 The epithermal gold deposits occurring in the Sanpoil volcanics terminate directly below the unconformity where the volcanics contact the base of the Klondike Mountain Formation or sometimes penetrate into the Formation's lowest unit.Hydrothermal sinter deposits are known from the lowest portions of the Formation and are thought to represent hydrothermal eruption areas.In general the lower portions of the Formation have a large amount of hydrothermal alteration, and areas around vents are rich in pyrite and silica.