Gravity recovery separates or concentrates minerals and metals on the basis of their density or specific gravity. This technique has been applied since the dawn of time (even the ancients could pan coarse gold from quartz 7 times less dense) and remained largely unchanged until about 40 years ago. In recent years single-g devices such as sluices, shaking tables and spiral concentrators have been replaced, in more demanding applications, with multi-g devices such as centrifuges.
A FLSmiidth – Knelson Concentrator imposing 60g of centrifugal force on a slurry not only magnifies the particle density difference 60-fold, but also allows much higher specific throughputs. A single 400tph Knelson QS48 machine that occupies 9m2 of floorspace replaces a football field of shaking tables or sluices, and does so more efficiently.
Gravity recovery is the cheapest of all mineral extraction processes, using only power and water, and it makes an obvious first choice for any amenable mineral. At Peacocke & Simpson we look first to gravity, in the interests of our clients, and resort to chemical processes only thereafter, and only when necessary. After all, mining is about margins: If gravity can provide a high margin even at relatively low recovery, why introduce chemicals for high recovery at reduced margin?