Argentotetrahedrite- (Hg) (IMA 2020- 079), Ag6(Cu4Hg2)Sb4S13 is a new member of tetrahedrite-group of minerals found in the Dongping Hg- Ag deposit, Baojing County, northern section of the Hunan- Guizhou mercury metallogenic belt. It is the main ore mineral and recovery object of the deposit. A single crystal of argentotetrahedrite- (Hg) is around 5~20 μm, and occurs as granular and patchy agglomerate 20 to 300 μm in size. It occurs in association with tiemannite, metacinnabar, mercurian silver, andorite, miargyrite, stephanite, sphalerite and galena in quartz and calcite vein. Argentotetrahedrite- (Hg) exhibits a black colour with a reddish black streak and metallic lustre. The mineral is none fluorescence, magnetism and cleavage, brittle in tenacity, and has irregular fracture. The Morse hardness is 3~3. 5. The calculated density is 5. 578 g/cm3 on the basis of empirical formula and unit cell volume refined from single- crystal XRD data. The chemical composition is Ag 17. 79%; Cu 19. 65%; Hg 16. 17%; Zn 1. 01%; Fe 0. 37%; Sb 23. 56%; As 0. 36%; Se 0. 15%; S 20. 31%, total 99. 52%. On the basis of crystal refinement and total atoms=29 apfu, the crystal- chemical formula of argentotetrahedrite- (Hg) is Ag6 (Cu4Hg2)Sb4S13. According to the single crystal diffraction data of 1197 reflections, the crystal structure of argentotetrahedrite- (Hg) is determined (refinement factor R1=0. 0294). It is cubic, space group I4-3m, unit- cell parameters a=1. 06330(3) nm, V=1. 20217(11) nm3, Z=2. In argentotetrahedrite- (Hg), the tetrahedrally coordinated site S(1), the octahedrally coordinated site S(2), and the tri- pyramidally coordinated site X(3) are fully occupied by S and Sb respectively. The triangularly coordinated site M(2) is dominated by Ag+ (3. 39 apfu) over Cu+ (2. 61 apfu) and the tetrahedrally coordinated site M(1) is occupied by Cu+ (3. 96 apfu), Hg2+ (1. 56 apfu), Zn2+ (0. 29 apfu), Fe2+ (0. 19 apfu). It is characterized both by Ag dominance in M(2) and Hg dominance for charge compensation in M(1).