摘要:
为系统探究南红玛瑙的宝石学特征,特别是红色纹带的成因,利用常规宝石学测试、X射线衍射分析仪(XRD)、扫描电子显微镜(SEM)、红外光谱仪(FTIR)、激光拉曼光谱仪(Raman)以及激光诱导等离子体光谱仪(LIBS)对南红玛瑙样品进行分析,确定南红玛瑙的矿物组成,分析影响南红玛瑙颜色的因素,试图解释及推测其条带的形成成因。结果显示,南红玛瑙样品的折射率为1.54~1.55,相对密度为2.642,隐晶质,可见贝壳状断口,玻璃光泽,紫外荧光灯下表现惰性。南红玛瑙主要矿物组成为石英,含有大量的Si,其次为Fe及少量的K、Ca、Al、Mg、Cl等,并且红色部分的鲜艳程度与Fe含量成正比,经拉曼光谱分析,红色部分中的Fe以赤铁矿形式存在。南红玛瑙的红带纹路成因可推测归纳为:岩浆液在空洞内周期性的结晶形成玛瑙,Fe在南红玛瑙中以独立铁质矿物(赤铁矿)形式存在,导致南红玛瑙呈现红色,并且每一期进入的铁矿物的含量不同,导致红色深浅不同,二者呈正相关关系。花纹方面,结晶速度适宜时喷入物可以充分分布,形成规整的平行条纹,当结晶速度很快,喷入物来不及均匀分布,便形成杂乱分布的纹路,常表现为火焰状。
关键词:
-
红玛瑙
/
-
宝石学特征
/
-
颜色成因
/
-
条带
Abstract:
The authors used X-ray powder diffraction (XRD), scanning electron microscope (SEM), infrared spectrometer, laser Raman spectrometer, laser induced breakdown spectroscopy (LIBS) and other modern advanced analytical instruments to study the mineral components of Nanhong agate in order to understand the influence factors of colour and to explain the formation of red stripes. The refractive index of Nanhong agate is about 1.54 to 1.55, and relative density is 2.642. These agates show no reaction under the ultraviolet lamps and show cryptocrystalline structure, conchoidal fracture and glassy luster. The major mineral component of Nanhong agate is quartz, with high content of Si, followed by Fe and trace elements such as K, Ca, Al, Mg and Cl. Furthermore, the intensity of red colour is directly proportion to the Fe contents. The laser Raman spectroscopy results show that the red parts show the presence of hematite. The reasons for the formation of the red stripes in Nanhong agate can be summarized as follows:the magmatic fluid in the cavity causes periodic crystallization of the agate. Fe is in the form of independent iron mineral (hematite), which makes the agate display red colour. And the higher iron oxide content, the deeper the red colour. In terms of pattern, when the crystallization rate is proper, the injected fluid can evenly distributed to form the parallel stripes. However, when the crystallization rate is too fast, the fluid does not have sufficient time to even distribution and thus it leads to the formation of messy lines which may look like flames.
下载:
