From 1936-1941 the Idaho-Maryland averaged gold recovery 95% by gravity and flotation methods.1
The majority of the gold at the Idaho-Maryland historically occurs as free gold particles in quartz and the mine previously recovered 67.5% of gold by gravity. Modern gravity separation equipment uses only water in the gravity separation process.
Gold mineralization at the Idaho-Maryland also occurs with sulphide minerals, primarily pyrite. Historically 27.5% of gold was recovered by sulphide flotation to a concentrate grading 3.9 oz per ton (134 grams per tonne). Rise would ship this sulphide concentrate off-site. Therefore, environmental issues related to sulphide minerals in sand tailings do not occur.
Watch our Sulphide Flotation & Gravity Separation Process
The Idaho-Maryland historic grind size is relatively coarse. This saves on power and provides environmental advantages due to less concern with dust and sediment and erosion control.
1) AMEC Foster Wheeler Americas Limited. Technical Report on the Idaho-Maryland Project. June 2017.