Discussion

5.1. Composition Characteristics of Cr-Omphacite in Maw-Sit-Sit Jade

Pyroxenes are silicate minerals characterized by a single-chain silica-oxygen framework structure and the general chemical formula XY[Si2O6], where X corresponds to the M2 site and Y to the M1 site. When the M2 site is dominated by large-radius cations such as Ca and Na, etc., the mineral is classified as clinopyroxene. The primary mineral constituent of jadeite jade is jadeite (Jd: NaAl [Si2O6]), which is a hard and dense clinopyroxene formed under high-pressure/low-temperature (HP/LT) conditions (5–11 kbar, 150–400 °C) [1,18]. Other pyroxenes associated with jadeite jade include kosmochlor (Kos: NaCrSi2O6) and omphacite (Omp: (Ca,Na) (Mg,Fe2+,Al)Si2O6). Omphacite consists of a solid solution of jadeite (Jd) and diopside (Di: CaMgSi2O6), with minor amounts of hedenbergite (Hd: CaFe2+Si2O6) and aegirine (Aeg: NaFe3+Si2O6) [3,19,20,21,22]. These pyroxenes typically belong to solid solution series, where both isovalent substitutions, such as Al3+ ↔ Cr3+, and coupled substitutions, such as Na+ + Al3+ ↔ Ca2+ + (Mg2+ + Fe2+), are common occurrences. No miscibility gap exists in the Jd-Kos binary system or the Di-Kos-Jd ternary join [23]. Therefore, it is necessary to plot the compositions on the Quad (Wo (Wollastonite) + En (Enstatite) + Fs (ferrosilite))-Jd(jadeite)-Aeg(aegirine) ternary classification diagram to determine the specific mineral designation (Figure 8) [24]. Since both jadeite and kosmochlor fall within the jadeite field on this ternary diagram, samples with a kosmochlor component exceeding 50% are designated as kosmochlor.
Compared with kosmochlor in jadeitite, the Cr-omphacite in this study has a relatively lower Cr2O3 content, ranging from 11.01 to 13.21 wt.% [6,25]. In contrast, the concentrations of CaO, MgO, and TFeO are significantly higher, with values of 4.99–5.93 wt%, 3.72–4.72 wt%, and 5.21–5.62 wt%, respectively. This composition is consistent with the Cr-omphacite cortex found in the outer rim of kosmochlor in previously studied amphibolites [8]. When plotted on the Quad-Jd-Aeg ternary classification diagram, the kosmochlor in this study falls within the omphacite field (Figure 8).
Kosmochlor (formerly known as ureyite) was initially identified as an accessory mineral in iron meteorites and carbonaceous chondrites [26,27,28]. Subsequently, terrestrial kosmochlors has been reported in the Myanmar Jade Belt [10,29], the western Sayan ophiolite of Russia [30], metamorphic rocks of the South Baikal region of Russia [23], the Mocchie and Susa areas of the Italian Alps [10], and the Renge and Kamuikotan metamorphic belts of Japan [31,32].
Cr-bearing pyroxenes, including kosmochlor and Cr-omphacite, are widely distributed in rocks from the Myanmar Jade Belt [9,10,29,33]. The most pure terrestrial kosmochlor (97 mol% NaCrSi2O6) has been identified as coronal growth surrounding chromite in the Myanmar jadeite jade [1]. Kosmochlor forms as a product of metasomatic reactions between chromite and jadeitizing fluids under high-pressure conditions [10,33]. Kosmochlor typically occurs as prismatic and fibrous euhedral crystals surrounding chromite in amphibolites or jadeitites, forming a corona texture [34]. In the Maw-sit-sit sample investigated by Colombo et al. (2000), kosmochlor occurring in the relict chromite rims was found to have a notably high degree of purity, with Cr2O3 content reaching 31.52 wt.% and Ca, Mg, and Fe concentrations below the detection limit of EPMA [6]. In the present study, however, complete replacement of chromite is observed, accompanied by a marked decrease in the Cr content of kosmochlor and significant increases in its Ca, Mg, and Fe contents, indicating that kosmochlor has transformed into Cr-omphacite (Table 3). Meanwhile, Cr-omphacite exists as discrete, fragmented grains embedded in an euhedral albite matrix. Cr-omphacite exhibits embayed grain boundaries and forms symplectic intergrowths with albite (Figure 5e,f, Figure 6a–c and Figure 7a,b). These textural characteristics constitute direct evidence of metasomatic replacement. While kosmochlor formation is attributed to a syn-metamorphic metasomatic process, progressive metasomatism in Maw-sit-sit jade drives isomorphous substitution of kosmochlor toward the diopside end-member (via Na+ + Cr3+ → Ca2+ + Mg2+ substitution), ultimately leading to the formation of Cr-omphacite.

5.2. Mineral Composition and Mineral Genesis Sequence

In this study, the main minerals identified in Maw-sit-sit jade are albite and Cr-omphacite, accompanied by minor amphibole (eckermannite and richterite), and occasional zircons. No jadeite or chromite were observed.
Zircons and chromites in jadeitite and related rocks from the Myanmar Jade Belt are regarded as protolith relics within the subduction channel-mantle wedge. In both kosmochlor-jadeitite and Maw-sit-sit rocks, chromite has been observed surrounded by kosmochlor (a metasomatic product of chromite) [9,10,29]. Typically, chromite occurs as black spots encircled by a bright green kosmochlor halo. Petrographic studies have confirmed that chromite, the source of chromium (Cr) imparting green coloration to jadeite, is derived from the protolithic peridotite [8,35]. The chromite composition and metasomatic characteristics observed in Maw-sit-sit rocks closely resemble those reported for chromite in green jadeitite [6]. Like replacement-type jadeitite (green jadeitite), Maw-sit-sit jade forms via the metasomatic replacement of chromite-bearing serpentinite. In Maw-sit-sit rocks, chromite and eckermannite are closely associated, often coexisting within a fine-grained matrix dominated by albite [6,7]. The absence of relict chromite in the Maw-sit-sit jade samples analyzed herein indicates that chromite underwent complete replacement.
In the Maw-sit-sit samples examined in this study, albite is the most abundant mineral, corresponding to the white portion observed in hand specimen. Albite exhibits an equigranular granoblastic texture with well-developed crystal forms and fills the interstices between Cr-omphacite and eckermannite. BSE images reveal that Cr-omphacite grains are relatively fine-grained, ranging in size from approximately 5 to 20 μm (Figure 6).
Eckermannite (Eck) is a relatively rare mineral but occurs in a significant proportion of our samples. It displays anhedral morphology, fiber bundles, and characteristic internal cleavage angles. Most naturally occurring or synthetic eckermannite samples reported to date are classified as either ferro-eckermannite or fluoro-eckermannite. The only formally documented eckermannite analysis was obtained from a specimen (AMNH H108401) in the mineral collection of the American Museum of Natural History. This sample is a jadeite-amphibolite from the Jade Belt in Kachin State, Myanmar, which was reviewed and approved by the IMA-CNMNC as a definitive eckermannite sample (Ballot 2013-136). It consists of a boundary layer of mixed white and emerald-green jadeite and black amphibole, with a distinct, sharp interface between the two. The associated minerals include jadeite and albite [36].
Occasionally, richterite (Rct) is present in the samples, typically exhibiting prismatic or acicular morphology with sizes ranging from 10 to over 100 μm. Compositional zoning in richterite is clearly distinguishable in BSE images. Richterite can form under diverse geological conditions, including contact metamorphic environments and mantle-derived xenoliths. Shi et al. (2003) identified richterite in the jadeitite from the Myanmar Jade Belt, where it occurs in amphibolites and kosmochlor-bearing rocks in association with jadeitite [37].
Petrographic evidence, such as the presence of Cr-omphacite and eckermannite fragments within albite (Figure 5, Figure 6 and Figure 7), suggests that Cr-omphacite and eckermannite crystallized before the albite. Eckermannite and Cr-omphacite represent the primary early-phase assemblage, as evidenced by their occurrence as enclosed grains and the presence of dissolution pores, which indicates they predate the fluid activity that caused their alteration. Their fragmented morphology and embayed grain boundaries, consistent with prior observations, further confirm that they were subjected to mechanical disruption and chemical dissolution during subsequent geological processes.
Albite occurs as euhedral crystals filling the interstices between Cr-omphacite and eckermannite (Figure 4). It also occurs as veinlets that cut through earlier Cr-omphacite and eckermannite (Figure 5e,f and Figure 6b). Additionally, albite commonly fills the cleavage planes of eckermannite, enclosing it as cleavage blocks. These findings confirm that albite is a late-stage mineral. Cr-omphacite, eckermannite, and albite form a disordered intergrowth, characterized by fine-grained crystals distributed randomly, collectively constituting an albite-Cr-omphacite-eckermannite (Ab+Cr-Omp+Eck) symplectite (Figure 7). The irregular, mutually interpenetrating grain boundaries give the samples a mottled texture under optical microscopy.
During the late stage of low-pressure retrograde metamorphism of plate exhumation, albite formed via Na-rich fluid-induced metasomatism and recrystallization. Ultimately, it combined with the two incompletely decomposed minerals, resulting in the formation of the Ab+Cr-Omp+Eck symplectite. This disordered Ab+Cr-Omp+Eck symplectic intergrowth confirms that the rock underwent a retrograde metamorphic process from high to low pressure. Richterite may be a product of recrystallization that formed during the same period as albite.
The mineralogical composition of Maw-sit-sit rocks in the Tawmaw area may vary depending on the specific sample. The mineralogical compositions of Samples X2 and X5 exhibit distinct variability, which further demonstrates the compositional heterogeneity of Maw-sit-sit. However, Maw-sit-sit rock can only resemble the aesthetic appearance of green jadeitite when its main minerals are albite and Cr-omphacite/kosmochlor (with little to no jadeite) and amphibole is present in minor amounts. Excessive mineral impurities, such as amphibole, can impart a mottled black appearance, rendering it overly “rocky” and unsuitable for use as jade material. Consequently, Maw-sit-sit jade is classified as Cr-omphacite-albitite or kosmochlor-albitite.

5.3. The Formation Process of Maw-Sit-Sit Jade

Maw-sit-sit jade (Cr-omphacite-albitite or kosmochlor-albitite) occurs in association with jadeitite in Myanmar and formed in a high-pressure/low-temperature (HP/LT) subduction zone environment. The most common albitites globally fall into two primary categories: those formed by hydrothermal metasomatism [38,39,40], and those crystallized directly from Na-rich magma [41]. However, Maw-sit-sit jade differs significantly from these two major albitite types in terms of its occurrence, mineral composition, and genesis.
Jadeitite is commonly found in serpentinite mélange, associated with high-pressure low-temperature (HP/LT) metamorphic rocks (e.g., eclogite and blueschist) [1,42,43]. It is widely accepted that green jadeitite originated through a metasomatic process, classified as R type [44,45,46,47,48,49]. The relict chromite in green jadeitite indicates that the peridotite protolith was infiltrated by Na-Al-Si-rich fluids from the subduction channel, with green jadeitite forming through metamorphic replacement [2,9,10]. In contrast, most jadeitites (predominantly white) are considered P-type, believed to have precipitated directly from Na-Al-Si-rich fluids within cavities or fractures of serpentinized peridotite or HP/LT metamorphic rocks [1,15,18,43,44,50,51,52]. These P-type jadeitites exhibit no evidence of protolith replacement structures. The jadeitite formation process terminated with a collisional tectonic event, with the serpentinite mélange rapidly exhumed along the subduction channel boundary, exposing jadeitite at the surface [15,53]. Jadeitite underwent accidental and rapid exhumation from depth, a process critical to preserving the HP-LT metamorphic rock assemblage [54].
The zircons hosted within the Maw-sit-sit samples display porous domains, embayed edges, and pseudomorphic textures, which are typical microstructural signatures of fluid modification (Figure 6c,d). Cr-omphacite grains exhibit substantial alteration along both grain boundaries and fractures. This evidence confirms that the fluid-induced formation of albite and fluid-driven modification played a significant role in the formation of the Maw-sit-sit jade. Albitite associated with jadeitite is primarily described in Myanmar, Guatemala, and Japan [10,18,55,56]. These albitites are genetically analogous to jadeitite in and closely associated with Na-Al-Si-rich fluids [55]. However, the origin of such fluids remains poorly understood at present.
In the Myanmar Jade Belt, Na-rich chemically active fluids persisted following jadeitite formation, as evidenced by the formation of over 10 Na-rich minerals at pressures lower than those required for jadeitite formation [1,57]. Without rapid exhumation, jadeitite would have reacted with surrounding fluids as pressure decreased, transforming into mineral assemblages stable under lower temperature-pressure conditions (e.g., albitite). For instance, jadeitite would have transformed into albitite. Previous studies on Myanmar albitite have identified late-stage Ba- and Sr-bearing minerals, which is consistent with the occurrence of these same minerals in jadeitite [1,57]. This indicates that the fluids involved in albitite formation were inherited from those responsible for jadeitite formation. Specifically, the albitite-forming fluids may derive from residual fluids remaining after jadeitite crystallization. Additionally, albite formation postdates that of Cr-omphacite, placing it at a later stage than the period of large-scale jadeitization. Previous studies indicate that the albitite associated with Myanmar jadeitite is low-temperature albite, with its formation temperature estimated to be below 300 °C [57]. Given the presence of water in the system and associated natrolite, the formation pressure of albitite is inferred to not exceeded 0.5 kb [57].
It can be inferred that Na-Al-Si-rich fluid metasomatizes the chromite-bearing protolith under high-pressure/low-temperature (HP/LT) conditions, forming jadeitite with amphiboles and high content of Cr-omphacite. During subsequent plate exhumation and decompression, jadeite underwent retrograde metamorphism under low-pressure/low-temperature (LP/LT) conditions with the involvement of residual Na-Al-Si fluids, resulting in the formation of albite (jadeite + Na+(aq) + Al3+(aq) + Si4+(aq) → albite). This process led to the replacement of early-formed minerals by euhedral albite, ultimately generating the Ab+Cr-Omp+Eck symplectic texture. Thus, Cr-omphacite- and amphibole-bearing jadeitite is transformed into Cr-omphacite- and amphibole-bearing albitite, known as Maw-sit-sit jade.

5.4. Identification of Maw-Sit-Sit Jade

Maw-sit-sit jade, with its high albite content, exhibits lower refractive index (RI: 1.55–1.56) and specific gravity (SG: 2.69–2.73) compared to kosmochlor-jadeitite (RI: 1.68–1.75; SG: 3.35–3.50) and jadeite jade (RI: 1.65–1.67; SG: 3.25–3.40) [25]. Additionally, Maw-sit-sit jade exhibits white or blue fluorescence in punctate or banded forms under ultraviolet (UV) light. This characteristic fluorescence response is attributed to its albite content. In contrast, both kosmochlor-jadeitite and jadeite jade remain inert under UV illumination. This fluorescence difference aids in distinguishing Maw-sit-sit jade from kosmochlor-jadeitite and jadeite jade.

6. Conclusions

High-quality Maw-sit-sit jade from Myanmar Jade Belt is a Cr-omphacite-albitite, primarily composed of albite and Cr-omphacite, with minor amphibole (eckermannite and richterite). Jadeite and relict chromite are absent in the studied samples. Maw-sit-sit jade exhibits a relatively wide range of refractive index (RI: 1.5–1.6) and specific gravity (SG: 2.5–3.0), both of which are lower than those of kosmochlor-jadeitite and jadeite. Additionally, the difference in fluorescence when exposed to UV lamps aids in distinguishing between Maw-sit-sit jade (which exhibits punctate or banded fluorescence) and kosmochlor-jadeitite and jadeite jade (both of which are inert).
Albite occurs with euhedral habits, filling the interstices between early-formed Cr-omphacite and eckermannite, which is textural evidence of its late-stage origin. Eckermannite and Cr-omphacite occur as enclosed grains with embayed boundaries and dissolution pores, indicating they experienced mechanical disruption and chemical dissolution during subsequent geological processes. Petrogenetically, Maw-sit-sit jade forms via a two-stage process: (1) Under high-pressure/low-temperature (HP/LT) conditions in the subduction zone, Na-Al-Si-rich fluids metasomatize chromite-bearing serpentinite protoliths, generating an early assemblage of jadeite, Cr-omphacite and amphiboles, and (2) during subsequent plate exhumation and decompression, jadeite underwent retrograde metamorphism under low-pressure/low-temperature (LP/LT) conditions involving residual Na-Al-Si fluids, resulting in the formation of albite. This process led to the replacement of early-formed minerals by euhedral albite, ultimately generating the Ab+Cr-Omp+Eck symplectic texture. Thus, jadeitite containing Cr-omphacite and amphibole transforms into albitite containing Cr-omphacite and amphibole, known as Maw-sit-sit jade. This study clarifies the genesis of Maw-sit-sit jade and advances the understanding of fluid-related processes in subduction zones.

Author Contributions

Conceptualization, Y.Z. and G.S.; methodology, Y.Z.; software, J.W.; validation, Y.Z. and J.W.; formal analysis, Y.Z.; investigation, Y.Z. and J.W.; resources, Y.Z. and G.S.; data curation, Y.Z. and J.W.; writing—original draft preparation, Y.Z.; writing—review and editing, Y.Z. and G.S.; visualization, Y.Z.; supervision, G.S.; project administration, G.S.; funding acquisition, G.S. All authors have read and agreed to the published version of the manuscript.

Funding

This investigation was supported by the National Natural Science Foundation of China (grant number 42273044) and 2025 Teaching Reform—Research and Application of Teaching Laboratory and Experimental Technology at China University of Geosciences (Beijing) (No. 640125002, Project SYJS202504).

Data Availability Statement

The data presented in this study are available within the article.

Acknowledgments

The authors acknowledge the support of the Laboratory of the School of Gemology, China University of Geosciences (Beijing).

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Shi, G.; Harlow, G.E.; Wang, J.; Wang, J.; Enoch, N.G.; Wang, X.; Cao, S.M.; Enyuancui, W. Mineralogy of jadeitite and related rocks from Myanmar: A review with new data. Eur. J. Mineral. 2012, 24, 345–370. [Google Scholar] [CrossRef]
  2. Searle, M.P.; Palin, R.M.; Gardiner, N.J.; Htun, K.; Wade, J. The Burmese Jade Mines belt: Origins of jadeitites, serpentinites, and ophiolitic peridotites and gabbros. J. Geol. Soc. 2023, 180, jgs2023-004. [Google Scholar] [CrossRef]
  3. Zhang, Y.; Shi, G. Origin of Blue-Water Jadeite Jades from Myanmar and Guatemala: Differentiation by Non-Destructive Spectroscopic Techniques. Crystals 2022, 12, 1448. [Google Scholar] [CrossRef]
  4. Gübelin, E. Maw-sit-sit—A new decorative gemstone from Burma. J. Gemmol. 1965, 9, 329–344. [Google Scholar] [CrossRef]
  5. Hänni, H.A.; Meyer, J. Maw-sit-sit (kosmochlor jade): A metamorphic rock with a complex composition from Myanmar (Burma). In Proceedings of the 26th International Gemmological Conference, Idar-Oberstein, Germany, 27 September–3 October 1998; pp. 22–24. [Google Scholar]
  6. Colombo, F.; Rinaudo, C.; Trossarelli, C. The mineralogical composition of maw-sit-sit from Myanmar. J. Gemmol. 2000, 27, 87–92. [Google Scholar] [CrossRef]
  7. Nyunt, T.T. Petrological and Geochemical Contribution to the Origin of Jadeitite and Associated Rocks of the Tawmaw Area, Kachin State, Myanmar. Ph.D. Thesis, University of Stuttgart, Stuttgart, Germany, 2009. [Google Scholar]
  8. Zhang, Y.; Shi, G.; Wen, J. Chromite and Its Thin Kosmochlor and Cr-Omphacite Cortex in Amphibolite from the Myanmar Jadeite Deposits. Crystals 2025, 15, 79. [Google Scholar] [CrossRef]
  9. Mével, C.; Kienast, J.-R. Jadeite-kosmochlor solid solution and chromian sodic amphiboles in jadeitites and associated rocks from Tawmaw (Burma). Bull. Minéral. 1986, 109, 617–633. [Google Scholar] [CrossRef]
  10. Harlow, G.E.; Olds, E.P. Observations on terrestrial ureyite and ureyitic pyroxene. Am. Mineral. 1987, 72, 126–136. [Google Scholar] [CrossRef]
  11. Hughes, R.W.; Galibert, O.; Bosshart, G.; Ward, F.; Oo, T.; Smith, M.; Sun, T.T.; Harlow, G.E. Burmese jade: The inscrutable gemstone. Gems. Gemol. 2000, 36, 2–26. [Google Scholar] [CrossRef]
  12. Mitchell, A.; Htay, M.T.; Htun, K.M. Middle Jurassic arc reversal, Victoria–Katha Block and Sibumasu Terrane collision, jadeite formation and Western Tin Belt generation, Myanmar. Geol. Mag. 2021, 158, 1487–1503. [Google Scholar] [CrossRef]
  13. Mitchell, A. Jade Mines–Loimaw Uplift. In Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar; Elsevier: Amsterdam, The Netherlands, 2018; pp. 439–460. [Google Scholar] [CrossRef]
  14. Morley, C.K.; Naing, T.T.; Searle, M.; Robinson, S.A. Structural and tectonic development of the Indo-Burma ranges. Earth-Sci. Rev. 2020, 200, 102992. [Google Scholar] [CrossRef]
  15. Harlow, G.E.; Tsujimori, T.; Sorensen, S.S. Jadeitites and Plate Tectonics. Annu. Rev. Earth Planet. Sci. 2015, 43, 105–138. [Google Scholar] [CrossRef]
  16. Gem-A, The Gemmological Association of Great Britain. The Diploma in Gemmology Course. Gem-A, The Gemmological Association of Great Britain: London, UK, 2009; pp. 4–15. [Google Scholar]
  17. Warr, L.N. IMA–CNMNC approved mineral symbols. Miner. Mag. 2021, 85, 291–320. [Google Scholar] [CrossRef]
  18. Johnson, C.A.; Harlow, G.E. Guatemala jadeitites and albitites were formed by deuterium-rich serpentinizing fluids deep within a subduction zone. Geology 1999, 27, 629–632. [Google Scholar] [CrossRef]
  19. Harlow, G.; Sisson, V.; Sorensen, S. Jadeitite from Guatemala: New observations and distinctions among multiple occurrences. Geol. Acta 2011, 9, 363–387. [Google Scholar] [CrossRef]
  20. Harlow, G.E.; Quinn, E.P.; Rossman, G.R.; Rohtert, W.R. Blue omphacite from Guatemala. Gems. Gemol. 2004, 40, 68–70. [Google Scholar]
  21. Skelton, R.; Walker, A.M. The effect of cation order on the elasticity of omphacite from atomistic calculations. Phys. Chem. Miner. 2015, 42, 677–691. [Google Scholar] [CrossRef]
  22. Flores, K.E.; Martens, U.C.; Harlow, G.E.; Brueckner, H.K.; Pearson, N.J. Jadeitite formed during subduction: In situ zircon geochronology constraints from two different tectonic events within the Guatemala Suture Zone. Earth Planet. Sci. Lett. 2013, 371–372, 67–81. [Google Scholar] [CrossRef]
  23. Reznitsky, L.Z.; Sklyarov, E.V.; Galuskin, E.V. Complete isomorphic join diopside–kosmochlor CaMgSi2O6–NaCrSi2O6 in metamorphic rocks of the Sludyanka complex (southern Baikal region). Russ. Geol. Geophys. 2011, 52, 40–51. [Google Scholar] [CrossRef]
  24. Morimoto, N. Nomenclature of Pyroxenes. Miner. Pet. 1988, 39, 55–76. [Google Scholar] [CrossRef]
  25. Franz, L.; Sun, T.T.; Hanni, H.A. A Comparative Study of Jadeite, Omphacite and Kosmochlor Jades from Myanmar, and Suggestions for a Practical Nomenclature. J. Gemmol. 2014, 34, 210–229. [Google Scholar] [CrossRef]
  26. Frondel, C.; Klein, C. Ureyite, NaCrSi2O6: A New Meteoritic Pyroxene. Science 1965, 149, 742–744. [Google Scholar] [CrossRef]
  27. Couper, A.G.; Hey, M.H.; Hutchison, R. Cosmochlore—A new examination. Miner. Mag. 1981, 44, 265–267. [Google Scholar] [CrossRef]
  28. Greshake, A.; Bischoff, A. Chromium-bearing Phases in Orgueil (CI): Discovery of Magnesiochromite (MgCr2O4), Ureyite (NaCrSi2O6), and ChromiumOxide (Cr2O3). Lunar Planet. Sci. 1996, 27, 461–462. [Google Scholar]
  29. Ouyang, C.M. A terrestrial source of ureyite. Am. Mineral. 1984, 69, 1180–1183. [Google Scholar] [CrossRef]
  30. Dobretsov, N.L.; Tatarinov, A.V. Jadeite and Nephrite in Ophiolite from West Sayan; Nauka Press: Novosibirsk, Russia, 1983; p. 125. [Google Scholar]
  31. Sakamoto, S.; Takasu, A. Kosmochlor from the Osayama ultramafic body in the Sangun metamorphic belt, southewest Japan. J. Geol. Soc. Jpn. 1996, 102, 49–52. [Google Scholar] [CrossRef]
  32. Akira, T.; Yasumitsu, S.; Yoshiya, O.; Takahiko, O.; Shizue, S. Newly identified end-member kosmochlor from the Yamanobo outcrop of the Renge metamorphic belt, Itoigawa, central Japan. Earth Sci. J. 2022, 76, 37–42. [Google Scholar] [CrossRef]
  33. Ouyang, C.M.; Qi, L.J. Hte long sein—A new variety of chrome jadeite jade. J. Gemmol. 2001, 27, 321–327. [Google Scholar] [CrossRef]
  34. Xing, Y.; Qi, L. Compositional zoning and evolution of symplectite coronas in jadeitite. Mater. Test. 2024, 66, 1207–1218. [Google Scholar] [CrossRef]
  35. Zhang, Y.; Shi, G.; Wen, J. Manganese-Rich Chromite in Myanmar Jadeite Jade: A Critical Source of Chromium and Manganese and Its Role in Coloration. Crystals 2025, 15, 704. [Google Scholar] [CrossRef]
  36. Oberti, R.; Boiocchi, M.; Hawthorne, F.C.; Ball, N.A.; Harlow, G.E. Eckermannite revised: The new holotype from the Jade Mine Tract, Myanmar—Crystal structure, mineral data, and hints on the reasons for the rarity of eckermannite. Am. Mineral. 2015, 100, 909–914. [Google Scholar] [CrossRef]
  37. Shi, G.-H.; Cui, W.-Y.; Tropper, P.; Wang, C.-Q.; Shu, G.-M.; Yu, H. The petrology of a complex sodic and sodic?calcic amphibole association and its implications for the metasomatic processes in the jadeitite area in northwestern Myanmar, formerly Burma. Contrib. Miner. Pet. 2003, 145, 355–376. [Google Scholar] [CrossRef]
  38. Cathelineau, M. Accessory mineral alteration in peraluminous granites at the hydrothermal stage: A review. Rend. Soc. Ital. Mineral. Petrol 1988, 43, 499–508. [Google Scholar]
  39. Yang, L.; Deng, J.; Guo, C.; Zhang, J.; Jiang, S.; Gao, B.; Gong, Q.; Wang, Q. Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China. Resour. Geol. 2009, 59, 181–193. [Google Scholar] [CrossRef]
  40. Sun, X.; Deng, J.; Zhao, Z.; Zhao, Z.; Wang, Q.; Yang, L.; Gong, Q.; Wang, C. Geochronology, petrogenesis and tectonic implications of granites from the Fuxin area, Western Liaoning, NE China. Gondwana Res. 2010, 17, 642–652. [Google Scholar] [CrossRef]
  41. Schwartz, M.O. Geochemical criteria for distinguishing magmatic and metasomatic albite-enrichment in granitoids—Examples from the tantalum-lithium granite Yichun (China) and the tin-tungsten deposit Tikus (Indonesia). Miner. Deposita 1992, 27, 101–108. [Google Scholar] [CrossRef]
  42. Harlow, G.E.; Flores, K.E.; Marschall, H.R. Fluid-mediated mass transfer from a paleosubduction channel to its mantle wedge: Evidence from jadeitite and related rocks from the Guatemala Suture Zone. Lithos 2016, 258–259, 15–36. [Google Scholar] [CrossRef]
  43. Angiboust, S.; Glodny, J.; Cambeses, A.; Raimondo, T.; Monié, P.; Popov, M.; Garcia-Casco, A. Drainage of subduction interface fluids into the forearc mantle evidenced by a pristine jadeitite network (Polar Urals). J. Metamorph. Geol. 2020, 39, 473–500. [Google Scholar] [CrossRef]
  44. Chen, Y.; Huang, F.; Shi, G.-H.; Wu, F.-Y.; Chen, X.; Jin, Q.-Z.; Su, B.; Guo, S.; Sein, K.; Nyunt, T.T. Magnesium Isotope Composition of Subduction Zone Fluids as Constrained by Jadeitites From Myanmar. J. Geophys. Res. Solid Earth 2018, 123, 7566–7585. [Google Scholar] [CrossRef]
  45. Shigeno, M.; Mori, Y.; Nishiyama, T. Reaction microtextures in jadeitites from the Nishisonogi metamorphic rocks, Kyushu, Japan. J. Mineral. Petrol. Sci. 2007, 100, 237–246. [Google Scholar] [CrossRef]
  46. Compagnoni, R.; Rolfo, F.; Castelli, D. Jadeitite from the Monviso meta-ophiolite, western Alps: Occurrence and genesis. Eur. J. Mineral. 2012, 24, 333–343. [Google Scholar] [CrossRef]
  47. Mori, Y.; Orihashi, Y.; Miyamoto, T.; Shimada, K.; Shigeno, M.; Nishiyama, T. Origin of zircon in jadeitite from the Nishisonogi metamorphic rocks, Kyushu, Japan. J. Metamorph. Geol. 2011, 29, 673–684. [Google Scholar] [CrossRef]
  48. Tsujimori, T.; Harlow, G.E. Petrogenetic relationships between jadeitite and associated high-pressure and low-temperature metamorphic rocks in worldwide jadeitite localities: A review. Eur. J. Mineral. 2012, 24, 371–390. [Google Scholar] [CrossRef]
  49. Chen, A.-X.; Chen, X.; Chen, Y.; Han, X.-Q.; Wang, Y.-J.; Huang, F. Low-δ56Fe fluid released from serpentinite as recorded by iron isotopes of Myanmar jadeitites. Chem. Geol. 2023, 639, 121730. [Google Scholar] [CrossRef]
  50. Sorensen, S.S.; Harlow, G.E.; Rumble, D.I. The origin of jadeitite-forming subduction-zone fluids: CL-guided SIMS oxygen-isotope and trace-element evidence. Am. Mineral. 2006, 91, 979–996. [Google Scholar] [CrossRef]
  51. Kawamoto, T.; Hertwig, A.; Schertl, H.-P.; Maresch, W.V. Fluid inclusions in jadeitite and jadeite-rich rock from serpentinite mélanges in northern Hispaniola: Trapped ambient fluids in a cold subduction channel. Lithos 2018, 308–309, 227–241. [Google Scholar] [CrossRef]
  52. Minnaert, C.; Angiboust, S.; Herviou, C.; Melis, R.; Glodny, J.; Cambeses, A.; Raimondo, T.; Payne, J.; Rigaudier, T.; Cárdenas-Párraga, J.; et al. Tracking fluid sources in mantle wedge jadeitites: Petro-geochemical constraints and implications for fluid venting above the subduction interface. Chem. Geol. 2025, 695, 123046. [Google Scholar] [CrossRef]
  53. Chen, A.-X.; Li, Y.-H.; Chen, Y.; Yu, H.-M.; Huang, F. Silicon isotope composition of subduction zone fluids as recorded by jadeitites from Myanmar. Contrib. Miner. Pet. 2019, 175, 6. [Google Scholar] [CrossRef]
  54. Shi, G.; Lei, W.; He, H.; Ng, Y.N.; Liu, Y.; Liu, Y.; Yuan, Y.; Kang, Z.; Xie, G. Superimposed tectono-metamorphic episodes of Jurassic and Eocene age in the jadeite uplift, Myanmar, as revealed by 40Ar/39Ar dating. Gondwana Res. 2014, 26, 464–474. [Google Scholar] [CrossRef]
  55. Harlow, G.E. Jadeitites, albitites and related rocks from the Motagua Fault Zone, Guatemala. J. Metamorph. Geol. 1994, 12, 49–68. [Google Scholar] [CrossRef]
  56. Hirajima, T. Jadeite and jadeitite-bearing rock in the Sanbagawa and the Kamuikotan belts, Japan: A review(Review). J. Mineral. Petrol. Sci. 2017, 112, 237–246. [Google Scholar] [CrossRef]
  57. Wang, J.; Shi, G.; Wang, J.; Yuan, Y.; Yang, M. Hydrothermal albitite from the Myanmar jadeite deposit. Acta Petrol. Sin. 2013, 29, 1450–1460. [Google Scholar]
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Figure 1. Geological sketch maps of the Myanmar jadeite belt (modified after Zhang et al., 2025) [8].
Figure 1. Geological sketch maps of the Myanmar jadeite belt (modified after Zhang et al., 2025) [8].
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Figure 2. Photos of Maw-sit-sit jade samples from Myanmar Jade Belt.
Figure 2. Photos of Maw-sit-sit jade samples from Myanmar Jade Belt.
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Figure 3. Microscopic external characteristics of the samples: (a) Maw-sit-sit jade consists of albite (white), Cr-omphacite (bright green), and minor amphibole (dark green). (b) Cr-omphacite exhibits bright green with varying saturation. (c) The distinctive interlocking texture between Cr-omphacite and albite. (d) The distinctive “undercutting” effect on the polished surface observed under a gemological microscope (arrowed). Ab: albite and Cr-Omp: Cr-omphacite [17].
Figure 3. Microscopic external characteristics of the samples: (a) Maw-sit-sit jade consists of albite (white), Cr-omphacite (bright green), and minor amphibole (dark green). (b) Cr-omphacite exhibits bright green with varying saturation. (c) The distinctive interlocking texture between Cr-omphacite and albite. (d) The distinctive “undercutting” effect on the polished surface observed under a gemological microscope (arrowed). Ab: albite and Cr-Omp: Cr-omphacite [17].
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Figure 4. The microphotograph of albite in the sample displays equigranular granoblastic texture under cross-polarized light (Ab: albite and Cr-Omp: Cr-omphacite [17]).
Figure 4. The microphotograph of albite in the sample displays equigranular granoblastic texture under cross-polarized light (Ab: albite and Cr-Omp: Cr-omphacite [17]).
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Figure 5. Photomicrographs of textural and mineralogical characteristics of selected samples. Photos (a,c,e) are in plane-polarized light, and (b,d,f) are in cross-polarized light. Rct: richterite, Eck: eckermannite, Ab: albite and Cr-Omp: Cr-omphacite [17].
Figure 5. Photomicrographs of textural and mineralogical characteristics of selected samples. Photos (a,c,e) are in plane-polarized light, and (b,d,f) are in cross-polarized light. Rct: richterite, Eck: eckermannite, Ab: albite and Cr-Omp: Cr-omphacite [17].
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Figure 6. BSE images of Cr-omphacite-albite symplectic texture and zircon in Maw-sit-sit jade (Ab: albite; Cr-Omp: Cr-omphacite; Zrn: zircon; Rct: richterite [17]). (a): Cr-omphacite exhibits embayed grain boundaries and forms symplectic intergrowth with albite. (b): Albite occurs as veinlets that cut through earlier Cr-omphacite and eckermannite. (c,d): Zircons are severely altered with their original crystal structure being partially replaced and richterite grains exhibit oscillatory zoning patterns.
Figure 6. BSE images of Cr-omphacite-albite symplectic texture and zircon in Maw-sit-sit jade (Ab: albite; Cr-Omp: Cr-omphacite; Zrn: zircon; Rct: richterite [17]). (a): Cr-omphacite exhibits embayed grain boundaries and forms symplectic intergrowth with albite. (b): Albite occurs as veinlets that cut through earlier Cr-omphacite and eckermannite. (c,d): Zircons are severely altered with their original crystal structure being partially replaced and richterite grains exhibit oscillatory zoning patterns.
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Figure 7. Reflected light photomicrographs of the albite-Cr-omphacite-eckermannite symplectic texture (Ab: albite; Cr-Omp: Cr-omphacite; Eck: eckermannite [17]). (a): Cr-omphacite exhibits embayed grain boundaries. (b): Cr-omphacite forms symplectic intergrowths with albite and eckermannite. (c): Richterite grain exhibit oscillatory zoning pattern. (d): Albite fills the cleavage planes of eckermannite, enclosing it as cleavage blocks.
Figure 7. Reflected light photomicrographs of the albite-Cr-omphacite-eckermannite symplectic texture (Ab: albite; Cr-Omp: Cr-omphacite; Eck: eckermannite [17]). (a): Cr-omphacite exhibits embayed grain boundaries. (b): Cr-omphacite forms symplectic intergrowths with albite and eckermannite. (c): Richterite grain exhibit oscillatory zoning pattern. (d): Albite fills the cleavage planes of eckermannite, enclosing it as cleavage blocks.
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Figure 8. The Cr-omphacite components of this study are plotted in the region of omphacite on a ternary Quad-Jd-Aeg classification diagram (base map from Morimoto, 1988 [24]). Quad: quadrilateral pyroxene, i.e., WEF: wollastonite (Wo, Ca2Si2O6) + enstatite (En, Mg2Si2O6) + ferrosilite (Fs, Fe2Si2O6).
Figure 8. The Cr-omphacite components of this study are plotted in the region of omphacite on a ternary Quad-Jd-Aeg classification diagram (base map from Morimoto, 1988 [24]). Quad: quadrilateral pyroxene, i.e., WEF: wollastonite (Wo, Ca2Si2O6) + enstatite (En, Mg2Si2O6) + ferrosilite (Fs, Fe2Si2O6).
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Table 1. Sample descriptions and gemological characteristics.
Table 1. Sample descriptions and gemological characteristics.
SampleColorShapeSpecific GravityRIUV FluorescenceDescriptions
X2Bright green, partly whitepartly white and black.Drop-shaped cabochon2.731.56SW: medium blue-white.
LW: Weak.		The green Cr-omphacite is dominant, with a small amount of white albite and black-green amphibole.
X5Bright green, partly white.Rectangular cabochon2.691.55SW: medium blue-white.
LW: Weak.		The white albite and green Cr-omphacite are dominant, with a small amount of black-green amphibole.
SW: short-wavelength ultraviolet (253.7 nm); LW: long-wavelength ultraviolet (365 nm).
Table 2. The chemical composition and atomic formula of albites in sample X2.
Table 2. The chemical composition and atomic formula of albites in sample X2.
SamplesX2-40X2-41X2-46X2-51X2-52
SiO268.8969.0768.6468.7268.93
TiO2ndnd0.110.05nd
Al2O318.9318.6416.7918.8419.3
Cr2O3nd0.221.370.530.04
FeOtot0.010.080.460.250.06
NiOnd0.040.030.020.03
MgOnd0.030.40.110.02
MnO0.02ndnd0.02nd
CaOnd0.050.590.160.01
BaO0.04nd0.04nd0.01
Na2O11.511.1310.9911.3811.43
K2O0.030.240.020.020.02
Total99.4399.599.43100.1199.84
Si3.02 3.03 3.05 3.01 3.02
Al0.98 0.96 0.88 0.97 1.00
Crnd0.01 0.04 0.01 nd
Mgndnd0.03 0.01 nd
Fe3+ndnd0.02 0.01 nd
Candnd0.03 0.01 nd
Na0.98 0.95 0.95 0.97 0.97
Knd0.01 ndndnd
Sum4.98 4.97 4.99 5.00 5.00
Note: nd = not detected. FeOtot = total iron. Spots X2-46 and X2-51 contain minor Cr-omphacite inclusions, leading to detectable Cr.
Table 3. The chemical composition and atomic formula of Cr-omphacites in sample X2.
Table 3. The chemical composition and atomic formula of Cr-omphacites in sample X2.
SamplesX2-43X2-50
SiO255.3755.85
TiO21.191.23
Al2O34.575.07
Cr2O313.2111.01
FeOtot5.215.62
NiOnd0.01
MgO3.724.72
MnO0.060.02
CaO4.995.93
Na2O11.2010.63
K2Ond0.01
Total99.51100.10
Si2.032.03
Ti0.030.03
Al0.200.22
Cr0.380.32
Fe3+0.090.09
Mg0.200.26
Fe2+0.070.08
Ca0.200.23
Na0.800.75
Sum4.004.00
Jd15.0519.22
WEF22.8927.37
Kos38.3031.60
Aeg23.7621.81
Note: nd = not detected. FeOtot = total iron. WEF: wollastonite (Wo, Ca2Si2O6) + enstatite (En, Mg2Si2O6) + ferrosilite (Fs, Fe2Si2O6), Jd: jadeite, Kos: kosmochlor and Aeg: aegirine.
Table 4. The chemical composition and atomic formula of amphiboles in sample X2.
Table 4. The chemical composition and atomic formula of amphiboles in sample X2.
SamplesX2-42X2-44X2-47X2-48
EckRctRctRct
SiO261.0759.7759.9459.46
TiO20.060.140.090.20
Al2O38.791.431.310.97
Cr2O33.574.152.914.77
FeOtot2.093.564.143.55
NiO0.070.070.070.07
MgO10.4917.0018.3417.00
MnO0.020.060.090.09
CaO0.401.931.932.03
Na2O10.289.329.459.38
K2O0.190.240.150.26
Total97.0497.6698.4197.79
Si8.008.008.008.00
Sum T8.008.008.008.00
Al1.400.230.210.16
Si0.260.240.20.31
Ti0.010.010.010.02
Cr0.380.450.320.52
Fe2+0.240.410.470.41
Mnnd0.010.010.01
Mg2.113.493.743.5
Ni0.010.010.010.01
Sum C4.414.854.974.94
Ca0.060.280.280.30
Na1.941.721.721.70
Sum B2.002.002.002.00
Na0.750.780.790.81
K0.030.040.030.05
Sum A0.790.820.820.86
Mg/(Mg + Fe2+)0.900.890.890.90
Note: nd = not detected. FeOtot = total iron. Eck: eckermannite and Rct: richterite.
Table 5. Quantitative X-ray Energy Dispersive Spectroscopy (EDS) Results of Zircon.
Table 5. Quantitative X-ray Energy Dispersive Spectroscopy (EDS) Results of Zircon.
SampleX2-45X2-53
SiO230.1330.95
ZrO269.8769.05
Total100.00100.00
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Zhang, Y.; Shi, G.; Wen, J. Mineralogical, Gemological Characteristics and Petrogenesis of High-Quality Maw-Sit-Sit Jade from the Myanmar Jade Belt. Crystals 2025, 15, 983. https://doi.org/10.3390/cryst15110983

AMA Style

Zhang Y, Shi G, Wen J. Mineralogical, Gemological Characteristics and Petrogenesis of High-Quality Maw-Sit-Sit Jade from the Myanmar Jade Belt. Crystals. 2025; 15(11):983. https://doi.org/10.3390/cryst15110983

Chicago/Turabian Style

Zhang, Yu, Guanghai Shi, and Jiabao Wen. 2025. "Mineralogical, Gemological Characteristics and Petrogenesis of High-Quality Maw-Sit-Sit Jade from the Myanmar Jade Belt" Crystals 15, no. 11: 983. https://doi.org/10.3390/cryst15110983

APA Style

Zhang, Y., Shi, G., & Wen, J. (2025). Mineralogical, Gemological Characteristics and Petrogenesis of High-Quality Maw-Sit-Sit Jade from the Myanmar Jade Belt. Crystals, 15(11), 983. https://doi.org/10.3390/cryst15110983

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