MANGANOQUADRATITE AND Cd-MANGANOQUADRATITE FROM SĂCĂRÂMB Au-Ag-Te ORE DEPOSIT, METALIFERI MOUNTAINS, ROMANIA

New investigations using optical microscopy, scanning electron microscopy (SEM) and electron-probe micro-analysis (EPMA) have been performed on samples of alabandite rich veins from the Sacaramb ore deposit, Metaliferi Mountains, in Romania. The second occurrence of manganoquadratite after Uchuccacua, Peru was discovered in Sacaramb, in the rhodochrosite filled veins which crosscut the massive alabandite. The mineral usually occurs as euhedral and subhedral crystals in the secondary carbonate veins that fill the open spaces in the massive alabandite. The average chemical composition of manganoquadratite from Sacaramb is Ag0.98Mn1.07(As0.94Sb0.08)(1.02)S-2.91(.) A Cd-manganoquadratite variety with a mean composition of Ag-0.94(Mn0.76Cd0.36)(1.12)(As0.94Sb0.04)(0.98)S-2.94 was also identified in the investigated samples. The presence of Cd in manganoquadratite indicates Cd-Mn substitution which could confirm the existence of an isomorphic series between quadratite and manganoquadratite. Manganoquadratite crystals that have Cd in their composition appear only in association with pyrite. The presence of Cd can be related to the chemical characteristic of pyrite crystals to adsorb Cd2+ from aqueous solutions.