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Members of the ICMJ Mining Journal Forum may appreciate discussion on the subject of Amalgamation. :)

 

I hope that this thread can develop into a productive discussion on the process of amalgamation.

 

- Geowizard

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Being relatively new, I'd thought about using this to pull gold from my black sand, but the sand left over from my concentrates is not rich enough.  I have a five gallon bucketful of black sand of concentrates that I estimate may have a gram worth of gold left in it.  For that reason, I'd decided not to mess with amalgamtion.  I also don't know the amount of mercury I'd need to charge and put in that sand anyway.  I'm still saving my black sands.  Although I can't remember the exact amount and from what I've read, to make amalgamation worth the effort, the sands need to be rich enough to see the gold with a loop in each sample I take.  My sands are not that rich.

 

I may use amalgamation someday to recover gold, but it will be under a specific set of circumstances, definetly controlled, and after I learn a lot more about it.

 

I appreciate any comments.

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If you are getting good gold on a second run, then 12 mesh is probably too coarse. To get the most out of the blue bowl, you need to separate by screenings the material to be treated into multiple finer size fractions. I've used mine much and if you have too broad a size mixture you will not get good recovery. I can tell you the maker recommends processing a minus 30 mesh fraction.

It seems like minus 12 is not enough size fractions. This is because if you screen to 12 mesh, the flow needed to push 12 mesh black sand and rock will also blow the -30 mesh finer sized gold right out. The water speed is everything. So you have to separate out the finer material and then process it separately with slower water speeds.

What you need to do depends on the amount of real fine gold you have. If you have a lot of real fine gold, like 50 mesh and smaller, You need to produce multiple fractions.

So in that case I would produce a minus 12, a minus 30 and a minus 50. Then process them separately. The water speed needs to be not too fast - it is the separating force of the flowing water that separates the gold (high density) from black and blonde sands (lower density). Smaller fractions can be processed at slower speeds.

If for some reason you don't have a lot of minus 50 gold you may be able to get away with two products, a minus 12 and a minus 30 (and still do them separately with appropriate water speeds. )

My experience is that when you do this properly, you should find the tailings from proper treatment with the blue bowl to be nearly barren.

Sampson Resouces and Geowizard like this

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In fact, I'd not recommend a blue bowl for a production type operation at all. The blue bowl works great, but its not a high speed, maximum production type of operation.

 What I'd suggest is to spend the money to set up an automated operation using a shaker table. shaker tables can capture a wider range of gold sizes in one pass, plus it can easily be set up for automated operation, so you could get it set up and running, then go back and process more material through the wash plant while the cons process themselves.

I don't know how often you clean up, but it wouldn't take that many clean ups at 5 -6 grams loss per clean up to pay for a shaker table system.

That way you'd end up with both the additional gold from the cons and the additional gold from processing more material.

 

Amalgamation certainly works, but often works best in hard rock as the gold is clean. A lot of small placer gold has coatings of iron oxide rust or organic materials. Either of those can prevent the gold from amalgamating properly. The UN stuff is directed mostly at small hard rock miners. Properly done and with reasonable safety precautions, mercury can work well. 

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Hello All,

I use mercury to process my concentrates from my Knudsen centrifuge. Mainly because it's heaps faster then other methods but also because if done right it gets everything.

My material is from hard rock mining and has a wide variety of different sized gold making it very hard to get it all with other methods.

I use a rock tumbler with a few 3/4" and 1" ball bearings to help mix and grind it a bit more. For 5kg of cons I put in about 2oz of mercury, but this depends a lot on the amount of gold in your cons. I tumble it for 1 hour, but half hour is usually long enough.

I do not charge the mercury as I think it is unnecessary and a even greater risk to your health. It seems to work fine without doing it.

If you always keep it underwater, work outdoors with ventilation and wear gloves etc, it is quite safe.

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So when you pull the tumbled cons out of the mixer, then what? what about issues with floured mercury? Grind it up like that and you will have tiny particles of mercury that form. if any mercury remains in the cons when you are finished processing them, you have a haz waste issue, and you will have lost values contained in the floured mercury. Its those fine particles of mercury that give most people who use it fits. Recovering them and the values within them are the problem.

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A couple of thoughts on amalgamation.  Chris, you mentioned that some times amalgamation is not totally effective on placer gold that may be coated with iron oxide or various organics.  I was advised by Bill Bohan that before I take my placer gold to a buyer I should wash it in toilet bowl cleaner to remove any rust [maybe CLR would work better as it would also attack organic compounds]  So I'm thinking that before amalgamation the cons could be washed in a CLR bath to clean them up. 

  Also, Chris, you discussed the problem of "floured" mercury.  Could the cons after amalgamation be roasted in a retort to remove the mercury residue?

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When using mercury on alluvial gold concentrates, the residue/coating can be a problem and will stop the mercury grabbing the gold. To get around this you should add lye, basically a high strength oven cleaner. I use sodium hydroxide which is basically the same thing. Tumble it with 1 cap of NaOH and use distilled water for about 20min when using a small one like me, then empty that out, add fresh water and mercury and tumble again for 30min.

I have not had much trouble with the mercury flowering, if it does happen I add some fresh mercury to help pick it up. When panning the mercury back out I always leave the last 100g of material and put it back into the tumbler with the next batch, just incase there is any that has not been pocked up.

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Thanks for the welcome Geowizard.

Glad you liked the vids.

I drink xxxx gold mate, that way if I don't find any nuggets I can get cans of gold out of my fridge!

I'm in the process of upscaling my processing plant at the moment to handle 4 ton per hour, jaw crusher, ball mill, Knudsen centrifuge. Will do another video once its finished.

I've got some drill intersects of 41g per ton on a new reef I'm working, should be good fun.

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In order to extract fine gold it is not necessary to use mercury. It's expensive, and it is necessary to observe safety measures. It is much easier to finely grind the material and using a centrifugal concentrator, for example Knelson or Icon. And of course the water to spare.

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