河北涉县石榴子石的宝石学特征

Gemmological Characteristic of Garnet from Shexian, Hebei Province

  • 摘要: 石榴子石是珠宝市场上常见的珠宝品种之一,同时也是重要的地质学、矿物学研究对象。本文研究样品来自于中国河北省邯郸市涉县符山铁矿,所属邯郸-邢台地区是我国有名的硅卡岩矿床区域,符山铁矿也曾以产出铁矿石和符山石闻名。通过常规宝石学测试、傅里叶红外光谱、激光拉曼光谱、紫外-可见光谱、电子探针、电感耦合等离子体质谱等测试方法对该地区石榴子石样品进行了测试和研究。结果表明,河北涉县石榴子石样品的矿物组分是以钙铝榴石为主的钙铝-钙铁榴石固溶体,具典型红外光谱及官能团区具有典型的结构水(OH-)的振动吸收; 拉曼光谱显示了以钙铝榴石为主,并含有Fe元素,Fe3+离子是主要的致色离子。河北涉县石榴子石样品的主量元素以Si、Ca、Al、Fe为主,钙铝榴石成分占端元组分70%以上,计算出其晶体化学式为(Ca2.850~2.977, Na0~0.002, Mn0.004~0.006, Fe0.161~0.2252+, Mg0.029~0.047)3.093~3.176(Cr0~0.002, Ti0~0.021, Al1.402~1.551, Fe0.102~0.2853+)1.624~1.825Si3.079~3.156O12。河北涉县石榴子石样品相对其他产地含有较多的Zr元素,可作为产地特征,同时可借助于丰富的Zr元素含量进行地质年代和地质成因的研究。

     

    Abstract: Garnet is one of the common jewelry varieties in the jewelry market, which is also an important geological and mineralogical research object. The samples studied in this paper are from Fushan iron ore mine in Shexian, Handan city, Hebei Province, China. The Handan-Xingtai area belongs to Fushan iron ore mine, which is a famous skarn deposit area in China. Fushan iron ore mine was also famous for producing iron ore and idocrase. In this paper, conventional gemmological test, Fourier transform infrared spectroscopy, laser Raman spectroscopy, ultraviolet visible spectroscopy, electron probe test (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to investigate the garnet samples from Shexian, Hebei Province. Based on spectroscopical tests and chemical composition analysis, the garnet samples from Shexian is mainly composed of grossularite and it is solid solution of grossularite and almandine. The typical IR transform spectra of grossularite can be observed, and the vibration absorption of structural water (OH-) is prominent in the functional group region. The Raman spectra of the garnet samples from Shexian are dominated by grossularite and iron occurrence, where Fe3+ ion is the main colour origin. The main elements of the samples are Si, Ca, Al and Fe. The grossularite component occupy for over 70% of the component. The crystal formula is (Ca2.850-2.977, Na0-0.002, Mn0.004-0.006, Fe0.161-0.2252+, Mg0.029-0.047)3.093-3.176(Cr0-0.002, Ti0-0.021, Al1.402-1.551, Fe0.102-0.2853+)1.624-1.825Si3.079-3.156O12.The garnet samples from Shexian, Hebei Province contain more Zr elements than the other producing areas, as well as the distinguishing features.Meanwhile, the rich content Zr of the garnet can be used for the geological origin study.

     

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