Much of the recent and ongoing success in tapping these areas' mineable gold reserves is simply due to the fact that low-grade (to 1.3 grams / tonne gold) near-surface (oxidised) ores can be recovered economically. A new challenge will be to economically recover low-grade sulphide ore by open pit and/or underground methods.Much of the recent and ongoing success in tapping these areas' mineable gold reserves is simply due to the fact that low-grade (to 1.3 grams / tonne gold) near-surface (oxidised) ores can be recovered economically. A new challenge will be to economically recover low-grade sulphide ore by open pit and/or underground methods.