FIELD EMISSION SCANNING ELECTRON MICROSCOPY (FESEM) INVESTIGATION OF MACROCRYSTALLINE GOLD FROM EXCELSIOR MOUNTAINS IN NEVADA

Gold is well recognized as a global resource and exploration and extraction activities are being constantly refined to increase assets and promote wealth. The vast majority of gold occurs as disseminated deposits and macrocrystalline gold is comparatively rare. Nevada is the leading producer of total gold in the US however some mines and locations have macrocrystalline gold associated with these disseminated deposits. The mechanisms of formation of this macrocrystalline texture is poorly understood but if identified, may aid in the exploration of new properties with lower initial operational costs. Identifying textures in gold samples also may aid in developing new extraction techniques to improve recovery. Currently the extraction efficiency of gold mines in the State of Nevada is commonly around 75% leaving large amounts of gold in heap leach piles. A macrocrystalline gold sample from the Excelsior Mountains in Nevada was analysed in detail using field emission scanning electron microscopy (FESEM) techniques. A possible factor that determines the extraction efficiency of the gold is texture. Using SEM the gold sample was analysed to determine the variations in its texture. The sample material is electrum and it was found to have a variety of textures including steps and terraces with rounding along the edges, individual micrometer to nanometer scale particles and crystals in the surrounding gauge minerals. Complex textures suggest the presence of two generations of gold mineralization. The textures that were discovered are more complex than the generally accepted textures that are thought to be present on the surface of gold which indicates a more complex gold formational sequence. Textures observed show similarities to Round Mountain, Nevada macrocrystalline gold but are more complex having more variety with different textures being evenly distributed. Results indicate that gold texture varies significantly and mineralization processes may vary between mines in Nevada.