Abstract: Dypingite, Mg₅(CO₃)₄(OH)₂·5H₂O, was found in materials obtained during the production of high purity magnesia from crude magnesite by the calcination/CO₂-leaching process. The snow-white, finely crystalline dypingite contained 41.0% MgO; the theoretical value is 41.5%. The X-ray powder data revealed a long period structure with a strong peak at 31.0 Å. The five strongest reflections (Å) and their estimated intensities (I/I₀) were 10.4 (100), 31.0 (40), 15.62 (40), 5.86 (30), and 6.34 (20). The DTA curve showed ten endothermic reactions with maxima at 43, 50, 77, 86, 105, 127, 180, 260, 420, and 514°C and an exothermic reaction at 495°C.