AN ELECTRON MICROSCOPY STUDY OF GOLD FROM ROUND MOUNTAIN

Much attention has been given to gold nanoparticles, both natural and synthetic, because of their unique physical and chemical properties. One topic of interest to geologists is the role that gold nanoparticles (colloidal gold) play in the formation of epithermal gold deposits. While the role that transport and aggregation of colloidal gold plays in epithermal systems has been studied, much remains unknown. This study analyzed macroscopic gold samples from the Round Mountain Gold Mine in Nevada using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Microtopographic evidence from SEM indicates that two dimensional nucleation and growth is the dominant growth mechanism for macrocrystalline gold. TEM analysis suggests that nanoparticles are common in the Round Mountain gold and that these nanoparticles may have played a crucial role in the formation of macrocrystalline gold. This study also noted the presence of gold nanoparticles locked in other mineral phases, such as titanium oxide, adularia, and illite/sericite. The presence of these nanoparticles may represent a refractory ore component from which gold is unable to be recovered using current extraction practices, decreasing overall extraction efficiency. Results from this study warrant further electron microscopy investigation of this, and other epithermal deposits.