This study is focused on the characterization of Gatsuurt gold mineralization, Mongolia. The ores mainly consist of intergrown fine-medium grained (0.05-0.5mm) pyrite and arsenopyrite aggregates, and sphalerite, chalcopyrite, galena, native gold and tetrahedrite occur in pyrite and arsenopyrite. Pyrite is the most abundant sulfide. Early stage pyrite occurs in later stage pyrite as small grains of 20 μm in diameter. Sphalerite, chalcopyrite, galena, tetrahedrite and native gold are observed as inclusions in subhedral pyrite grains. Arsenopyrite occurs not only as aggregates with pyrite but also as euhedral grains in thin quartz veinlets. Sphalerite, chalcopyrite and galena occur as inclusions in pyrite, and their grains are very fine. Tetrahedrite is anhedral in form and has grain sizes up to 0.2mm. It is usually infilled by fractures of pyrite and arsenopyrite, and observed as inclusions that rarely coexist with native gold. Native gold is fine grained (5-50 μm in diameter), and present as rarely dispersed and as visible grains along their fractures in pyrite and arsenopyrite.
