水热法合成Paraíba色绿柱石的宝石学特征
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摘要
近期国际珠宝市场中出现一种Tairus水热法合成绿柱石,其颜色与含Cu、Mn的绿蓝色锂电气石(商业名称Paraíba碧玺)较为接近。采用常规宝石学测试手段,并结合电子探针、傅里叶变换红外光谱、紫外-可见吸收光谱等分析测试方法,就水热法合成Paraíba色绿柱石的化学成分、谱学特征及颜色成因等问题展开研究。结果表明,水热法合成Paraíba色绿柱石的颜色主波长为487.7~490.2nm,明度为17.1%~31.5%,彩度为47.8%~93.7%,折射率、双折射率和密度值均比天然绿柱石略高,内部具典型的微波状、阶梯状、交叉状、紊乱状及近平行生长纹理;化学成分以贫碱富铜、铁含镍为特征;六方环结构通道中Ⅰ型水分子和Ⅱ型水分子并存,其合频振动致特征近红外吸收谱带分别位于5 450、5 127、5 270cm-1处;此外还有一定量的矿化剂组分存在。最后对水热法合成Paraíba色绿柱石的呈色机理一并给予了探讨。
The appearance of a kind of synthetic beryl introduced into the market by Tairus Created Gems recently,is very similar to copper and manganese-bearing greenish blue elbaite tourmaline(referred to as"Paraíba"in the trade).Thus,the chemical compositions,spectrum characteristics and colouring mechanism of hydrothermal synthetic Paraíba-colour beryl samples were researched by using the conventional gemmological methods and modern analytical techniques including electron probe micro-analyzer(EPMA),Fourier transform infrared spectroscopy(FTIR)and ultraviolet-visible absorption spectrometry(UV-Vis).The results showed that the dominant wavelength,brightness and saturation(CIE 1931)of hydrothermal synthetic Paraíba-colour beryl samples are 487.7-490.2nm,17.1%-31.5% and47.8%-93.7% respectively.The refractive index and birefringence are 1.584-1.589and0.005,and density is 2.771-2.789g/cm3,which are slightly higher than natural beryl.The gemmological microscope investigations revealed that hydrothermal synthetic Paraíbacolour beryl exhibits typical growth patterns such as micro-wave,stair-step,cross,disorder and subparallel ones.EPMA analysis showed that the hydrothermal synthetic Paraíba-colour beryl is characterized by poor alkali(the content of K2 O and Na2 O content is generally below0.2%),rich copper(the content of CuO is higher than 5.00%)and iron(the content of FeOTis 1.76%-3.00%),and nickel-bearing(the content of NiO is 0.03%-0.15%).The FT-MIR spectra defined the vibration areas of silica tetrahedron group in six-membered rings.The symmetry and asymmetry stretching modes of O—Si—O and Si—O—Si mainly appear at 970,1 246cm-1 respectively.The FT-NIR analysis indicated that Type-Ⅰ and Type-Ⅱ water molecules are coexisting within the ring channel of hydrothermal synthetic Paraíba-colour beryl,and the absorption bands relating to the combination modes of type-Ⅰand type-Ⅱ H2 O mainly appear at 5 450,5 127 and 5 270cm-1.Besides,a certain amount of mineralizing agent used to synthetize beryl hydrothermally locates within the ring channel,and absorption bands appearing at 2 736cm-1 and 2 450cm-1 relating to chloridion are considered to be one of the identification characteristics of hydrothermal synthetic Paraíba-colour beryl.The UV-Vis spectra and EPMA results showed that the Paraíba-colour of hydrothermal synthetic beryl is mainly attributed to Cu2+,Fe2+,Fe3+and Ni 2+in the crystal structure.The Fe3+with 6A1g→4Eg(4 D)and 6A1g→4Eg+4A1g(4 D)d—delectron transition absorption bands appear at 370 nm and 426 nm.The Ni 2+with 3A2g→3T1g(3 P)d—delectron transition absorption band appears at 460 nm.A combination of the Cu2+with 2 E→2T2(2 D),the Fe3+with 6A1g→4T2g(4 G),the Fe2+with 5T2g→5Eg(5 D)d—delectron transition and Fe2+—Fe3+charge transfer absorption bands result in the strong absorption between 613-638 nm and 1 500 nm.
The appearance of a kind of synthetic beryl introduced into the market by Tairus Created Gems recently,is very similar to copper and manganese-bearing greenish blue elbaite tourmaline(referred to as"Paraíba"in the trade).Thus,the chemical compositions,spectrum characteristics and colouring mechanism of hydrothermal synthetic Paraíba-colour beryl samples were researched by using the conventional gemmological methods and modern analytical techniques including electron probe micro-analyzer(EPMA),Fourier transform infrared spectroscopy(FTIR)and ultraviolet-visible absorption spectrometry(UV-Vis).The results showed that the dominant wavelength,brightness and saturation(CIE 1931)of hydrothermal synthetic Paraíba-colour beryl samples are 487.7-490.2nm,17.1%-31.5% and47.8%-93.7% respectively.The refractive index and birefringence are 1.584-1.589and0.005,and density is 2.771-2.789g/cm3,which are slightly higher than natural beryl.The gemmological microscope investigations revealed that hydrothermal synthetic Paraíbacolour beryl exhibits typical growth patterns such as micro-wave,stair-step,cross,disorder and subparallel ones.EPMA analysis showed that the hydrothermal synthetic Paraíba-colour beryl is characterized by poor alkali(the content of K2 O and Na2 O content is generally below0.2%),rich copper(the content of CuO is higher than 5.00%)and iron(the content of FeOTis 1.76%-3.00%),and nickel-bearing(the content of NiO is 0.03%-0.15%).The FT-MIR spectra defined the vibration areas of silica tetrahedron group in six-membered rings.The symmetry and asymmetry stretching modes of O—Si—O and Si—O—Si mainly appear at 970,1 246cm-1 respectively.The FT-NIR analysis indicated that Type-Ⅰ and Type-Ⅱ water molecules are coexisting within the ring channel of hydrothermal synthetic Paraíba-colour beryl,and the absorption bands relating to the combination modes of type-Ⅰand type-Ⅱ H2 O mainly appear at 5 450,5 127 and 5 270cm-1.Besides,a certain amount of mineralizing agent used to synthetize beryl hydrothermally locates within the ring channel,and absorption bands appearing at 2 736cm-1 and 2 450cm-1 relating to chloridion are considered to be one of the identification characteristics of hydrothermal synthetic Paraíba-colour beryl.The UV-Vis spectra and EPMA results showed that the Paraíba-colour of hydrothermal synthetic beryl is mainly attributed to Cu2+,Fe2+,Fe3+and Ni 2+in the crystal structure.The Fe3+with 6A1g→4Eg(4 D)and 6A1g→4Eg+4A1g(4 D)d—delectron transition absorption bands appear at 370 nm and 426 nm.The Ni 2+with 3A2g→3T1g(3 P)d—delectron transition absorption band appears at 460 nm.A combination of the Cu2+with 2 E→2T2(2 D),the Fe3+with 6A1g→4T2g(4 G),the Fe2+with 5T2g→5Eg(5 D)d—delectron transition and Fe2+—Fe3+charge transfer absorption bands result in the strong absorption between 613-638 nm and 1 500 nm.
引文
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\[8\]周卫宁,张昌龙,陈振强,等.高档宝石晶体的水热法生长、宝石学特征及其发展前景---刚玉类和绿柱石类宝石晶体\[J\].人工晶体学报,2002,31(5):509-515.
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\[11\]石国华.桂林水热法合成祖母绿红外光谱特性及其意义\[J\].宝石和宝石学杂志,1999,1(1):40-46.
\[12\]亓利剑,夏义本,袁心强.合成红色绿柱石中通道水分子构型及1 H和23 Na核磁共振谱表征\[J\].宝石和宝石学杂志,2002,4(3):8-15.
\[13\]马尔福宁AS.矿物物理学导论\[M\].李高山,译.北京:地质出版社,1984:170-177,181-183.
\[14\]Gaite J M,Izotov V V,Nikitin S I,et al.EPR and optical spectroscopy of impurities in two synthetic beryls\[J\].Applied Magnetic Resonance,2001,20(3):307-315.
\[15\]Adamo I,Gatta G D,Rotiroti N,et al.Gemmological investigation of a synthetic blue beryl:A multi-methodological study\[J\].Mineralogical Magazine,2008,72(3):799-808.
\[16\]Schmetzer K,Schwarz D,Bernhardt H,et al.A new type of Tairus hydrothermally-grown synthetic emerald,coloured by vanadium and copper\[J\].The Journal of Gemmology,2006,30(1/2):59-74.
\[17\]邵慧娟,亓利剑,钟倩,等.俄罗斯富铁型水热法合成祖母绿特征研究\[J\].宝石和宝石学杂志,2014,16(1):26-34.
\[18\]Adamo I,Pavese A,Prosperi L,et al.Aquamarine,Maxixe-type beryl,and hydrothermal synthetic blue beryl:Analysis and identification\[J\].Gems&Gemology,2008,44(3):214-226.
\[19\]Abduriyim A,Kitawaki H,Furuya M,et al.“Paraíba”-type copper-bearing tourmaline from Brazil,Nigeria,and Mozambique:Chemical fingerprinting by LA-ICP-MS\[J\].Gems&Gemology,2006,42(1):4-21.
\[2\]张本宏,陈振强.天然与合成彩色绿柱石的致色和宝石学特征\[J\].宝石和宝石学杂志,2002,4(1):34-37.
\[3\]Gagan C,Chaman G.Gem news international:New Tairus synthetic beryl simulating“Paraíba”tourmaline\[J\].Gems&Gemology,2007,43(4):385-387.
\[4\]Gagan C.Tairus合成绿柱石的宝石学特征\[J\].黄艺兰,译.宝石和宝石学杂志,2009,11(1):28-30.
\[5\]王濮,潘兆橹,翁玲宝,等.系统矿物学\[M\].北京:地质出版社,1987:155-158.
\[6\]Wood D L,Nassau K.Infrared spectra of foreign molecules in beryl\[J\].The Journal of Chemical Physics,1967,47(7):2 220-2 228.
\[7\]Mashkovtsev R I,Solntsev V P.Channel constituents in synthetic beryl:Ammonium\[J\].Physics Chemistry of Minerals,2002,29(1):65-71.
\[8\]周卫宁,张昌龙,陈振强,等.高档宝石晶体的水热法生长、宝石学特征及其发展前景---刚玉类和绿柱石类宝石晶体\[J\].人工晶体学报,2002,31(5):509-515.
\[9\]闻辂.矿物红外光谱学\[M\].重庆:重庆大学出版社,1989:77-81.
\[10\]Aurisicchio C,Grubessi O,Zecchini P.Infrared spectroscopy and crystal chemistry of the beryl group\[J\].The Canadian Mineralogist,1994,32(1):55-68.
\[11\]石国华.桂林水热法合成祖母绿红外光谱特性及其意义\[J\].宝石和宝石学杂志,1999,1(1):40-46.
\[12\]亓利剑,夏义本,袁心强.合成红色绿柱石中通道水分子构型及1 H和23 Na核磁共振谱表征\[J\].宝石和宝石学杂志,2002,4(3):8-15.
\[13\]马尔福宁AS.矿物物理学导论\[M\].李高山,译.北京:地质出版社,1984:170-177,181-183.
\[14\]Gaite J M,Izotov V V,Nikitin S I,et al.EPR and optical spectroscopy of impurities in two synthetic beryls\[J\].Applied Magnetic Resonance,2001,20(3):307-315.
\[15\]Adamo I,Gatta G D,Rotiroti N,et al.Gemmological investigation of a synthetic blue beryl:A multi-methodological study\[J\].Mineralogical Magazine,2008,72(3):799-808.
\[16\]Schmetzer K,Schwarz D,Bernhardt H,et al.A new type of Tairus hydrothermally-grown synthetic emerald,coloured by vanadium and copper\[J\].The Journal of Gemmology,2006,30(1/2):59-74.
\[17\]邵慧娟,亓利剑,钟倩,等.俄罗斯富铁型水热法合成祖母绿特征研究\[J\].宝石和宝石学杂志,2014,16(1):26-34.
\[18\]Adamo I,Pavese A,Prosperi L,et al.Aquamarine,Maxixe-type beryl,and hydrothermal synthetic blue beryl:Analysis and identification\[J\].Gems&Gemology,2008,44(3):214-226.
\[19\]Abduriyim A,Kitawaki H,Furuya M,et al.“Paraíba”-type copper-bearing tourmaline from Brazil,Nigeria,and Mozambique:Chemical fingerprinting by LA-ICP-MS\[J\].Gems&Gemology,2006,42(1):4-21.