New data on gersdorffite and associated minerals from the Peloritani Mountains (Sicily, Italy)

Gersdorffite, ideally NiAsS, and associated minerals from Contrada Zillì (Peloritani Mountains, Sicily, Italy) have been characterized through electron microprobe analysis and X-ray diffraction. Primary minerals, hosted in quartz veins, are represented by gersdorffite, tetrahedrite-(Fe), and chalcopyrite with minor pyrite and galena. Rare aikinite inclusions were observed in tetrahedrite-(Fe) and chalcopyrite. Gersdorffite occurs as euhedral to subhedral crystals, up to 1gmm in size, with (Sb,Bi)-enriched cores and (Fe,As)-enriched rims. Its chemical composition is (Ni0.79-0.95Fe0.18-0.04Co0.04-0.01)(As0.90-1.03Sb0.10-0.00Bi0.02-0.00)S0.98-0.92. It crystallizes in the space group P213, with unit-cell parameters aCombining double low line5.6968(7)gÅ, VCombining double low line184.88(7)gÅ3, and ZCombining double low line4, and its crystal structure was refined down to R1Combining double low line 0.035. Associated tetrahedrite-(Fe) has chemical formula (Cu5.79Ag0.07)ς5.86(Cu3.96Fe1.59Zn0.45)ς6.00(Sb3.95As0.17Bi0.03)ς4.15S13.06, with unit-cell parameters aCombining double low line 10.3815(10)gÅ, VCombining double low line1118.9(3)gÅ3, and space group I-43m. Its crystal structure was refined to R1Combining double low line0.027. Textural and crystallographic data suggest a polyphasic crystallization of gersdorffite under low-temperature conditions.