Abstract: In order to study the distribution characteristics of nitrogen platelets in diamond crystals from Shandong Province, China, 116 pieces of gem quality diamond crystal samples are investigated by using FTIR.The surface microstructures related to the nitrogen platelets are observed by differential interference microscope.The results show that 80.2% of the diamond samples contain nitrogen platelets.The stripe-like etch figures parallel to100 directions on 111 planes are discovered on the surfaces of several brown octahedral diamond samples.These etch figures lie parallel to each other and vary in size.The microanalysis of the 111 planes show that there are stronger IR absorption peaks at 1 359-1 375 cm^-1in the diamond samples, revealing the existence of huge quantities of nitrogen platelets.Judging from their appearances and IR spectra, the formation of the stripe-like etch figures parallel to100directions on111planes may result from selective etching of the platelets.