Abstract: Chemical compositions of goldfieldite-tetrahedrite series minerals from the Iriki mine in Japan are reported for the frst time. The compositional variations of coexisting goldfieldite [atomic proportion Te > (Sb + As + Bi)], tellurian tetrahedrite [Sb > (Te + As + Bi)], and Te-free tetrahedrite from this locality are considered alongside data from the literature. These show that the substitution of (Sb, As)³⁺ for Te⁴⁺ in natural goldfieldite-tetrahedrite series minerals occurs by the following two mechanisms: (i) tetrahedrite, Cu10+(Cu,Fe,Zn)22+(Sb,As)43+S13and goldfieldite, Cu12+(Sb,As)23+Te24+S13 form a continuous solid-solution according to the coupled substitution of Cu⁺Te⁴⁺ for (Cu,Fe,Zn)²⁺(Sb,As)³⁺, and (ii) goldfieldite, Cu12+(Sb,As)23+Te4+S13 and the ideal end-member,Cu10+Te44+S13 might also form a continuous solid-solution by the coupled substitution of □(vacancy)Te⁴⁺ for Cu⁺(Sb,As)³⁺. According to this work, the general formulae of tellurian tetrahedrite and goldfieldite are, therefore, respectively, Cu10+x+(Cu,Fe,Zn)2−x2+(Sb,As)4−x3+Tex4+S13, with x = 0 to 2 and Cu12−y+Te2+y4+(Sb,As)2−y3+S13, with y = 0 to 2.