Let’s have a look at the factors that affect gravity recovery. We’ve got the overall gravity recoverable content of the ore. That’s one number. This is how much GRG – I’m going to refer to gravity recoverable gold as GRG from now on – how much GRG is actually in the ore. Then a related parameter is the size distribution of GRG. So you may have a situation where we’ve got 50% GRG and it’s all 150 micron, or we’ve got the same amount and it’s all 10 micron. And those have a very big difference when it comes to overall gravity recovery. Then we’ve got the recovery efficiency of the circuit, and that’s mostly about the gravity concentrator and the screen associated with it.
So the efficiency can be reduced by inefficient screening, and it can be reduced by inefficient operation of the gravity concentrator. In this case, we’re talking about centrifugal concentrators. Cyclone efficiency: this is likely, to be totally honest, the most important parameter in a gravity circuit. And we’ll get into that in a bit more detail.
We’ve got the fraction of circulating load treated by the gravity concentrator and these two – actually these three are all related to one another and affect one another. Then a bit more of a minor consideration, but still meaningful: the amount of GRG converted to non-GRG in the grinding mill. So this has to do with flattening of gold: having it stick onto mill liners, grinding media. Then we’ve got the gravity section or, you know, gravity circuit availability. And then ultimately we’ve got the gold room efficiency. So you’ve recovered the goal through the gravity concentrator. It goes to the gold room and then that’s going to have – what happens there is going to have an impact on global gold recovery as well.
If you found this video interesting, please visit minerals.seprosystems.com to find the extended video series, as well as additional shorter clips, addressing specific points around gold recovery for milling circuits. Thanks very much for watching.