The members of the sartorite homologous series are complex sulfides Me 2+ 8N–16–2X Me 3+ 16+X Me + XS8N+8where Me 2+ is Pb and Me 3+ is As and Sb, whereas Me + is Ag and/or Tl. This paper presents calculation formulae for the homologue order N and for the separate substitution percentages for Tl + (As,Sb) ↔ 2Pb and Ag + (As,Sb) ↔ 2Pb substitutions. This enables one to evaluate the crystal chemistry and build a systematic classification of the sartorite homologues