Abstract:In this paper, a series of color shades of Taiwan original nephrite stones were studied in the aspect of chemical composition and structural changes of minerals so as to explore the color-causing mechanism. Taiwan nephrite is dominated by tremolite with a small amount of chlorite, and assumes significant felt-like fibers-interwoven metacryst structure. Mineral composition analysis shows that, with the change of the sample color from blue and white through blue-green, green to dark green, the MgO percentage of tremolite varies in order of medium→low→high, and FeO percentage content of tremolite varies in order of low→high→medium. In addition, the content of Cr₂O₃ shows a decreasing trend. Raman spectra show that, with the darkening of color samples, low frequency Raman bands position drifts to lower wavenumber (Fe²⁺ substitution for Mg²⁺ is enhanced).

Abstract:Mineralogical and chemical compositions of jade from Luodian area of Guizhou Province were studied in this paper. According to the appearance, the jade can be divided into white jade, grayish white jade, light greenish white jade, sapphire and speckled jade. The structure of Luodian jade observed under the microscope is fibrous-columnar metacrystal intertexture, fibrous-pilotaxitic metacrystal intertexture, and fibrous metacrystal intertexture, with obvious zonation. The electron microprobe analysis of the major mineral amphibole in white jade, grayish white jade, light greenish white jade, sapphire and speckled jade shows that amphibole is the tremolite in calcic amphibole group. According to the Si-Ti variation and genetic type classification diagram of calcic amphibole, this mineral falls into the area of altered and metasomatic amphibole. According to the combination and genetic classification of Ca-Mg-Fe in clinopyroxene and the nomenclature, It can be known that the pyroxenes from the Luodian jade deposit are mainly diopside with a small amount of sahlite.

Abstract:The Yurungkax River and Karakax River (White Jade and Black Jade) are two main placer nephrite sites located in Hetian, Xinjiang. They are well known historically for their valuable white, green and black nephrite, respectively, with a long history of use in the world. In this study, electron microprobe (EPMA) analysis was used to study green nephrite samples. The result shows that low Cr and Ni (Cr₂O₃ = 0.00 to 0.06% and NiO = 0.00 to 0.09%, respectively) are constant in these samples, consistent with the content of the marble-type nephrite but different from the content of serpentinite-related nephrite (Cr₂O₃ = 0.07% to 0.43% and NiO=0.08% to 0.36%). The accessory minerals in green nephrite include zircon, rutile, titanite and apatite which indicate the magmatic origin. According to petrographic study, several processes have been found in green nephrite: Di→Dol, Tr→Di, Tr→Tr, Chl→Tr. The homogenization temperatures for the inclusions in tremolite in green nephrite range from 200 to 400℃. Test data of the stable isotopes of the ore-forming fluid acquired at different temperatures show that the H and O isotopic values of green nephrite from the secondary deposit fall in the value range of existing marble-type nephrite, but are remarkably different from values of other serpentine-type nephrite deposits, as evidenced by a comparison with other types of nephrite deposits in the world. The results obtained by the authors show that green nephrite from secondary deposits was formed by contact metasomatism between magmatic rocks and marble, and that the ore-forming fluid was derived from magmatic hydrothermal fluid and precipitation.

Abstract:The mineralogical, gemological and spectral characteristics and chemical constituents of all kinds of green nephrite jade from Canada were studied by using slice observation, electron microprobe and infrared spectrum. The results indicate that the main mineral components are tremolite and actinolite, with actinolite being dominant. The green dots of green nephrite jade from Canada are chrome grossular, the black spots are chromite, and the waterlines are advanced tremolite.

Abstract:Russia is the main source of green nephrite in the world, and the green nephrite in the mining area around the Baikal Lake is of great fame. Recently, a new mineral area of green nephrite around the area of the Ospa Lake was found, whose market prospect is brisk. However, the lack of study in this field makes the research work a bit hard. In this paper, characteristics of mineral compositions and chemical components of green nephrite samples form Russia were studied by means of the conventional gemmological testing, X-ray powder diffraction, electron microprobe analysis and infrared spectra. The results indicate that the microtexture of Russia green nephrite is very compact. Its main composition component is tremolite. In addition, the black impurity in it is chromite. Its texture is mainly of the felt-like fiber interwoven metacryst mechanism,so the tenacity is very high. Russian green nephrite is different from green nephrite from New Zealand in composition and microtexture.

Abstract:Canada is one of the main producing areas of green nephrite, and there are three main mines in Canada: Polar, Cassiar and Kutcho; nevertheless, the qualities of green nephrite from different mines are different, but 1ittle research has been devoted to this diversity. In this paper, characteristics of mineral compositions and chemical components of green nephrite samples from Cassiar were studied by means of the conventional gemmological testing, orthogonal polarization microscope, electron microprobe analysis, X-ray powder diffraction and infrared spectrometer.The results indicate that the main mineral components of Cassiar green nephrite are tremolite and actinolite, together with minor quartz, whereas the black solid inclusions are iron-chromite and grossular, suggesting that the green nephrite from Cassiar of Canada is a product of the alteration of ultrabasic rocks. Its type is the same as that of the Manasi and the Hotan nephrite deposit. A comparison of the Cassiar mine with the Kutcho mine shows that the values of their main elements in green nephrite are different.

Abstract:In recent years, Russian green nephrite has entered Chinese market. Its gorgeous green color and nice quality are favored by many customers. In the previous study of Russian green nephrite, most samples were collected from the market, and hence the location wasn't specific; in addition, the study of the "water line" and "cat eyes" was very insufficient. Based on previous studies, the authors employed EMPA and LA-ICP-MS to study the mineralogy of green nephrite from Ospinsk of Russia and, on such a basis, discussed its color influencing ions. The results show that the main mineral composition of Ospinsk green nephrite is tremolite, and the black spotted impurities turn out to be chromite, surrounded by chlorite. The "water line" is composed of tremolite as well. Ospinsk green nephrite's brilliant green hue is mainly related to Cr element content, which can assume bright green color in 400～1 500 μg/g.

Abstract:In 2012, a new tremolite deposit was found near the main tremolite jade ore district in Donggang Village of Dahua. Microscopic analysis reveals that the main mineral composition of the amphibole deposit in Donggang Village is tremolite whose content is higher than 95% in general. The tremolite has relatively small particles and fairly delicate structure. Through REE and hydrogen and oxygen isotope analysis, the authors inferred the source of metallogenic material and hydrothermal origin, and considered that the Donggang Village tremolite deposit is a magmatic hydrothermal replacement deposit.

Abstract:Testing the ordinary gemological features and using methods of microscope optical observation, X-ray powder diffraction and electron microprobe analysis, the authors studied the structure, composition and color mechanism of Dushan jade from Nanyang, Henan Province. The results indicate that the primary mineral components of Dushan jade are zoisite, edenite, mica and plagioclase which has experienced alteration in various degrees. The celeste color is related to the mica which contains chromium, the green color of the greenish pink jade has something to do with epidote, the green part of the whitish green jade is actually the mineral diopside which contains masses of iron and chromium. The purple color is attributed to Ti- and Cr-bearing biotite and sericite in the Dushan purple jade. Zoisite in the pink jade that causes the pink color and black color is in connection with edenite. The color transitions of black Dushan jade is related to the alteration extent of plagioclase which also transforms to various minerals.

Abstract:Tiger's eye is also known as silicified crocidolite whose raw mineral is blue asbestos formed by later replacement of SiO₂. It is named for its similarity to trees in color and texture. The previous researchers have already preliminarily studied color genesis of tiger's eye. As tiger's eyes with different colors have various gemological characteristics, the authors made investigations to find the relationship between these characteristics, such as the relationship between the structure and the relative density, that between the color and the mineral components as well as chemical composition, and that between the structure and the special optical effect. In combination with previous achievements of color genesis of tiger's eye in specific producing areas both in China and abroad, the authors hope to draw a further conclusion. Such means as polarizing microscope, infrared spectrometer, X-ray diffraction (XRD) and X-ray fluorescence spectrometry were used to analyze the microstructures, chemical compositions, mineral components and chemical elements compositions of the samples of tiger's eyes. The results show that the four samples have fiber structures. The analysis of infrared spectrometer and X-ray diffraction (XRD) suggests that the samples consist of quartz, whose colors have nothing to do with quartz. Based on X-ray fluorescence spectrometry, the authors inferred the coloring mechanism. Specifically, the samples' colors are caused by iron precipitates among grains of quartz with fiber structure, and their color variations are related to various degrees of silicification of crocidolite. Among these samples, the blue sample has the silicification at the minimum level with a lot residual blue asbestos; the yellow one has the moderate silicification, in which aluminum is supposedly the secondary coloring element; the red one has the highest degree of silicification, which presents reddish brown color with a lot of iron precipitates. The green sample is dyed over a short period of time after acid pickling, in which the attachment of the dye is the same as that of the nonferrous mineral in other natural samples.

Abstract:More and more people are interested in the quartzite jade mainly due to its rich and varied material colors. However, very limited information is known, particularly on the coloration mechanism. This paper investigated various colored quartzite jades from Huoshan of Anhui Province and Longling of Yunnan Province. The distribution of colors, major elements and trace elements were analyzed by optical microscopic techniques, X-ray fluorescence spectrometer, and ICP-MS. It is found that the colored minerals exist mainly in the fractures and the grain boundaries of fine quartz crystals. The coloration was generated during the post-crystallization stage with the assistance of the iron oxides and hydroxides minerals.

Abstract:Tanghe color jade was discovered in Tanghe of Hebei Province. The authors selected representative samples and conducted an investigation. The research methods include microscopic observation, relative density measurements, quantitative analysis of X-ray powder diffraction pattern and infrared spectrum analysis. The composition of Tanghe color jade is very complex. According to the composition, they can be divided into four categories, namely, nephrite, diopside jade, agate and chalcedony and calcite jade. Combining the above findings with petrologic naming rules, the authors deal with the naming method for the nephrite that contains impurity minerals. At last, the authors propose some identification methods which are non-destructive or micro-damage to Tanghe colored jade.

Abstract:As a very special way in jadeite trade, gambling-jadeite has become a great challenge to the jadeite trade and a study item for its particularity. Enticed by the highest profit, some unscrupulous merchants have used all kinds of false means, especially the filling treatment which can hardly be seen through. The authors tested a piece of fake gambling-jadeite by means of gem-microscopy, ultraviolet fluorescence, and infrared spectrometers. The difference between the fake gambling-jadeite and the nature jadeite can help us to uncover the truth.

Abstract:A new kind of Jade named Jinshayu Jade has appeared in the gem market in recent years. The gemological, mineralogical and spectral characteristics of Jinshayu Jade samples were studied by using the polarizing microscope, electron probe microanalyzer (EPMA), X-ray powder diffraction (XRD) and Fourier transform infrared spectrometer (FTIR). The results show that the Jinshayu Jade, which contains quartzs, muscovites, and a small amount of gypsums or magnetites, is of allotriomorphic micrograined-fine grained heterogranular crystalloblastic texture and gneissic structure. The quartz content is up to 97.9%, while the muscovite content is less than 2.1%. The quartz in the samples has a high crystallinity index. Therefore, it is initially held that the Jinshayu Jade from Cenxi can be classified as a kind of red aventurine quartz.

Abstract:The most definitive testing method for the filled jadeite jade is infrared spectroscopy, because the presence of 3 036 and 3 058 cm^-1 peaks is characteristic of polymer impregnation. The rule applies to the filled quartzite. In the past years there emerged many filled gems such as aquamarine, tourmaline, garnet and feldspar. The experts identified filled gems according to the two peaks due to polymer. However, the authors note that many minerals have the peaks or bands from 3 100 to 3 000 cm^-1 of the FTIR absorption spectra and many gemstones absorb all the infrared light in that frequency range, so the peaks due to polymer might be covered up. The authors also warn that the gems impregnated with inorganic material would not present the absorbance from 3 100 to 3 000 cm^-1. Therefore, whether the FTIR spectra show the absorbance peaks at 3 036 and 3 058 cm^-1 or not, it is not the only, conclusive evidence that indicates whether the gems are filled or not. Different gems can't be compared absolutely with each other.

Abstract:The color of brown diamond from Mengyin of Shandong Province is caused by many factors. In order to verify the relationship between the brown color and the plastic deformation and analyze the characteristics of brown diamond under the transmission electron microscopy (TEM), the authors collected brown diamond samples from Mengyin Victory 1 rock tube, and made experiments on dislocation configuration of brown diamond, dislocation density and mineral energy spectrum under transmission electron microscopy (TEM) and X-ray energy spectrometer. The results show that there exists wafer nitrogen in the sample, demonstrating to some extent the dislocation configuration in darkened brown diamond of Shandong and suggesting that both the interaction between dislocations and the dislocation reaction types are very rich, and these characteristics are based on the premise of dislocation motion. Dislocation density shows in a sense that the diamond samples have a certain degree of plastic deformation, which provides some quantified reference for the connection between the brown color and the plastic deformation.

Abstract:In order to investigate coloration genesis and color change mechanism of HPHT synthetic diamond in a dynamic process, the authors conducted a HPHT experiment on yellow diamonds synthesized under the condition of high temperature and high pressure. IR spectra, low temperature PL spectra and DiamondView^TM images tested before and after the HPHT treatment show that, due to the limitations of the synthesis method, HPHT synthetic diamond has various kinds of defects, such as stress defect, vacancy and impurity elements like N and Ni. These defects greatly affect the quality and color of HPHT synthetic diamonds. The color centers of the tested samples before and after HPHT experiment are (N-V)^-, (N-V), H3, C center, (Ni-V)^-, Ni-N complexes and Ni^-. The experimental physical conditions (7 GPa, 1 480℃) we adopted contribute to accumulation of nitrogen in diamond crystal. And this accumulation reaction leads to the transformation of diamond type from Ⅰb (with a bit A aggregation)to Ⅰb+ⅠaA mixed type and is also helpful to the change of synthetic diamond's color.

Abstract:Since the 1970s, Brazil has been a consistent source of emerald. Emeralds are mostly produced from the states of Minas Gerais, Bahia, Goias. Now there is still steady production from the Itabira/Nova Era belt in the gem rich state of Minas Gerais. Along with successes there have also been challenges to the Brazilian emerald industry. Increasingly strict environmental regulations, higher labor costs have made production more expensive. Another challenging issue facing the mining, cutting, , trading sectors is the rapid rise of the Brazilian real against the U.S. dollar. The independent miners can't make a living on emerald mining for the mines were becoming too deep, it was difficult to work on the hard rock using h, tools at that depth. The cutters from Brazil are facing the challenge from Indian buyers who can offer a good price. Mining companies use advanced mining, sorting technology to reduce the cost of production, some mining companies cut its own rough emeralds, thus moving up the value chain, recording higher profits per tonne of ore mined. The cutters from Brazil only cut the emeralds of better quality, sizes, , this helps them stay competitive in the global market. Brazilian cutters have found a niche in fine-quality calibrated goods that are enticing manufacturers worldwide. This enables them to hit a profitable price point, , they can also cut larger, good-quality emeralds. The future of the Brazilian emerald industry looks very encouraging.

Abstract:Based on the formation environment and chemical composition of the turquoise,this paper has summarized the progress in the study of color emerging mechanism of the turquoise and the effect of the existing form of water on the color. Some constructive suggestions concerning the focal points in further research on the turquoise are also put forward.

Abstract:In this paper, the gemological, mineralogical and spectral characteristics of four kinds of imitation lapis lazuli samples collected in the jewelry market of Beijing were studied by such means as gem microscope, polarizing microscope, X-ray powder diffraction and Fourier transform infrared spectroscopy. The results show that the four imitation samples can be grouped into two categories, one is dyeing marble and the other is manmade stone. The latter imitations mainly composed of calcite, lapis lazuli and pyrite grains are cemented by epoxy resin and were made with the mold. Lapis lazuli and their imitations can be preliminarily identified according to visual observation and amplification research on their gemological characteristics. Furthermore, identification and distinction can be carried out by XRD and infrared spectrometer.

Abstract:The seal stone is a kind of artwork with historical and cultural characteristics of China. Main mineral components of traditional Chinese seal stone are clay minerals composed of kaolin group and pyrophyllite. Based on a discussion on the mineralization of the seal stone deposits, the authors hold that the deposits were generally formed in the island arc and epicontinental arc tectonic environment and the distribution of deposits were strictly controlled by volcanic apparatus with the ore-bearing wall rocks being Mesozoic intermediate-acid continental volcanics, especially tuffs. The ore-forming material was derived from the wall rocks, and the hydrothermal solution came from the meteoric water. The stability of minerals such as pyrophyllite, kaolinite and sericite depended on the pH, the type of cations and the cation concentration of the aqueous media. A metallogenic model for seal stone deposits has been established in association with the research work of related seal stone deposits.

Abstract:Many Chinese freshwater and marine pearls are treated by radiation and dye in the pearl market to imitate Tahiti pearls. It is important for gems labs and jewelry business to identify Tahiti pearls, irradiated freshwater cultured pearls, black dyed Chinese freshwater and marine pearls easily and accurately. Raman spectrum was used to observe theses pearls. According to the results, dyed freshwater and marine pearls show special peaks around 1 352 and 1 587 cm^-1 produced by dyeing material like Ag⁺. Tahiti pearls spectrum assumes peaks from 1 259 to 2 532 cm^-1 related to porphyria pigments peaks and conchaolin, while only weak aragonite υ₁ peak around 1 087 cm^-1 and υ₄ peaks around 702～705 cm^-1 exist in irradiated freshwater cultured pearls' spectra.

Abstract:Gold pearl is a kind of organic gemstone and also a treasure in Nanyang pearl. In order to make a comparison between aragonite and calcite and an analysis of the mixtures of different proportions, the authors tested the pearl brought from the market by using infrared spectrometer and Raman spectrometer nondestructively and also employing the destructive method of KBr pellet of infrared spectrometer and X-ray powder diffraction. The results show that CaCO₃ in gold pearl is aragonite rather than calcite. However, the IR spectrum and Raman spectrum of gold pearl studied in this paper are somewhat different from those of aragonite, which might be caused by the organic matter in the pearl.