Up here we had cyclone efficiency defined by the GRG partition curve. So that’s what we’re talking about right now is will the cyclone keep the gold in the circuit at the designed cut point? So in this case, we see the ore partition curve here. We’ve got the gold partition curve here. So let’s say we’re cutting at 100 micron right here. Well, actually, sorry, this is going to be 110 micron. My apologies.

110 micron – p80 of 110 here. So we’re going to get 80% of the ore partitioned and it looks like in this case, basically 100% of the gold retained in the underflow or extremely close to it. This could be 97%, 98%, 99%, but it’s way up there. If our gold looked different, let’s say it was all very, very, very fine, this gold partition curve could look something like this, for example. And now we’re only retaining 85% or 90% of the gold in the grinding circuit. As I said, this is probably one of the most important parameters, because if you had 100% gold retention in the grinding circuit and nothing got lost, then it really wouldn’t matter how efficient the gravity concentrator is. Then all you’re up against is gold getting smeared onto grinding media, mill liners, hanging up in pump boxes, but it’s trapped there in the circuit.

Now the paper says this effect is minor: as more than 98% of GRG entering the mill remains gravity recoverable after grinding. But I’m going to take exception to that a little bit because 2% GRG can be a lot if you’ve got a high GRG ore and you certainly don’t want to lose that. So having an efficient gravity circuit is definitely important part of that. And there’s a graph down here that just illustrates this a little bit better when we have the gold recovery based on cyclone efficiency. And this is also modeled – we’re assuming a particular partition curve here for the gold, and we can model that and see what happens at different cyclone efficiency. So a 2% difference in cyclone efficiency actually – for the gold retention – actually does have a substantial difference on overall gold recovery in the circuit. So this is one of the reasons that one of the best things an operator can do to improve the gravity circuit is make sure that the cyclones are functioning very efficiently when it comes to gold recovery.

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