XRD and IR analyses show that the main phase of Xiangtan manganese ore from Hunan Province which contains manganese oxides is monoclinic cryptomelane. The accurate crystal_chemical formulae of natural samples 1#and 2#are (K0.51Na0.13Ca0.027)(Al0.168Fe0.091Zn0.046P0.043Ni0.027Ti0.021Mg0.016) Mn2+0.162Mn4+7.452 O16and (K0.57Na0.034Ca0.018)0.622(Mn7.695Ti0.022Cu0.02Ni0.02Zn0.006Al0.003)7.766, respectively, which are calculated by the combination of the magnetic system and electron microprobe analyses. This cryptomelane belongs to nano grade particles because the diameter of its crystal particles is between 30nm to 110nm as shown by Atomic Force Microscope (AFM). The parameters of crystal cell area0=0.9803 nm,b0=0.2849 nm,c0=0.9665 nm,β=91.2°, which are given by the correction of the Reitveld Powder Diffraction Profile Fitting Technique.There are two kinds of tunnels in the crystal structure, and K+ions are located in the larger tunnels constructed by [MnO6] octahedrons. Generally, the crystal_chemical characteristics of natural cryptomelane possess five favorable environmental properties, i.e., surface adsorption, redox, ion exchange, tunnel and nano particle effect.