Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction2017-04-04T06:57:36-04:00
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Heap Leaching Agglomeration High Clay Ore (3 replies)

1 month ago
redcastle 1 month ago

I've been given the opportunity to acquire a gold deposit that has had some testwork for heap leaching done with decent recovery.

Digging through the historical papers though I've found that the only problem is that it contains a high amount of clay ( kaolinite ) and will definitely require agglomeration.

The testwork indicated that a sample crushed down to 12.5mm required 20kg/t cement but then had a decent percolation rate, however doing some more online research I read that kaolinite can break down in high pH solutions required for cyanide leaching.

Does anyone have any experience in heap leaching high clay ores? It's decent grade and plenty of it there so even if I got a 50% recovery rate I'd be happy, or is this going to just be a nightmare that I'd be better off walking away from

Todd H
1 month ago
Todd H 1 month ago

Clay can be dealt with in a number of ways, agglomeration can be important but again permeability may or may not be an issue (it could be crush size).  The amount of cement you mention is very high and will be costly.

The best way to deal with clay is to blend the ore feed to reduce the impact on any given lift.  You can also simply avoid stacking the high clay ores - send them to waste.  You could also increase the P80 size to reduce the amount of fines generated.  It all depends on what the test work says.

I would recommend doing some column leach tests to define the agglomeration and crush size parameters.


Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com

1 month ago
AJ 1 month ago

Hi There,

As Todd suggests the usual rules apply,

What we normally do is to get a sample, fine crush it to say -6mm, -12mm, and -19mm, agglomerate each of the samples in a concrete mixer (with say 20kg/t cement), test for ball stability (soak some of them for 4-5 days to see if they disintegrate - if they do, you need more cement). If you have a good grade it will support almost any amount of cement, up to where the agglomerates do not remain porous (probably about 100kg/t).(In Australia cement is $300/t so at 20kg/t it adds $6.00 per tonne of ore) If you have say 5g/t (US$41 x 5 = $205/t of ore) - this additional cost is inconsequential especially in a small operation.

We are using 40kg/t cement with a 12g/t head grade and a crush size of - 6mm on a soft high clay gossan ore with success. 

Another thing to consider is your mining strategy, you will need to consider what proportion of fines you will generate when you mine and if you crush and the effect that this will have on your leaching process, its all related.

Kappes, Cassiday and Co have an interesting paper on high clay ores, so go to their website for more info.


Andrew J

1 month ago
redcastle 1 month ago

Cheers for your help andrew, your comments are making me more optimistic about the project, have you got an email If you didn't mind I'd love to chat a bit more about your experiences.


With the crushing I thought about an impact crusher for high throughput and higher percentage of fine crushing, or would agglomeration be too hard and better off with jaw/cone?


Also I had an idea for the low grade 0.8 g/t to crush it to 6mm, dump it in a big vat and manually agitate it with an excavator,  the testwork indicated without agglomeration it got 60% recovery,  but handling the solution could be a problem,  do you think it'd be possible to pump the cloudy water straight through a carbon column, or perhaps some sort of solution settling tank + a bit of floc could make it feasible.

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