The Uzelginsk deposit in the southern Urals, in Russia, is an example of a weakly altered classical massive sulfide deposit of the Uralian type. Pyritic Cu-Zn ore contains gold in two main modes: so-called "invisible" gold in sulfides, and mineral forms represented by native gold and tellurides. Gold and PGE concentrations in sulfides from the Uzelginsk deposit have been determined by instrumental neutron-activation analysis (INAA) and wet-chemical analysis with chromatographic and ICP-MS determinations in parallel. Most of the gold occurs invisibly in pyrite and in chalcopyrite, and ranges from 0.7 to 20 ppm and from 1 to 18 ppm, respectively. Sphalerite bearing fine-grained emulsion-like inclusions of chalcopyrite contains 1.8 to 10.6 ppm Au. The gold content of pure grains of sphalerite, as detected by INAA, is between 0.3 and 3 ppm. Tennantite is the main host of Ag; low-iron tennantite (0.1-0.6 wt.% Ag) is the dominant variety, whereas Ag-bearing tennantite (up to 8.4 wt. % Ag) is scarce. Considerable PGE enrichment (up to 354 ppb Pt, 1220 ppb Pd and 707 ppb Rh) was determined in heavy-mineral concentrates from Au-rich mineralization above the quite low levels of PGE background in the ore. Metamorphism of sulfide ores resulted in the redistribution of non-ferrous and precious metals and the formation of submicrometric inclusions of Au-Ag alloy and Au compounds with Te, Se, S, As, Sb and Hg. Some PGE are hosted by pyrite and may be sent to the tailings during processing; the remainder was deposited from a hydrothermal fluid during metamorphism and enriched the products of the latest paragenesis. Sulfide precipitation is shown to have occurred under conditions favorable for the incorporation of gold in solid solution in these minerals at high temperature (250-380 C). The paragenesis of native metals (gold, silver, tellurium and rhenium), tellurides and sulfosalts was formed at the latest stage of the hydrothermal processes, at 165-190 C. SOMMAIRE Le gisement de Uzelginsk, dans le secteur sud des Ourales, en Russie, est un exemple d'un amas classique de sulfures massifs à faible degré d'altération de type Ouralien. Dans le minerai pyritique à Cu-Zn, l'or se présente de deux façons, soit l'or dit "invisible", dans les sulfures, et l'or dans une expresion minéralogique, par exemple l'or natif ou sous forme de tellurures. Les concentrations de l'or et des éléments du groupe du platine (EGP) dans les sulfures de ce gisement ont été établies par activation neutronique et par analyses par voie humide, avec déterminations chromatographiques et par ICP-MS en parallèle. La plupart de l'or est invisible dans la pyrite et la chalcopyrite, entre 0.7 et 20 ppm, et entre 1 et 18 ppm, respectivement. La sphalérite montrant une émulsion d'inclusions très fines de chalcopyrite contient entre 1.8 et 10.6 ppm Au. La teneur en or de la sphalérite pure, telle que détectée par activation neutronique, se situe entre 0.3 et 3 ppm. La tennantite serait l'hôte principal de l'argent; la tennantite à faible teneur en fer (0.1-0.6% Ag, poi...

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The first occurrence of new mineral ardaite (a chlorine sulphosalt) has been discovered in the Madjarovo polymetallic ore deposit (Bulgaria). The average composition is Pb 56.50, Ag 0.04, Sb 22.48, S 15.56, Cl 3.78, total 98.36 wt.%. The formula is Pb20–18 Sb12–24S34–36.5Cl6–8. The mineral occurs as fine acicular aggregates associated with galena, nadorite, a Cl-bearing robinsonite and Cl-beating semseyite, pyrostilpnite, silver- bearing tetrahedrite and anglesite.

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