Centrifugal devices for micron gold

[Mike Marsupial]

Does anyone have experience with these? They look very effective, but pretty expensive.
https://www.ebay.com.au/itm/Centrif...576728?hash=item3f93fa0918:g:PWoAAOSwa-dWhaoY

I reckon a good 30% of what I run through my sieve set-up just runs back out into the river and down to the ocean. It's very fine. But the set-up does a great job of washing out sludge. Problem is that the fine stuff is kinda suspended in the sludge. Bigger stuff is OK, no problem.

I finished a Miller table this arvo, so tomorrow I'll give it its first run over its glass bed.
I'd like to compare what it does with what a blue bowl can do (and that's a dead easy build), so after testing the Miller table, I'll go and get a big dish (already have a fine collection of funnels) and make a blue bowl too.

One question about the blue bowl; Where should the water inlet be pointed, midway up the side? Top? Bottom?

Cheers

 

[7.62marksman]

When i made mine i had it just below the middle and it seemed to work fine

 

[Mike Marsupial]

Thanks. I'll give that a go.

 

[Satman]

Hi Mike,
Have a look at the knudson bowl. It is a bigger version of what you are looking at.
A mining equipment expert I spoke with several years ago suggested that a inline pressure jig was much better.
You will get compaction on the riffles of the tapered cone and this will effect heavies loss. It will depend on the volume of material that you run and how often you clean up. Mirco gold is still probably best run over a shaker table.
I have looked at shaker tables ex China and they are relatively cheap to what they were several years ago.

Good luck

Matt

 

[Mike Marsupial]

Hi Matt,
Thanks for your post. I've looked at Knudsen bowls and they look pretty good. Apparently there's a bit of an improvement whereby water is injected back through the riffles to lift the lighter stuff back out again. One British site claimed 99% efficiency. You can buy big ones from China for 5 or 6 grand, but they are very big!!!

Just looking at inline pressure jigs now. Thanks for the heads-up.

 

[Mike Marsupial]

Hi again, Matt,

Jigging looks to be a great way to separate finer heavies, but it does seem there's more than a bit of voodoo involved in getting it right.
I strongly suspect the frequency and amplitude of the jigging is key. Higher frequency and lower amplitude for fine particles and the opposite for larger ones. That's probably pretty much common sense.

I found some great info here https://www.911metallurgist.com/blog/gold-mineral-processing-jigs particularly the video with the fella wearing the black beret. But there has to be a much simpler way to apply the principle.

Cheers,
Mike

 

[Satman]

Hi Mike,
Yup the Knudsen bowl with the water feed is better than without from my understanding. I don't believe that they capture 99% though. I was advised not to purchase such a machine. Maybe they do with often cleaning and a constant feed size.
The voodoo with the pressure jig is to have multiple cells (I'd suggest 2 or optimally 3) with different sized ragging in each from course to fine and having the correct pulse and flow rate across each cell. Yes, there will be a bit of tweaking involved to get it right, though working out maximum cell cross flow rates (feed and discharge rate) is a good place to start. Keep it slow and thorough!
Gekko Systems based in Australia produce some fine commercial products for industrial mining and are worth understanding to get an idea of the magic behind their operation.
There are many ways of providing the water surge. For robustness and reliability I suggest a diaphragm type.
If you look at the various videos online the differing pulse system methods and their pros and cons should become apparent.
Again Gekko, are making some high class equipment.
As towards a simpler principal, I am not sure if one exists for high recovery. The worth of the system ultimately will depend on the amount of material that you have to process.
I personally use a 2 cell jig with a tapered long Tom sluice box for extraction with concentrate run over a shaker table, and that is fine for the amount I foresee that I will ever run.
Possibly not the best system, though I don't find any micron gold in the wash.

Well, I think I have totally handed out my secrets now.

Cheers

Matt

 

[HeadsUp]

If youre evaluating fine gold systems then search YouTube for Gemini table.

$35,000 from USA

$25,000 from minteral technologies in QLD

Or there is a guy in Tanzania advertising them for $10,000 USD

Knudsens are very common in a process line while a Gemini is likely to be only found in the gold processing room.

I suspect there is a fibreglass contractor making the table top and supplying it to a few different table builders , I wish I knew who was making them as I would love to own one ...

 

[HeadsUp]

The eBay seller with those mini Knudsen bowls on eBay appears to be the Russian guy who dredges the Loddon river and sells dredges on eBay.

He uses a few different eBay seller stores but they all link back to the same address.

I bought a dive pump off him years ago and it was so shonky it could have killed me if I used it

 

[Satman]

I have had bad dealings with the same Russian, I think. Yes he is dodgy. I got one of his eBay site's shut down for his dodgy dealings.

A Gemini table is great from video results I have seen. Aren't they effectively a two sided shaker table though?

Once I'm back up bush (will be a while, work is keeping me grounded) I'll take some photos and post of my home brew shaker. It took some time to build and tweak, but I can't fault it's gold grabbing ability. I can change table tops to suit the feed material, from slices to course.
I often chase micron gold, as I am into loaming, and not that much into panning all the samples often for very little result.

All the best!

 

[Satman]

Apologies slices should read as slimes.

 

[Mike Marsupial]

Hi Satman,

Ive been following up on some of the things you've mentioned - a couple in particular.

Once I have a REALLY good grasp of the principles involved I'll start thinking of a design for something simple.

Cheers,

Mike

 

[HeadsUp]

I have had bad dealings with the same Russian, I think. Yes he is dodgy. I got one of his eBay site's shut down for his dodgy dealings.

A Gemini table is great from video results I have seen. Aren't they effectively a two sided shaker table though?

Once I'm back up bush (will be a while, work is keeping me grounded) I'll take some photos and post of my home brew shaker. It took some time to build and tweak, but I can't fault it's gold grabbing ability. I can change table tops to suit the feed material, from slices to course.
I often chase micron gold, as I am into loaming, and not that much into panning all the samples often for very little result.

All the best!

If you look closely you will see that many shaker tables have raised ribs or riffles , whereas the Gemini have concave / drop down riffles cut into the table . Maybe thats why the gold is retained better than a shaker table as the water washes over it.

~ I have buckets of concentrates that have very fine flour gold which is problematic for blue bowls or clean up sluices