Abstract: There is a very peculiar type of bedded siliceous rock occurred in the Gufeng Formation of the Lower Permian in the Hushan of Nanjing, jiangsu Province and the Pingdiangshan, Anmenkou of the northern Chaohu, Anhui Province. The Gufeng Formation is dominated by a suite rock, usually grey of light yellow in color, is intercalated with bedded radiolarian chert or shales. It is characyerized by soft and porous nature, and looks like shle or diatomite at the surface outcrops. It can be seen under the microscope that the rock contains a large amount of rhombic and irregular cavities surrounded by siliceous cement consisting of microquartz. Sometimes small amount of calcite presents in the cements either as scattered crystals or as small irregular aggregates. Occasionally, residual calcareous bioclasts can also be found in the rock. Observation with SEM closed by fine anhedral micoquarrtz crystal. Only a few appear to be euhedral crystals. The chemical analysis date demonstrate that these porous siliceous rocks from the Gufeng Formation in northern Chaohu have a higher content of SiO2 (＞90%) and a very small amount of impurities. X-ray determination of the porous rock indicates that it consisted almost entitely of quartz. The preliminary study suggests that this is a siliceous rock originated by replacement of sedimentary carbonates, such as dolomitic limestone. The pores correspond to the casts of euhedral dolomite rhombs contained in a dolomitic limestone and at a later time dissolved out. Since the rock similar to the “chert nectique” (Cayeux,1929) in composition and feature of porosity, the authors proposed to name it nectic chert.