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天然紫晶与合成紫晶的鉴别是国内外珠宝鉴定实验室的一个难题,前人主要从双晶、色带、包裹体、红外吸收光谱特征等方面开展了研究。在利用红外光谱鉴别天然紫晶与合成紫晶时,不同的学者尚对3595cm-1或3543cm-1吸收峰作为诊断性还是指示性的判据存在不同认识。本文系统采集了典型的天然紫晶与合成紫晶样品,研究了利用红外光谱测试技术鉴别天然紫晶与合成紫晶的局限性,并尝试将偏振拉曼光谱应用于紫晶成因鉴别。结果表明:利用3595cm-1、3543cm-1红外吸收峰进行紫晶鉴别仅具有指示性意义,不能作为决定性的判定依据,偏振拉曼光谱可作为重要的补充。天然紫晶的偏振拉曼光谱(偏振方向:HH)均出现400cm-1的拉曼峰,而该峰在合成紫晶偏振拉曼光谱中缺失;合成紫晶的偏振拉曼光谱(偏振方向:HH)均具有795cm-1、448cm-1的拉曼峰,而这两个峰在天然紫晶偏振拉曼光谱中缺失。偏振拉曼光谱产生差异的原因可能与天然紫晶和合成紫晶内部晶格变形程度的不同有关。本文揭示的400cm-1、448cm-1和795cm-1偏振拉曼峰可作为鉴别紫晶成因的新依据。 相似文献
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紫色翡翠是天然翡翠中的重要品种,具有很高的经济价值,其主要有2种类型,一种呈较纯的紫色,另一种为带有蓝色色调的紫色。为探究紫色翡翠的致色机理,除采用传统的谱学及化学成分分析外,本文重点采用电子顺磁共振(EPR)、X射线光电子能谱(XPS)等,对2种类型紫色翡翠致色机理、致色元素价态等进行深入研究。结果表明,2种类型紫色翡翠均为硬玉颗粒本身呈色。紫色样品致色与Mn有关(w(Mn O)=0.0035%～0.036%),紫外可见光吸收光谱具有由Mn导致的580 nm吸收带,电子顺磁共振分析显示其主要为Mn~(3+),而并非Mn~(2+)。蓝紫色翡翠由Fe、Ti元素联合致色(w(Fe O)=0.039%～0.25%;w(Ti O_2)=0.018%～0.17%),X射线光电子能谱分析显示其主要致色离子为Fe~(2+)、Fe~(3+)和Ti~(4+),认为蓝紫色翡翠为Fe~(2+)-Ti~(4+)和Fe~(2+)-Fe~(3+)电荷转移致色,由此导致紫外可见光吸收光谱中具530和610 nm的吸收带。 相似文献
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天然宝石和合成宝石的鉴别标志 总被引：1，自引：0，他引：1
张传荣 《矿物岩石地球化学通报》1989,(3)
宝石可分为四类:天然宝石(包括处理宝石)、合成宝石、人造宝石和假宝石。自然界中已发现的矿物约3100种,可作为宝玉石的天然矿物有230种(包括它们的种、变种、族).比较重要的近百种,如钻石、红蓝宝石,祖母绿、海蓝宝石、紫晶、翡翠、绿松石等。合成宝石是一种与天然矿物相应的人工复制品,具有相同的化学成分和物理性质。主要种类有合成的钻石、红蓝宝石、祖母绿、尖晶石、绿松石、黄玉、水晶、蛋白石、孔雀石等. 相似文献
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紫色“山仔濑石”为寿山石的一种，是一种由层状硅酸盐矿物组成的黏土质玉石。其表层风化为黄色，内部为紫色，属于图章石中较为稀少的颜色品种。本文采用常规的宝石显微镜对其外观特征进行详细观察；利用X射线粉晶衍射仪、显微激光拉曼光谱仪、扫描电子显微镜、激光剥蚀等离子质谱仪等对其矿物组成、化学成分、稀土元素特征及谱学特征进行测试；利用全岩化学分析、紫外-可见光分光光度计、SPSS分析模型对其颜色成因进行研究。结果发现紫色“山仔濑石”的主要矿物组成为伊利石，次要矿物为独居石、磷钡铝石、赤铁矿和重晶石；其稀土元素指示性数据呈现出轻稀土元素富集，重稀土元素亏损的现象，指示其矿物成因与还原的酸性热液蚀变有关；紫色“山仔濑石”的紫色色调深浅与伊利石中Mn含量高低呈现正相关性；紫色“山仔濑石”内主要矿物和次要矿物的种类、分布特征和形成温度的不同说明在成矿后期存在多期热液侵入，紫色“山仔濑石”的形成过程与寿山地区的成矿规律具有一致性。 相似文献
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辽宁金伯利岩中镁铝榴石与金刚石的关系 总被引：1，自引：0，他引：1
辽宁金伯利岩中镁铝榴石的含量与金刚石的含量成正比。富含矿的岩体中镁铝榴石颜色有紫色、红色和橙色等种类,其中以紫色的为主,金刚石的含量越多紫色类型所占比例就越大。 镁铝榴石中Cr_2O_3和CaO的含量随其颜色的加深而升高;Al_2O_3、MgO、TiO_2的含量变化则相反。富矿岩体中富铬(>5％)镁铝榴石的含量高于中等含矿和贫含矿的岩体。 文中还列出了山东和贵州金刚石矿中镁铝榴石的资料以资对比。 相似文献
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利用北京正负电子对撞机（ＢＥＰＣ）提供的同步辐射（ＳＲ）白光为激发源（束斑尺寸１００μｍ×１００μｍ，计数时间１００ｓ／点），研究了蓝宝石、红宝石、紫晶、祖母绿的天然、加工和合成品的微量元素成分，对于鉴别宝石提供了有益的信息。 相似文献
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玛瑙:适宜温水清洗液,但不可浸泡。紫晶、黄晶类:适宜温水清洗液,避免高温。海蓝宝石、蓝色绿柱石:温水清洗液,避免热与强光。金绿宝石、猫眼:温水清洗液。钻石:温水,含氨清洁剂一滴,不可碰撞,避免与动物脂和皮肤油接触。祖母绿:温水清洗液或柔软湿布,不可浸泡,环境须干燥。 相似文献
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S. Karampelas E. Fritsch T. Zorba K. M. Paraskevopoulos S. Sklavounos 《Mineralogy and Petrology》2005,85(1-2):45-52
Summary The infrared absorption spectrum of amethyst in the region of stretching vibrations of X–OH groups reveals several bands that
have been used for the separation of natural from synthetic amethyst. The intensity and shape of these bands have been measured
as a function of crystallographic orientation. Using a resolution of 0.5 cm−1 the 3595 cm−1 band is present in all infrared spectra of natural amethyst and in some rare synthetic ones. If present in synthetic amethyst,
its full width at half maximum (FWHM) is about 7 cm−1 whereas it is about 3 cm−1 in all natural samples. This new criterion, unlike the previous ones, seems appropriate to separate natural from synthetic
amethyst in all cases. 相似文献
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In natural amethyst samples subjected to shock pressures between 10 and 50 GPa (1 GPa=109 Pa), thermoluminescence (TL) was observed after subsequent X-ray irradiation, in some cases even without high energy irradiation. The glow curves could be decomposed into at most five components of Gaussian shape, but no reliable activation energies could be determined from them, perhaps due to a wide distribution of trap depths. With increasing shock pressures traps of higher thermal stability were favored. Emission bands with maxima near 14000 cm?1 were observed independent of shock pressure. They appear to be characteristic of defects created during the shock events, but it is uncertain whether the observed TL is connected with the iron impurities characteristic for amethyst. In natural amethyst samples of the same origin no TL could be observed, even after additional X-ray irradiation. It is concluded that TL in amethysts reported in the literature was actually caused by defects associated with aluminium impurities, not by destruction of Fe4+. 相似文献
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H. Albert Gilg Yves Krüger Heinrich Taubald Alfons M. van den Kerkhof Martin Frenz Giulio Morteani 《Mineralium Deposita》2014,49(7):861-877
Fluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Paraná continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low δ34SV-CDT values of pyrite (?25 to ?32?‰) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in δ18O values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80–90 °C infiltrating a basaltic host rock of less than 45 °C. Colourless quartz and amethyst formed at temperatures between 40 and 80 °C, while the different calcite generations and late gypsum precipitated at temperatures below 45 °C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with δD values of amethyst-hosted fluid inclusions (?59 to ?51?‰) show a significant 18O-shift from the meteoric water line. This 18O-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high δ34S values of anhydrite and barite (7.5 to 9.9?‰) suggest that sedimentary brines from deeper parts of the Guaraní aquifer system must have been responsible for the amethyst mineralisation. 相似文献
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Giulio Morteani Y. Kostitsyn C. Preinfalk H. A. Gilg 《International Journal of Earth Sciences》2010,99(4):927-947
The amethyst-bearing geodes found in the flood basalts of the Arapey formation at Artigas (Uruguay) were formed as protogeodes
by bubbles of CO2-rich basalt-derived fluids. The formation of the celadonite rim and the lining of the geodes by agate followed by quartz
and amethyst were driven by the artesian water of the Guaraní aquifer percolating the basalts from below. The temperature
of the amethyst formation is estimated from fluid inclusion data to be between 50° and 120°C. Oxygen stable isotope data suggest
a crystallization temperature of calcite of about only 24°C. The actual wellhead temperature of the water produced from the
Guaraní aquifer in the study area is around 29°C. 相似文献
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The occurrence of the amethyst-citrine dichromatism in natural and mainly synthetic quartz crystals was studied as a function of their growth conditions. It has been found experimentally that the origin of the coloration is related to the variable dependence of the incorporation of the amethyst- and citrine-producing impurities on the crystallographic direction and growth rates of the faces and also to the effect the charge compensators have on the thermal stability of the amethyst color centers. 相似文献
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Adriane Commin-Fischer Gilles Berger Mireille Polvé Michel Dubois Paul Sardini Daniel Beaufort Milton Formoso 《Journal of South American Earth Sciences》2010,29(3):751-760
The filling process of amethyst-bearing geodes from Serra Geral Formation basalts, Brazil, is investigated by different methods performed on the SiO2 filling phases. Image analysis of quartz–amethyst deposits suggests a single growing mechanism ruled by geometric selection of randomly oriented crystals. Microthermometry of fluid inclusions reveals formation temperature lower than 100 °C, probably lower than 50 °C, and fluid salinity as high as 3 mass% NaCl eq. Composition in REE and trace-elements measured by ICP-MS on acid-digested or laser-ablated samples indicates a common genesis for amethyst, quartz and chalcedony, as well as the absence of significant variations from one geode to another. 87Sr/86Sr data on chalcedony shows that both the host basalt or the Botucatu sandstone are possible silica sources. These data, combined with thermo-kinetic considerations, permit us to discuss the filling process. We argue in favor of the contribution of a mineralized fluid of hydrothermal origin producing a regional silica source which decreased with time. The observed mineral sequence is related to the depletion of silica in the solution. 相似文献
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Thousands of silica gossans are exposed at the top of the Lower Cretaceous basalt hills in the Paraná volcanic province, strongly indicating the presence of calcite, amethyst and agate geode deposits along with native copper mineralization. The Embrapa silica gossan in the northwestern portion of the province (Campo Grande region) is an excellent example of such novel geological structure in the continental flood basalts. This silica gossan has a size of 450 × 350 m standing out as a treeless area in the densely wooded savanna and makes part of the stratigraphy of six basalt flows of Paranapanema intermediate-Ti chemical type. The base of the volcanic column is constituted by two Pitanga types and the overlying column is Paranapanema type. Every basalt flow has a silicified sand layer or breccia at the top and these are fed by abundant sand dikes. The Anel Viário Norte (AVN) flow is the most intensely altered by hydrothermal fluids producing voluminous secondary calcite infillings in the amygdales and fractures. In this region the basalts contain higher copper content than the average of the volcanic province. The studied silica gossans display negative anomalies in gamma spectrometry as a response to K, U and Th depletion during alteration. We propose a new exploration methodology by observing GoogleEarth images complemented with field studies and geochemistry to readily locate favorable areas for amethyst and agate geode deposits and native copper mineralization. 相似文献