白云母-金红石质图章石的矿物学特征  

MINERALOGICAL CHARACTERISTICS OF MUSCOVITE-RUTILE SIGNET STONE

作　　者：李金檑 刘云贵 LI Jinlei;LIU Yungui(Henan Open University,Zhengzhou,Henan 450046,China;School of Gems and Materials,Hebei GEO University,Shijiazhuang,Hebei 050031,China)

机构地区：[1]河南开放大学,河南郑州450046 [2]河北地质大学宝石与材料学院,河北石家庄050031

出　　处：《矿物岩石》2023年第2期11-17,共7页Mineralogy and Petrology

基　　金：国家自然科学基金(项目批准号:42103034)。

摘　　要：绿色图章石是我国众多图章石品种中的重要类别,四川“雅安绿”即为其中一个代表性的品种。近期国内珠宝市场出现了一种被称为“雅安绿”新亚种的图章石且广受关注,其外观为微透明的绿黄色基体上分布绿色半透明的纹脉,图案精美。本次研究采用偏光显微镜、X射线粉末衍射仪、电子探针仪、红外吸收光谱仪、激光拉曼光谱仪和紫外-可见光分光光度计对该种图章石的矿物组成、化学成分、谱学特征和颜色成因进行研究。结果表明,该图章石绿色纹脉的主要矿物成分为微晶白云母,绿黄色基体主要由微晶白云母和金红石组成,纹脉白云母中可充填有细脉状的绿泥石。明确了该图章石中白云母的多型类型为2M_(1)型,白云母的晶胞参数为a=0.514(2)nm、b=0.906(4)nm、c=2.015(6)nm、β=95.3(3)°,金红石的晶胞参数为a=b=0.460(2)nm、c=0.295(1)nm,计算其分子式为(K_(0.82)Na_(0.08))(Al_(1.80)Fe_(0.17)Mg_(0.03))(Al_(0.93)Si_(3.07))O_(10)(OH)_(1.94)。白云母在红外光谱低频区显示476 cm^(-1)、536 cm^(-1)、752 cm^(-1)、991 cm^(-1)等典型吸收峰,高频区OH伸缩振动引起的3627 cm^(-1)吸收峰伴随有明显的3655 cm^(-1)肩峰;绿色纹脉中白云母的拉曼光谱主要显示196 cm^(-1)、262 cm^(-1)和701 cm^(-1)等位移峰,基体中金红石显示446 cm^(-1)和610 cm^(-1)的拉曼位移峰。绿色纹脉白云母中Fe和Cr对于可见光的选择性吸收导致其呈现绿色,而基体部分在蓝紫区的强吸收和红橙区的弱吸收导致其呈现绿黄色。综合分析表明,该图章石与已报道“雅安绿”的矿物成分不一致,不应被归类于“雅安绿”,本次研究初步将其命名为白云母-金红石质图章石。Green signet stone is an important category among many kinds of signet stone in China.Recently,a new subspecies called“Ya'an green”signet stone has received much attention in domestic jewelry market.The appearance of this kind of rock is slightly transparent greenish-yellow matrix distributed with green translucent veins in exquisite patterns.In this paper,polarizing microscope,X-ray powder diffractometer,electron probe instrument,infrared absorption spectrometer,laser Raman spectrometer and UV-visible spectrophotometer are used to study the mineral composition,chemical composition,spectral characteristics and color origin of this kind of signet stone.The results show that the main mineral composition of the green veins is microcrystalline muscovite and the greenish-yellow matrix is mainly composed of microcrystalline muscovite and rutile with some finely-veined chlorite filled in the veined muscovite.It reveals that the polytype of muscovite is 2M_(1),the cell parameters of muscovite are a=0.514(2)nm,b=0.906(4)nm,c=2.015(6)nm,β=95.3(3)°,and the cell parameters of rutile are a=b=0.460(2)nm,c=0.295(1)nm.The molecular formula is calculated as(K_(0.82)Na_(0.08))(Al_(1.80)Fe_(0.17)Mg_(0.03))(Al_(0.93)Si_(3.07))O_(10)(OH)_(1.94.).Infrared spectra shows that the typical absorption peaks of muscovite in the low frequency region are 476 cm^(-1),536 cm^(-1),752 cm^(-1)and 991 cm^(-1),and the absorption peak of 3627 cm^(-1)caused by OH stretching vibration in the high frequency region is accompanied by an obvious 3655 cm^(-1)acromion.The Raman spectra of muscovite in green veins mainly show the displacement peaks of 196 cm^(-1),262 cm^(-1)and 701 cm^(-1),while those of rutile in matrix show 446 cm^(-1)and 610 cm^(-1).It is recognized that the selective absorption of Fe and Cr to visible light in green veined muscovite leads to its green color,while the strong absorption in blue-violet region and weak absorption in red-orange region in the matrix lead to its greenish-yellow color.Comprehensive analysis shows that the

关 键 词：白云母 金红石 图章石 雅安绿 矿物学特征 

分 类 号：P575[天文地球—矿物学]