From the Senzai vein of the Oe mine situated in southwestern Hokkaido, some kinds of rhodochrosite stalagmites are sometimes found out at the bottom of druse within the vein. The stalagmites show the shape of column, 2 to 30mm in diameter and 1 to 12cm in length. They consist of irregular fan-shaped crystals superficially and show the solution growth textures such as concentric bandings. These stalagmites have the chemical compositions of 53 to 89 mole % MnCO₃, 2 to 20 mole % CaCO₃. 7 to 26 mole % FeCO₃ and 1 to 9 mole % MgCO₃, which are mostly within the compositional region of drusy rhodochrosite of the vein. Chemical compositions of the rhodochrosite stalagmites change markedly with the concentric bands as shown in Fig. 7, which shows considerable increase of MnCO₃ content from core to rim. This feature is considered as being due to chemical changes of the ore solution or ground water producing the rhodochrosite stalagmite.