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Green nephrites are widely pursued for their mild texture and vivid color. In recent years, many Russian green nephrites appeared in China (the world’s largest nephrite market) and competed with the Chinese Manas green nephrites, which are traditionally highly valued. In this study, we compared the appearance, mineralogy and geochemical features (w...
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The Hirvilavanmaa (Au-only) and Naakenavaara (Cu-Co-Au-Ni) deposits, located only 5 km apart in the Paleoproterozoic Central Lapland belt (CLB) in northern Finland, represent two types of orogenic gold mineralization that dominate the CLB: (1) Au-only and (2) Au with atypical metal association, respectively. In this study, we compare these deposits...
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... Garnet of a grossular-uvarovite composition was found in the nephrite of the Nasławice deposit in Poland [28], the Bazhenov chrysotile-asbestos deposit [35] and the Pounamu Ultramafics, Westland, New Zealand [30]. So far, the only reliable finding of abundant low-alumina uvarovite in S-type nephrite has been recorded at the Manas deposit in the Northern Tien Shan in the north of the Xinjiang Uygur Autonomous Region of China [7]. A single uvarovite analysis is also reported from the nearby Puserka jadeite deposit, related to the Syum-Key ultramafic massif [51]. ...
... A positive Eu anomaly is observed at the Manas deposit, and a negative one at the Eastern Sayan deposits, with a right slope [7]. A positive Eu anomaly indicates a complex source of ore-forming fluid [7]. ...
... Based on the peculiarities of the distribution of REE in the Nyrdvomenshor nephrite, it can be assumed that it was formed under the influence of a complex, non-acidic solution in an oxidizing environment. A positive Eu anomaly is observed at the Manas deposit, and a negative one at the Eastern Sayan deposits, with a right slope [7]. A positive Eu anomaly indicates a complex source of ore-forming fluid [7]. ...
We studied the quality characteristics, chemical, mineral and isotope composition of nephrite, diopsidite and rodingite of the Nyrdvomenshor nephrite deposit in the Polar Urals. We applied visual petrographic and mineralogical studies, X-ray spectral fluorescence, ICP-MS analysis, and a scanning electron microscope with a dispersive microanalysis system, to measure the oxygen isotope composition. According to its quality characteristics, the nephrite was substandard. Here, uvarovite, which forms idiomorphic grains, sometimes sheath-like and less often xenomorphic elongated, and substituting the chromite, was commonly encountered. The nephrite was formed due to both metamorphic and metasomatic processes. The serpentinite was replaced by diopsidite, which was then replaced by nephrite. The metamorphism intensified the metasomatism of the serpentinite melange and provided the cryptocrystalline tangled-fibrous structure of the nephrite. Then, metamorphism and metasomatism led to the formation of omphacite and the cracking of the nephrite, which reduced its quality. As these processes progressed, the contribution of the crustal fluid increased.
... Garnet of the grossular-uvarovite composition was found in the nephrite of the Nasławice deposit in Poland [26] and the Bazhenov chrysotile-asbestos deposit [36]. So far, the only reliable finding of abundant low-alumina uvarovite in S-type nephrite has been recorded at the Manas deposit in the Northern Tien Shan in the north of the Xinjiang Uygur Autonomous Region of China [7]. ...
... 3), the distribution pattern is flat with a weak right slope -enrichment with light REE, positive Eu anomaly (Fig. 8). A positive Eu anomaly is observed at the Manas field, and a negative one -at the Eastern Sayan deposits with a right slope [7]. A positive Eu anomaly indicates a complex source of ore-forming fluid [7]. ...
... A positive Eu anomaly is observed at the Manas field, and a negative one -at the Eastern Sayan deposits with a right slope [7]. A positive Eu anomaly indicates a complex source of ore-forming fluid [7]. The Kutcho deposit has a left slope -enrichment with heavy REE, which is explained by the acidic environment of nephrite formation, and the weakly negative Eu anomaly is attributed to the reducing metallogenic environment [22]. ...
We have studied quality characteristics, chemical, mineral and isotope composition of nephrite, diopsidite and rodingite of the Nyrdvomenshor deposit in the Polar Urals. We applied the visual petrographic and mineralogical studies, X-ray spectral fluorescence, ICP-MS analysis, scanning electron microscope with the dispersive microanalysis system, oxygen isotope composition was measured. According to its quality characteristics, the nephrite is substandard. Here, uvarovite, which forms idiomorphic grains, sometimes sheath-like, less often xenomorphic elongated, and substituting chromite are commonly encountered. The nephrite was formed due to both metamorphic and metasomatic processes. Serpentinite was replaced by diopsidite, which was then replaced by nephrite. Metamorphism intensified metasomatism of the serpentinite melange and provided a cryptocrystalline tangled-fibrous structure of the nephrite. Then metamorphism and metasomatism led to the formation of omphacite and cracking of the nephrite, which reduced its quality. As these processes progressed, contribution of crustal fluid increased.
... Studies of the textures and mineral components of weathered cortexes have gemological applications in terms of identifying and grading raw jadeite and in the design and manufacture of jade pieces from Myanmar. Moreover, such studies can improve our understanding of the changes in jadeite jade caused by weathering from other localities, such as Guatemala (e.g., Xing et al. [19]), and of the changes in other rough jade pieces due to weathering, such as nephrites from China and Russia (e.g., Jiang et al. [20], Wang and Shi [21]), as well as the differences from the weathering of multiple-mineral rocks. ...
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.
... Finally, another approach to colour characterization is to use it as an additional proxy along with other types of data. In the paper by Wang and Shi [5], macroscopic colour evaluation using the Munsell colour theory was correlated to chemical and mineralogical characterization to distinguish green nephrites (amphibole-based jade) from the Manas County (China) and Eastern Sayan (Russia). In the paper by Díaz-Acha et al. [6], colourimetric measurements of archaeological and geological samples of gemmy phosphates (variscite and turquoise) from the Neolithic mines of Gavà (Spain) supplemented other characterization proxies, a correlation between Cr 3+ and gemmy variscite was suggested and the chromatic effect of intimate natural mixtures with other minerals was also established. ...
Colour is one of the most eye-catching properties of some minerals and rocks [...]
Research subject. Nephrite and related rocks from the Nyrdvomenshor deposit in the Polar Urals were studied. The Nyrdvomenshor deposit is located in the exocontact of the Rai-Iz ultramafic massif, confined to the Main Ural Fault. The deposit was developed in the process of geological exploration; a license has been issued for a part of the deposit.
Aim. To study the nephrite and related rocks from alluvial of the deposit, to formulate a model of its origin.
Methods. Qualitative characteristics were assessed visually using a binocular microscope and a special flashlight. The chemical composition was determined by the X-ray fluorescence method. The contents of trace elements were determined by ICP-MS analysis. The mineral composition was studied on a scanning electron microscope with an energy dispersive microanalysis system. Measurements of the isotopic composition of oxygen were carried out.
Results. In addition to vesuvianite rodingite, hydrogarnet rodingite was found to be common at the deposit. The studied nephrite is substandard. Tremolite predominates in nephrite, diopside forms relic grains. Uvarovite is widespread, forming both idiomorphic grains, sometimes sheath, less often elongated xenomorphic, and replacing chromite. Omphacite overgrows grains of chromite and uvarovite. Grains of the Fe-dominant mineral of the shuiskite group are noted.
Conclusions. Nephrite was formed through both metamorphic and metasomatic processes. Serpentinite was replaced by diopside, which was then replaced by nephrite. Metamorphism enhanced the metasomatism of the serpentinite melange and provided the cryptocrystalline tangled fibrous structure of the nephrite. Then metamorphism and metasomatism led to the formation of omphacite and cracking of the nephrite, which reduced its quality. As these processes progressed, the contribution of the crustal fluid increased, which is confirmed by the results of studying the oxygen isotopic composition of nephrite and other rocks of the deposit.
Ospinsk is an area in Russia well-known for mining the highest quality green nephrite in the world. However, the chatoyant green nephrite found here has not been studied to date. This study explores the mineralogy, geochemistry, and petrogenesis of chatoyant green nephrite collected from Ospinsk using polarizing microscope back-scattered electron images, scanning electron microscopy, Fourier transform infrared spectrometry, laser Raman spectroscopy, electron microprobe analysis, and laser ablation inductively coupled plasma mass spectrometry, and compares them with S-type green nephrite from other regions of the world. Tremolite is the main mineral constituent, and chromite, chlorite, graphite, and magnetite are accessory minerals in the samples. The chatoyant green nephrite from Ospinsk is serpentinite-related green nephrite. The Ti content of the chatoyant green nephrite from Ospinsk is significantly higher than that of green nephrite from other places. The chatoyant green nephrite deposit in Ospinsk is a contact metasomatic deposit related to ultramafic rocks. The ultramafic rocks first altered to serpentinite and later converted to tremolite after repeated thermal contact-based metasomatism. During the metasomatism of serpentinite into green nephrite, unilateral, compressive, and shear stresses caused by obduction forced directional growth of tremolite, resulting in chatoyancy.
