Gold-Silver ratios of electrum from the Fire Creek deposit of Lander County, NV (USA), were quantified using X-ray mapping and spot analysis with EPMA (Electron Probe Microanalysis). The Fire Creek deposit produces high-grade gold and silver ore from a series of mid-Miocene high angle veins and faults hosted in basaltic-andesite along the western margin of the Northern Nevada Rift. This shallow, lowsulfidation epithermal deposit has produced about 530,000 Troy ounces of gold with average grade

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... f 0.68 oz/ton since underground mining commenced in 2016. The majority of gold and silver mined here occurs as electrum, naumannite, and acanthite hosted in banded and brecciated quartz ± calcite ± adularia ± clay veins ranging from 0.07 to 1.83 m wide (Type I ore). Additional gold and silver resources hosting refractory ore have also been mined and identified. Here, ore occurs as Au and Ag in pyrite, marcasite, and arsenopyrite that are hosted in heavily clay altered rocks and fault gouge (Type II ore).