安徽歙县龙潭砚石板岩矿物谱学特征研究

Study on mineral spectral characteristics of ink stone slate in Shexian County,southern Anhui Province

安徽歙县龙潭歙砚砚石资源赋存于大谷运组上段黑色板岩内,主要岩石为粉砂质绢云板岩和含粉砂绢云板岩。在系统的岩矿鉴定基础上,对两种砚石板岩进行了扫描电镜观察、X射线粉末衍射分析和热重分析。结果表明:两种砚石板岩的矿物组成均为石英和长石,微观构造为显微千枚状构造;砚石板岩的主要矿物为石英、绿泥石和白云母。热重分析结果证明:绿泥石和白云母广泛存在于砚石中,导致该区板岩具有更高的密度,这些矿物使砚石兼顾了隔水性和研磨性,是歙县板岩成为高品质砚石的重要原因。高分辨带能谱SEM鉴定结果发现:微粒金属矿物主要为黄铁矿、黄铜矿及钛铁矿等,这些微粒金属矿物是歙砚最美大观“金星”的成因,而含粉砂绢云板岩比粉砂质绢云板岩的云母含量高,石质更细腻,品质更佳。

The ink stone deposit in Longtan area of Shexian County,Anhui Province occurred in the black slate of the Daguyun Formation,dominated by silty sericite slate and silt-bearing sericite slate.Based on systematic petrological and mineralogical identification,scanning electron microscope observation,X-ray powder diffraction and thermogravimetric analysis(TGA)were undertaken for the two types of ink stone slate.The results show that the mineral compositions of the rocks are quartz and feldspar,and the microstructure is microphyllum structure.The main mineral facies of the slates are quartz,chlorite and muscovite.Thermogravimetric analysis indicates widespread occurrence of chlorite and muscovite in ink stone,which results in a higher density of the slate in the area.The existence of these minerals makes the ink stone both water-repellent and abrasive,which are the important properties for that Shexian slate can be made into high quality inkstone.Through high resolution scanning electron microscope(SEM)identification,these metallic particles mainly contain pyrite,chalcopyrite,ilmenite,etc.,which are the origins of“Venus”,the most beautiful view of the ink stone.Compared with silty sericite slate,silt-bearing sericite slate has higher mica content,finer stone texture and better quality.