The north-eastern section of Hanezuruyama consists of rocks which form part of the "Chichibu System" (Lower Permian); that is, the complex of diabase, schalstein, limestone, dolomitic limestone, dolomite and hornstone., First, the writer defines the terms dolomite, dolomitic limestone and magnesian limeston., He then recommends the AgNO 3-K 2CrO 4 method of distinguishing dolomitic limestone from the dolomite on polished surface, instead of applying "Lemberg's solution"., Second, the writer describes the microscopic characters and chemical analyses of some rocks., Finally, the writer concludes that the dolomite originates from an "authigenic sediment"., He asserts further that most of the limestones and the dolomites consist of carbnates derived from the activities of a submarine volcano, and that most of the liornstones consist of SiO 2 which is also a product of submarine volcanic activities.,