Abstract: Ore microscope and electron microprobe investigations on Zn-Pb-Ag ores from B Zone in Silvermines, Ireland, have shown the presence of two As-Sb-Ag phases; a tetrahedrite-group mineral with composition Cu_6.3Ag_3.7Fe_0.9Zn_1.2As_2.2Sb_2.1S_12.7 and proustite-pyrargyrite (Ag₃As_0.5Sb_0.5S₃). It is postulated that both phases inherited their As and Sb from primary geocronite (Pb_14.5As_3.4Sb_2.6S₂₃) and that they are metastable. An enrichment in Ni in the ores is due to very fine to submicroscopic intergrowths of gersdorffite (Ni_0.6Fe_0.4AsS) with geocronite and with galena.