Abstract: 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.