'Freibergite Subgroup' (not an IMA approved species)
Formula:
(Ag6,[Ag6]4+)(Cu4C22+)Sb4S12S0-1
Comments:
According to Zhou (1994), argentian tetrahedrite is relatively abundant here, but freibergite does not occur. Sun (1996) only reports freibergite, but does not provide analytical data to confirm this.