缅甸硅化木的宝石学特征及其开发前景

硅化木是古代树木经地质作用而形成的木化石,其主要化学成分为SiO2。采用偏光显微镜和红外光谱仪对缅甸硅化木样品进行研究,结果发现,其有两种类型,一种为玉髓硅化木,主要由隐晶质石英和少量的粒状石英组成,折射率为1.54,密度为2.52 g/cm3,摩氏硬度为6.6,其内部有深棕色和白色絮状包裹体,红外光谱特征吸收峰为1 088,556.1,462.8 cm-1;另一种为蛋白石硅化木,主要由蛋白石组成,含有少量的隐晶质石英,折射率为1.45~1.46,密度为1.92~2.07 g/cm3,摩氏硬度为4.95~5.17,从其纵切面上可见排列整齐的木质纤维结构,横切面上呈细小孔洞状,其中一些已经转变为玉髓硅化木,红外光谱特征吸收峰在1 102,787,474 cm-1附近。据初步分析,缅甸硅化木具有良好的开发前景。

Gemmological Characteristics and Exploitation Prospects of Silicified Wood from Burma

Silicified wood is wooden fossil from ancient tree formed by geological process and mainly consists of SiO2. The silicified wood samples from Burma are studied by using polarized microscope and infrared spectroscope. The results show that there are two types, one is chalcedony-type silicified wood, which consists of cryptocrystalline quartz and a little granular quartz, with refractive index of 1.54, density of 2.52 g/cm^3 , hardness of 6.6, and darkbrown and white floccule inclusions. A group of IR absorption peaks are at 1 088, 556.1, 462.8 cm^-1. The other is opalline-type silicified wood which consists of opal and a little cryptocrystalline quartz, with refractive index of 1.45-1.46, density of 1. 92-2.07 g/cm^3, hardness from 4.95 to 5.17. It is of woody fibrous structure orderly in the vertical-section and small pore space in the across-section. Some of the opaline-type silicified wood have changed to chalcedony-type silicified wood. A group of IR absorption peaks are at 1 102, 787, 474 cm^-1. It is considered primarily that the silicified wood from Burma has the favorable exploitation prospects.